bangladesh agron. j. 2022, 25(1): 67-73 effect of rice husk on arsenic accumulation in potato plant under different levels of arsenic treated soil t.s. roy1, m.s. rahman2, m. mostofa3, m. nahid4, m.g. khatun5 and m.a. razzaque4 1department of agronomy, 2department of bio chemistry, 4department of agricultural chemistry, faculty of agriculture, sher-e-bangla agricultural university, bangladesh 3tuber crops research centre, bangladesh agricultural research institute, gazipur 5institute of seed technology, faculty of agriculture, sher-e-bangla agricultural university corresponding e-mail: tuhinsuvraroy@sau.edu.bd (received: 10 may 2022, accepted: 22 may 2022) keywords: arsenic, potato flesh, peel, haulm, root, rice husk abstract a pot experiment was conducted in the experimental field of sher-e-bangla agricultural university, dhaka during the period from november, 2020 to may, 2021 to find out the effect of rice husk as an bio-adsorbent to decontaminate as toxicity in potato. the experiment consisted of two factors. factor a: arsenic levels (4) viz., as0: control (0 mg as kg-1 soil), as1: 20 mg as kg -1 soil, as2: 40 mg as kg -1 soil, and as3: 60 mg as kg -1 soil. factor b: rice husk levels (4) viz., r0: control (0 g kg -1 soil), r1: 20 g kg -1 soil, r2: 40 g kg-1 soil and r3: 60 g kg -1 soil. the experiment was laid out in a factorial randomized complete block design with three replications. results revealed that as and/or rice husk had significant effect on arsenic load in different plant parts of potato t. arsenic content in potato tuber flesh, peel, haulm and root gradually increased with the increase of its levels. on the contrary, as content in plant parts decreased with increasing rice husk levels. the soil treated with as1r3 exhibited as accumulation in tuber flesh (0.1070 mg kg -1 fresh weight) and peel (0.443 mg kg -1 fw), respectively. as load in different plant parts was in the sequence: root > haulm > tuber peel > tuber flesh. although, the least as loading in tuber flesh was observed in as1r1, as1r2, as1r3 (range 0.1258-0.1070 mg kg -1 fw) which also showed higher productivity (range 402.67 416.67 g plant-1), but the treatment combination of as1r1 may be suitable for safe potato cultivation in lower level as contaminated soil. therefore, potato growers can grow potato up to 20 mg as kg-1 contaminated soil treated with 20 g rice husk kg1 soil, which contains safe as load than the critical one (0.157 mg as kg -1 fw) for human consumption. so, application of rice husk for potato cultivation may a good option to reduce the arsenic hazards in lower arsenic endemic areas. introduction arsenic (as), the toxic metalloid element, causes terrible health hazards to human beings. around 110 million people in south and south-east asia are suffering from this problem, the magnitude is considered to be the maximum in bangladesh (sanyal, 2005). as-contaminated groundwater used for irrigation may pose serious health hazard to people eating food from irrigated crops (williums et al., 2006). roychowdhury et al. (2003) reported that the contribution of food-chain towards as pollution in human is many folds greater than that of the drinking water. the acute minimal lethal dose of as in adults is estimated to be 1 mg-1kg-1day-1 (das et al., 2004). recent studies suggest that a number of crops and vegetable plant species accumulate significant amount of as. 68 roy et al. the higher as accumulation was observed in aroids, amaranth, radish, lady’s finger, cauli flower, and brinjal, whereas the lower level of as accumulation was observed in potato, beans, green chili, tomato, bitter guard, and turmeric, etc. due to the as-contaminated irrigation water (mandal and suzuki, 2002). as concentration in plants varied from less than 0.01 to about 5.0 g kg-1, whereas the food safety limits of less than 1.0 mg kg-1 (abedin et al., 2002). potato is a world’s single most important tuber crop with a vital role in the global food system and food security (brown, 2005). bangladesh was the world’s 8th largest producer of potatoes with a total production of about 97,44,412 million ton (faostat, 2019). potato consumption as processed and fresh food is also increasing considerable in bangladesh. people living in as affected areas are consuming contaminated potatoes that creates serious health problems. bio-sorption technology includes metal removal performance for industrial waste water. this process is economical and eco-friendly compare with others (lee et al., 2009). it is a conventional technique for metal remediation. bio sorption uses adsorbents derived from non-living biomass like sawdust, rice husk, egg shell etc. and removes toxic metals from industrial waste water and contaminated soil (lee et al., 2013). however, it is necessary to search for appropriate agricultural management practices to minimize the arsenic content in tubers. in this context, the present investigation was mainly axed of as accumulation in potato through rice husk application. materials and methods the pot experiment was conducted at the research field of sher-e-bangla agricultural university. the location of the site is 23.740n latitude and 90.350e longitude with an elevation of 8.2 meter from sea level. the experiment consisted of two factors. factor a: arsenic levels (4) viz., as0: control (0 mg as kg-1 soil), as1: 20 mg as kg -1 soil, as2: 40 mg as kg -1 soil, and as3: 60 mg as kg -1 soil. factor b: rice husk levels (4) viz., r0: control (0 g kg -1 soil), r1: 20 g kg -1 soil, r2:40 g kg -1 soil and r3: 60 g kg -1 soil. the two factors experiment was laid out in a randomized complete block design with five replications. rice husk was collected from a rice mill. the collected soil was sandy loam. soil ph and organic carbons were 5.8 and 0.44%, respectively. the experimental soil of basket was fertilized with a recommended dose of n, p, k, s, zn, b and cowdung @ 575 µg, 345 µg, 750 µg, 108 µg, 18 µg, 8.75 µg and 50 g, respectively, per 10 kg soil (mondal et al., 2011). the certified grade potato tubers of var. courage were used as planting material. collected seed potato tubers were kept at room temperature to facilitate sprouting. the properly sprouted, healthy, and uniform sized (60-70 g) seed potato tubers were planted according to treatment and an entire potato planted in each basket. seed potatoes were planted on an average 5-6 cm depth in the basket. all the intercultural operations and plant protection standards were taken as per tuber crops research centre recommendation. haulm (shoot of potato plant) pulling was done at 90 dap when the majority of plants showed senescence and the tops started drying. after haulm pulling, the tubers were kept under the soil for 10 days for skin hardening. the potatoes of each basket were separately harvested, bagged, tagged and brought to the laboratory for further analysis. all yield contributing parameters were calculated as per tuber crops research centre, bari, bangladesh. potatoes were harvested and packed with labeled net bags according to treatment. haulm (above ground portion), roots and tuber were collected as per treatment. after peeling the tuber, both peel and flesh samples were separated into different labeled packets. the labeled packets were immediately sent to the analytical laboratory of bangladesh council of scientific and industrial research (bcsir), dhaka, where arsenic was determined with an atomic absorption spectrophotometer (hg-aas) following usepa method 1632 (usepa, 2001). the data obtained for different characters were statistically analyzed to observe the significant difference among different treatments. the analysis of variance of all the recorded parameters performed using statistics-10 software. the difference of the means value was separated by least significant difference (lsd) at 5% level of probability (gomez and gomez, 1984). effect of rice husk on arsenic accumulation in potato 69 results and discussion arsenic accumulation in tuber flesh the arsenic load in tuber flesh increased with increasing arsenic level (table 1). a higher concentration of arsenic in soils also created higher absorption of this element by plant parts, which were damaged and restricted plants growth (onken and hossner, 1995). on the contrary, arsenic load in tuber flesh decreased with increasing the rate rice husk application (table 2). the treatment combination of different arsenic and rice husk levels significantly influenced arsenic load in tuber flesh (table 3). the least amount of arsenic load in tuber flesh was observed in as1r3 (0.1070 mg kg -1 fw), whereas, the maximum was recorded in as3r0(0.5063 mg kg -1 fw). the overall arsenic accumulation result showed that high bio adsorbent in soil that occurred more bio sorption process as a result increasing of rice husk levels in a particular concentration of arsenic. arsenic content in tuber flesh drastically decreased by only increasing of rice husk level. rice husk acted as a bioadsorbent in soil and breakdown by microorganism with the presence of soil water and produced cellulosic waste materials viz., acetamido, amido, amino, alcoholic, carbonyl, phenolic, sulphydryl groups, etc., by microorganism with the presence of soil water adsorb arsenic by rice husk from the soil solution and make an intermediate complex between soil colloid and arsenic. rice husk has a close affinity for heavy metal remediation from the aqueous solutions (sud et al., 2008). as a result, when rice husk (bio-adsorbent) levels increased in soil occurred more biosorption process, then the concentration of as decreased in tuber flesh (table 3). table 1. effect of arsenic levels on arsenic accumulation (mg kg-1 fw) in different plant parts of potato at harvest treatments tuber flesh tuber peel haulm root as0 0.0000 d 0.0000 d 0.0000 d 0.0000 d as1 0.1983 c 0.6938 c 4.2545 c 5.1320 c as2 0.2623 b 1.4469 b 5.8308 b 9.0067 b as3 0.3739 a 2.0305 a 8.2600 a 12.821 a lsd(0.05) 0.0103 0.287 0.6987 4.114 cv (%) 5.94 9.30 18.27 7.32 in a columns means having similar letter(s) are statistically similar and those having dissimilar letter(s) differ significantly at 5% level of probability. as0: control, as1: 20 mg as kg-1 soil, as2: 40 mg as kg-1 soil, as3: 60 mg as kg1 soil. arsenic accumulation in tuber peel arsenic content of tuber peel varied significantly with different arsenic levels. the arsenic content of the tuber peel gradually increased with increasing arsenic levels (table 1). the minimum arsenic load in tuber peel was recorded in as1 (0.6938 mg kg -1 fw/), while the maximum in as3 (2.0305 mg kg -1 fw/). arsenic concentration in potato peel was higher than arsenic concentration in potato flesh (norton et al., 2013). arsenic load in tuber peel varied significantly with different rice husk levels. the arsenic load in tuber peel gradually decreased with increasing rice husk levels (table 2). the lowest arsenic load in tuber peel was recorded in r3 (0.5795 mg kg -1 fw) while the maximum in r0 (1.7423 mg kg-1 fw). table 2. effect of rice husk levels on arsenic accumulation (mg kg-1 fw) in different plant parts of potato cv. courage treatments tuber flesh tuber peel haulm root r0 0.3592 a 1.7423 a 6.6577 a 9.1834 a r1 0.1982 b 1.0799 b 4.3503 b 7.0293 b 70 roy et al. r2 0.1604 c 0.7694 c 3.5818 c 5.8994 c r3 0.1167 d 0.5795 d 3.7555 bc 4.8472 d lsd(0.05) 0.103 0.287 0.6987 4.114 cv (%) 5.94 9.30 18.27 7.32 in a columns means having similar letter(s) are statistically similar and those having dissimilar letter(s) differ significantly at 5% level of probability. ns= non-significant, r0-= 0 g rice husk kg-1 soil, r1 =20 g rice husk kg-1 soil, r2= 40 g rice husk kg-1 soil, r3= 60 g rice husk kg-1 soil the treatment combination of arsenic and rice husk levels significantly influenced the arsenic load in potato peel (table 3). the maximum arsenic load in tuber peel was observed in as3r0 (3.8277 mg kg -1 fw) while no accumulation was found in as0 r0 followed by as0 r1, as0r2 and as0r3 because no arsenic was treated in soil and the minimum arsenic load was recorded in as1r3 (0.3443 mg kg -1 fw). table 3 also showed that only by increasing of rice husk level, the accumulation of arsenic decreased in tuber peel. rice husk acted as a bioadsorbent in soil and breakdown by microorganism with the presence of soil water and produced cellulosic waste materials viz., acetamido, amido, amino, alcoholic, carbonyl, phenolic, sulphydryl groups, etc. by microorganism with the presence of soil water adsorb arsenic by rice husk from the soil solution and make an intermediate complex between soil colloid and arsenic. rice husk has a close affinity for heavy metal remediation from the aqueous solutions (sud et al., 2008). high bioadsorbent in soil occurred more bisoroption process as a result increasing of rice husk levels in a particular concentration of arsenic, arsenic content in tuber peel decreased. the experimental results exhibited that arsenic concentration in potato peel was always higher than arsenic concentration in potato flesh. norton et al. (2013) also stated similar trends of arsenic load in tuber flesh and peel. arsenic accumulation in haulm arsenic accumulation in haulm (above ground shoot) varied significantly due to different arsenic levels. table 1 showed that the arsenic load in haulm progressively increased with increasing arsenic levels due to a higher concentration of arsenic in soils also creates higher absorption of this element by haulm. onken and hossner (1995) also indicated similar opinion. arsenic accumulation in haulm varied significantly with different rice husk levels (table 2). the result also demonstrated that arsenic load in haulm decreased with increasing rice husk level. the combination of arsenic and rice husk levels showed significant effect on arsenic loading by haulm (table 3). the maximum arsenic load in haulm was observed in as3r0 (13.360 mg kg -1 fw) while no accumulation was found in as0 r0 followed by as0 r1, as0r2 and as0r3 because no arsenic was treated in soil and the minimum arsenic load was recorded in as1r2 (3.0477 mg kg -1 fw). arsenic accumulation in root accumulation of arsenic in root differed significantly due to different levels of arsenic were treated in soil (table 1). the amount of arsenic load in root progressively increased with increasing arsenic levels. on the contrary, the accumulation of arsenic gradually decreased with increasing rice husk levels (table 2). the combined effect of arsenic and rice husk was also significant on arsenic loading by root. table 9 showed that the maximum arsenic load in root was detected in as3r0 (17.950 mg kg -1 fw) while no accumulation was found in as0 r0 followed by as0 r1, as0r2 and as0r3 because no arsenic was treated in soil and the minimum arsenic load was recorded in as1r3 (3.4497 mg kg -1 fw). table 3. combined effect of arsenic and rice husk on arsenic accumulation (mg kg-1 fw) in different plant parts of potato at harvest treatment combinations tuber flesh tuber peel haulm root as0 r0 0.0000 h 0.0000 k 0.0000 g 0.0000 j as0 r1 0.0000 h 0.0000 k 0.0000 g 0.0000 j effect of rice husk on arsenic accumulation in potato 71 as0r2 0.0000 h 0.0000 k 0.0000 g 0.0000 j as0r3 0.0000 h 0.0000 k 0.0000 g 0.0000 j as1r0 0.4407 c 1.0807 g 5.5943 cd 7.4513 f as1r1 0.1258 g 0.8343 h 3.8697 ef 5.2343 g as1r2 0.1223 g 0.5157 i 3.0477 f 4.3927 h as1r3 0.1070 g 0.3443 j 4.5063 de 3.4497 i as2r0 0.4900 a 2.0610 b 7.6760 b 11.332 c as2r1 0.2070 e 1.6227 d 5.7973 cd 9.2470 d as2r2 0.1923 e 1.2183 f 5.1173 cde 8.1340 ef as2r3 0.1600 f 0.8857 h 4.7327 de 7.3133 f as3r0 0.5063 a 3.8277 a 13.360 a 17.950 a as3r1 0.4627 b 1.8627 c 7.7343 b 13.636 b as3r2 0.3270 d 1.3437 e 6.1623 c 11.071 c as3r3 0.1997 e 1.0880 g 5.7830 cd 8.6260 de lsd(0.05) 0.0207 0.573 1.3973 8.228 cv (%) 3.95 9.30 18.27 7.32 in a colums means having similar letter(s) are statistically similar and those having dissimilar letter(s) differ significantly at 5% level of probability. ns= non-significant, as0: control, as1: 20 mg as kg-1 soil, as2: 40 mg as kg-1 soil, as3: 60 mg as kg-1 soil. r0= 0 g rice husk kg-1 soil, r1= 20 g rice husk kg-1 soil, r2 =40 g rice husk kg-1 soil, r3 = 60 g rice husk kg-1 soil accumulation pattern of arsenic in potato plant parts the maximum accumulation of arsenic was detected in the root (53.6%) as compared to those of other plant parts (figure 1). the roots contained a higher arsenic load than haulm> tuber peel > tuber flesh. haulm accumulated 43.6% arsenic, whereas, tuber only 3.8%. finally, tuber flesh (1.5%) accumulated arsenic very low concentration of this toxic metalloid as compared to all other plant parts. comparison of arsenic loading of different plant parts clearly showed that translocation of arsenic in edible part is relatively lower than the any other plant parts. generally, the distribution arsenic load in plant parts is found to be in the order: root> haulm>tuber. abedin et al. (2002) and sanyal (2005) also observed similar order for arsenic loading in potato plant parts. a plant can only uptake arsenic as as (iii) and as (v). however, it is possible when arsenic complex hydrolysis in soil solution and make as (iii) and as (v) but when bioadsorbent like rice husk was present in the soil the as (iii) and as (v) made a bond with different cellulosic organic complex with soil colloid and produced intermediate complex among arsenic, cellulosic compound and soil colloid. in this regard, the plant could not accumulate arsenic. rice husk has a close affinity for heavy metal remediation from the aqueous solutions (sud et al., 2008). the sorption of heavy metals towards biomaterials is attributed to their constituents, which are mostly carbohydrates, proteins, and phenolic compounds because they carry functional groups, for example, amines, carboxyls, and hydroxyls, which can bind to the metal ions (choi and yun, 2006). 72 roy et al. fig. 1. arsenic accumulation pattern of potato (average value of all treatments). conclusion rice husk had significant effect on arsenic accumulation in plant parts of potato. the soil treated with 60 g rice husk kg-1 soil, decreased 67.51 and 66.73% arsenic accumulation through tuber flesh and peel, respectively compared to without rice husk. among the treatment combinations, although as1r1, as1r2 and as1r3 were found suitable but as1r1 was the appropriate because, in this combination, tuber flesh accumulated only 0.1233 mg as kg-1 fw which is still lesser than the critical level of arsenic contamination (0.15 mg kg-1 fw), so, potato growers can cultivate potato up to 20 mg kg-1 arsenic contaminated soil using 20 g rice husk kg-1 soil. since arsenic content in tuber reduced with increasing the rice husk levels, so further onfarm research trial at arsenic contaminated areas is to be done to find out another bio-adsorbents to minimize more than 80% of arsenic load from potato tuber. acknowledgement this study was supported by sher-e-bangla agricultural university research system (saures). references abedin, m.j., j. feldmann and a.a. meharg. 2002. uptake kinetics of arsenic species in rice plants. plant physiol. 128: 1120-1128. https://doi.org/10.1104/pp.010733. brown, c.r. 2005. antioxidants in potato. amer. j. potato res. 82:163-172. choi, s. and y. yun. 2006. biosorption of cadmium by various types of dried sludge: an equilibrium study and investigation of mechanisms. j. hazard mater 138: 378-383. https://doi.org/10.1016/j.jhazmat.2006.05.059. das, h.k., a.k. mitra, p.k. sengupta, a. hossain, f. islam and g.h. rabbani. 2004. arsenic concentrations in rice, vegetables, and fish in bangladesh: a preliminary study. environ. intl. 30: 383-387. 43.6 % 53.6 % 1.5 % 2.3 % haulm root tuber flesh tuber peel https://doi.org/10.1104/pp.010733 effect of rice husk on arsenic accumulation in potato 73 faostat (fao, statistics division). 2019. statistical database. food and agricultural organization of the united nations, rome, italy. gomez, k.a and a.a. gomez. 1984. statistical procedure for agricultural research. wiley inter-science publication, new york. p.680. lee, h.y., c. jeon, k.j. lim, k.c. hong, j.e. lim, b.s. choi, n.w. kim, j.e. yang and y.s. ok. 2009. adsorption characteristics of heavy metal ions onto chemically modified rice husk and sawdust from aqueous solutions. korean j. environ. agric. 28: 158-164. https://doi.org/10.5338/kjea.2009.28.2.158. mondal, m.r.i., m.s. islam, m.a.b. jalil, m.m. rahman, m.s. alam and m.h.h. rahman. 2011. krishi projukti hatboi (handbook of agro-technology), 5th edition. bangladesh agricultural research institute, gazipur-1701, bangladesh. p.307. norton, g., c. deacon, a. mestrot, j. feldmann, p. jenkins, c. baskaran and a.a. meharg. 2013. arsenic speciation and localization in horticultural produce grown in a historically impacted mining region. environ. sci. technol. 47: 6164-6172. https://doi.org/10.1021/es400720r. onken, b.m. and l.r. hossner. 1995. plant uptake and determination of arsenic species in soil solution under flooded conditions. j. environ. qual. 24: 373–381. https://doi.org/10.2134/jeq1995.00472425002400020022x. roychowdhury, t., t. uchino, h. tokunaga and m. ando. 2002. survey of arsenic in composites from an arsenic affected areas of west bengal, india. food chem. taxicol, 40: 1611-21. sanyal, s. k. 2005. arsenic contamination in agriculture: a threat to water-soil-crop-animal-human condition 92nd session of indian science congress association. ahamadabad, india, 3-7 january, 2005. saud, d., g. mahajan and m. kaur. 2008. agricultural waste material as potential adsorbent for sequestering heavy metal ions from aqueous solutions –a review. bioresour. technol, 99: 6017-6027. https://doi.org/10.1016/j.biortech.2007.11.064. usepa (us environmental protection agency). 2001. method 1632, revision a: chemical speciation of arsenic in water and tissue by hydride generation quartz . willium, p.n., m.r. islam, e.e. adomako, a. raab, s.a. hossain and y.g. zhu. 2006. increase in rice grain arsenic for regions of bangladesh irrigating paddies with elevated arsenic in ground waters. environ. sci. technol. 40: 4903-08. https://doi.org/10.2134/jeq1995.00472425002400020022x bangladesh agron. j. 2014, 17(1): 33-40 yield performance of lentil as a mixed crop with rapeseed m. s. islam1, m. a. islam1*, m. a. begum2, m. maniruzzaman1 and m. a. u. alam1 1on farm research division, bangladesh agricultural research institute, agricultural research station, pabna, 2department of agronomy, bangladesh agricultural university, mymensingh, *corresponding author: amin_bau@yahoo.com key words: lentil, lentil equivalent yield, mixed cropping, rapeseed abstract mixed crop cultivation of lentil and rapeseed could be a promising technology for yield maximization. the field experiment was carried out at multilocation testing site, kashinathpur, pabna during the rabi season of 2011-12 and 2012-13 to verify the performance of rapeseed as mixed crop with lentil at different seeding ratios. the treatment comprises for the experiment were t 1: sole lentil (100%), t 2 : sole rapeseed (100%), t 3 : lentil (100%) + rapeseed (10%), t 4 : lentil (100%) + rapeseed (20%), t 5 : lentil (100%) + rapeseed (30%) and t 6 :farmers’ practice :lentil (100%) + rapeseed (15%). the highest lentil equivalent yield (2.22 t ha-1 in and 2.48 ) and maximum land equivalent ratios (1.27 and 1.28) were observed in t 4 treatment in 2011-12 and 2012-13, respectively.. it was noted that all the mixed cropping systems produced higher equivalent yield and ler than that of their corresponding sole crops. . cost and return analysis showed that the highest net return (tk. 127774 ha-1) was found in t 4 treatment while sole rapeseed gave the lowest net return (tk. 60540 ha-1). net return was always higher under mixed cropping system than that of sole cropping. the highest benefit cost ratio 3.48 was recorded from lentil (100%) + rapeseed (20%) where as the minimum (1.39) from soli rapeseed.. introduction lentil (lens culinaris) is one of the important pulse crops, which ranks the first position regarding area and production in bangladesh (bbs, 2010). it is one of the most important sources of protein both as food and feed. it also produces more stable yield and can be grown with minimum care. lentil is generally grown as sole crop but it can also be grown as mixed or intercrop with maize, mustard, wheat, barley etc. on the other hand, mustard (brassica spp.) is an important oil crop, which also ranks first position among the oil crops in bangladesh (bbs, 2010). mixed cropping is the agricultural practice of cultivating two or more crops in the same piece of land at the same time (ofori and stern, 1987; anil et al., 1998). it offers effective weed suppression, pest and disease control, and use of soil resources under organic farming systems (bulson et al., 1997; theunissen, 1997; jensen et al., 2005). an ideal intercropping or mixed cropping system should aim to i) produce higher yields per unit area through better use of natural resources, minimizing the incidence of insect pests, diseases weeds and improving the nitrogen economy in legume associations, ii) offer greater stability and crop insurance in production under aberrant weather condition, iii) meet the domestic need of farmers and animal iv) provide an equitable distribution of farm resources (ali, 1990). so, this trial was planned to evaluate the technological feasibility and economic validity of mixed cropping lentil with rapeseed at different seeding rates of rapeseed. materials and methods the experiment was carried out at mlt site, kashinathpur, pabna in the rabi season of 2011-12 and 2012-13. the soils of the experimental areas belong to the high ganges river flood plain under aez-11. mailto:amin_bau@yahoo.com 34 islam et al. the soils of the experimental plots were sandy clayey loam in texture. the experiment was laid out in randomized complete block (rcb) design with six dispersed replications. it was consisted with six treatments as follows: t1: sole lentil (100% lentil), t2: sole rapeseed (100 % rapeseed), t3: lentil (100%) + rapeseed (10%), t4: lentil (100%) + rapeseed (20%), t5: lentil (100%) + rapeseed (30%) and t6: lentil (100%) + rapeseed (15%). seed rate 30 kg ha -1 for lentil and 10 kg ha-1 for rapeseed was considered for crop, respectively. to obtain 10, 15, 20, 30% rapeseed, amount of seed mixed with lentil was calculated as 1, 1.5, 2.0 and 3.0 kg ha-1. the calculated amounts of rapeseed were mixed with 30 kg of lentil seeds separately for achieving different treatment combinations (i.e. t3, t6, t4 and t5 treatments). seeds of lentil (barimasur7) and rapeseed (barisarisha14) were sown on 10th to17th november in 2011 and 2nd to 5th november in 2012 as broadcast. the unit plot size was 7.5m x 4m. the lands were fertilized with 19, 16, 20, 7, 1.5 and 1.5 kg n-p-k-s-zn-b ha-1 respectively for sole lentil and mixed cropping and 115, 34, 43, 27, 2.5 and 2.5 kg n-p-k-s-zn-b ha-1 for sole rapeseed. all the fertilizers of entire amount was applied during final land preparation as basal except t2 (sole rapeseed) as one third urea was applied as top dress at about 30 das on 20th to 22nd december, 2011 and 2nd to 5th december, 2012. the treatments were evaluated in terms of land equivalent ratio (ler) using the following formula of willey (1981). ler = ------------------------------------ + ------------------------------------- also, rapeseed yields were converted into lentil equivalent yield as per anjeneyula et al. (1982). lentil yield equivalent y = ----------- where, y l = yield of lentil, pl and pm = market prices of lentil and rapeseed, respectively. the recorded data were statistically analyzed following gomez and gomez (1984). all types of variable production cost are recorded to find out the benefit cost ratio (bcr). results and discussion yield and yield attributes of lentil the results revealed that most of the yield attributes of lentil were significantly influenced due to mixed cropping with rapeseed except plant population (table 1). higher plant height (48.10 cm in 2011-12 and 50.63 cm in 2012-13) was obtained from t 1 treatment followed by t3. the maximum number of pod plant-1 (57.18 in 2011-12 and 46.55 in 2012-13) was recorded in t1 which was statistically identical to t3, t4 and t6 treatments and the lowest number of pod plant -1 from t5 treatment. pods plant -1, number of seeds pod-1 was found significant in all the treatment combination in 2011-12 but statistical similarity in 2012-13 except t 5 treatment. in 2011-12 cropping season, 1000seed weight was statistically similar in t 1, t3, t4 and t6 but numerically higher 1000 seed weight (18.55g) was obtained from t 3 and the lower (17.87g) from t5 treatment where as in 2012-13 while maximum in t 1 (18.91 g) followed by t 3 (18.33 g), t4 (18.32 g) and t6 (18.23 g) and the lowest (17.26 g) in t5 treatment. t1 treatment produced the highest seed yield (1.90 t ha-1) in 2011-12 and 2.04 t ha-1 in 2012-13. the maximum seed yield in t1 might be due to cumulative effect of yield contributing characters i.e. number of pod plant-1, number of seeds pod-1 and 1000seed weight. yield of intercropped lentil yield of solecropped lentil yield of intercropped rapeseed yield of solecropped rapeseed yl x pl pm 35 mixed cropping of lentil with rapeseed table 1. seed yield and yield attributes of lentil as a mixed crop with rapeseed treatments plant height (cm) plant population m-2 number of pods plant-1 2011-12 2012-13 2011-12 2012-13 2011-12 2012-13 t1 48.10 50.63 119.96 126.1 57.18 46.55 t3 42.93 45.19 114.57 124.1 53.80 45.78 t4 42.29 44.52 118.48 123.1 48.56 45.70 t5 39.16 41.22 110.70 121.2 39.44 43.84 t6 40.36 42.48 114.97 122.2 51.33 44.42 lsd (0.05) 2.512 0.643 ns ns 11.74 0.198 cv (%) 3.99 6.26 10.33 4.25 12.66 6.8 table 1. (continued) treatments number of seeds pod-1 1000seed weight (g) seed yield (t ha-1) 2011-12 2012-13 2011-12 2012-13 2011-12 2012-13 t1 1.68 1.65 18.32 18.91 1.90 2.04 t3 1.75 1.65 18.55 18.33 1.73 1.91 t4 1.72 1.65 18.25 18.32 1.80 1.91 t5 1.67 1.55 17.87 17.26 1.57 1.59 t6 1.70 1.65 18.53 18.23 1.78 1.82 lsd (0.05) 0.053 0.038 0.241 0.107 0.038 0.174 cv (%) 2.47 2.89 3.69 2.50 7.10 5.60 yield and yield attributes of rapeseed data as presented in the table 2 revealed that yield and yield contributing characters of rapeseed were differed significantly different. there was an increasing trend of plant population with the increase of seed ratio in all the treatments. the maximum plant population (84.94 and 99.40) was observed in t2 treatment followed by t5 and the lowest plant population (10.40 and 22.21) from t3 treatment in 2011-12 and 2012-13,respectively. the maximum number of siliqua plant-1 (45.00) were found in t3 which was statistically similar to t6, t4 and t5 and the minimum (30.43) from t2 treatment during 2011-12. similar trend was observed in 2012-13. in 2011-12, the highest number of seeds siliqua-1 (32.34) was obtained from t4 followed by t6 as well as the lowest (29.83) was recorded from t 2. more or less similar results were recorded in 2012-13. from two years result showed that there was no significant difference among the treatment regarding 1000seeds weight (g) but numerically higher 1000seeds weight (2.93 g in 2011-12 and 2.79 g in 2012-13) was observed in t3 followed by t2 and t6 but the lower (2.75 g in 201112 and 2.73 g in 2012-13) from t 5 treatment. the maximum seed yields 1.65 t ha -1 and 2.12 t ha-1 were obtained in t2 followed by t5 due to higher plant population where as the minimum seed yield (0.50 t ha1 in 2011-12 and 0.55 t ha-1 in 2012-13) was obtained from t3 treatment, which were statistically similar to t6. table 2. seed yield and yield attributes of rapeseed as a mixed crop with lentil treatments plant height (cm) plant population m-2 no. of siliquae plant-1 2011-12 2012-13 2011-12 2012-13 2011-12 2012-13 t2 74.71 82.64 84.94 99.40 30.43 30.48 t3 78.16 86.46 10.40 22.21 45.00 34.50 36 islam et al. t4 76.13 84.22 20.94 30.80 39.63 33.92 t5 72.72 80.44 33.37 39.20 37.50 31.14 t6 78.42 83.44 16.33 26.01 41.73 33.68 lsd (0.05) 0.975 2.19 2.776 2.257 9.357 2.063 cv (%) 7.63 6.45 5.77 6.87 12.89 5.70 table 2. (continued) treatments no. of seeds siliqua-1 1000-seed weight (g) seed yield (t ha -1) 2011-12 2012-13 2011-12 2012-13 2011-12 2012-13 t2 29.83 28.66 2.90 2.77 1.65 2.12 t3 30.67 29.98 2.93 2.79 0.50 0.55 t4 32.34 28.38 2.77 2.76 0.53 0.72 t5 30.20 27.64 2.75 2.73 0.62 0.82 t6 30.90 29.92 2.80 2.77 0.50 0.63 lsd (0.05) 0.059 1.668 ns 0.042 0.059 0.261 cv (%) 5.11 4.30 7.72 3.65 6.29 12.08 lentil equivalent yield and land equivalent ratio (ler) data presented in the table 3 revealed that the equivalent yield of lentil was differed from each other among the treatments in both the consecutive years. the maximum lentil equivalent yield (2.22 t ha-1) was obtained from t4 followed by t6 and t3 and the lowest lentil (1.30 t ha -1) in t2 treatment in 201112. similar trends were observed in 2011-12. the highest lentil equivalent yield (2.48 t ha-1) was obtained from t4 followed by t6 and t3 and the lowest lentil equivalent yield (1.67 t ha -1) was recorded in t2 treatment. it was noted that all the mixed cropping system produced higher equivalent yield than that of their corresponding sole crops. results from both the years indicated that t4 treatment was found higher yield advantageous as well as profitable over other treatments. similar observations in different mixed/intercropping systems were reported by other authors (ali et al., 2007, patra et al., 2000; islam et al., 2008 and alom et al., 2008). the maximum land equivalent ratio (ler) 1.27 and 1.28 were observed in 2011-12 and 2012-13, respectively from the t 4 treatment followed by t6 . it is noted that all the mixed cropping systems showed higher ler than sole crop. it could be said that a farmer may increase his land use efficiency by 27 to 28% from mixed cropping systems from growing one hectare of land than that of their traditional sole crops cultivation. the results are in agreement with that of santalla et al. (2001), basak et al. (2006), razzaque et al. (2007) and alom et al. (2008). table 3. lentil equivalent yield and land equivalent ratio (ler) of mixed cropping entil with rapeseed treatments 2011-12 2012-13 seed yield (t ha-1) lentil equivalent yield (t ha-1) ler seed yield (t ha-1) lentil equivalent yield (t ha-1) ler lentil rapeseed lentil rapeseed t1 1.90 1.90 1.00 2.04 2.04 1.00 t2 0.00 1.65 1.30 1.00 2.12 1.67 1.00 t3 1.73 0.50 2.13 1.21 1.91 0.55 2.34 1.20 t4 1.80 0.53 2.22 1.27 1.91 0.72 2.48 1.28 t5 1.57 0.62 2.05 1.20 1.59 0.82 2.23 1.17 t6 1.78 0.50 2.18 1.24 1.82 0.63 2.32 1.19 cost benefit analysis 37 mixed cropping of lentil with rapeseed data of cost and return analysis (average of two years) are presented in the table 4. it showed that the highest gross return (tk.164500 ha-1) and net return (tk.127774 ha-1) were found maximum in t4 followed by t6 and t3 while sole rapeseed produced the lowest gross return (tk.103950 ha -1) as well as net return (tk.60540 ha-1). the cost of cultivation was found higher in sole rapeseed cultivation as it required more fertilizers, irrigation and labour costs than that of lentil cultivation. net return was higher than mixed cropping system than that of sole cropping. many investigators also reported higher net return in mixed/intercropping systems than sole crop (quayyum and maniruzzaman, 1995; sarker and pal, 2004; basak et al., 2006; razzaque et al., 2007; pyare et al., 2008 and alom et al., 2008). the highest benefit cost ratio (3.48) was recorded from t 4 where as the minimum bcr (1.39) from t2 treatment. table 4. cost and return analysis obtained from the experimentation (average of two years) treatments lentil equivalent yield (t ha-1) gross return (tk. ha-1) total cost (tk. ha-1) net return (tk. ha-1) benefit cost ratio (bcr) t1 1.97 137900 36464 101436 2.78 t2 1.49 103950 43410 60540 1.39 t3 2.24 156450 36595 119855 3.28 t4 2.35 164500 36726 127774 3.48 t5 2.14 149800 36857 112943 3.06 t6 2.25 157500 36661 120840 3.30 price of input (tk. kg-1) price of output (tk. kg-1) seed 110 lentil grain 70.0 urea 20.0 rapeseed 55.0 tsp 24.0 mop 15.0 gypsum 10.0 znso 4 130.0 boric acid 130.0 conclusion lentil equivalent yield was increased with the increase in percent of rapeseed up to 20% with 100% lentil and thereafter it declined with further increment in seeds. all the mixed crop combinations showed higher gross return as well as net return than the respective sole crops. considering the yield and return it can be concluded that treatment t 4 viz. 100% lentil with 20% rapeseed (30 kg lentil with 2.0 kg rapeseed per hectare) was the most profitable one compared to other treatments when grown as mixed crop. furthermore, mixed cropping was found more profitable than the sole. references ali, m. 1990. pigeonpea: cropping systems. the pegionpea cab international icrisat, patancheru, a.p. 502324, india. pp.281-282. ali, m. o., m. j. alam, m. s. alam, m. a. islam and m. shahin-uz-zaman. 2007. study on mixed cropping mungbean with sesame at different seeding rates. intl. j. sustain. crop prod. 2: 74-77. 38 islam et al. alom, m. s., n. k. paul, and m. a. quayyum. 2008. performance of hybrid maize (zea mays l.) under intercropping systems with mungbean (vigna radiata l.) in different planting methods. saarc j. agri. 6: 73-82. altieri, m. a. 1999. the ecological role of biodiversity in agroecosystems. agric. ecosys. environ.74 : 19-31. altieri, m. a., d. k. letourneau and j. r. davis. 1983. developing sustainable agroecosystems. biosci. 33: 45-49. anil, l., j. park, r. h. phipps and f. a. miller. 1998. temperate intercropping of cereals for forage: a review of the potential for growth and utilization with particular reference to the uk. grass forage sci 53: 301-317. anjeneyula, v. r., s. p. singh and m. ali. 1982. effect of competition free period and technique and pattern of pearl millet planting in growth and yield of mungbean and total productivity in solid pearl millet and pearl millet/mungbean intercropping systems. indian j. agron. 27: 219-226. bangladesh bureau of statistics (bbs). 2010. yearbook of agricultural statistics of bangladesh. reproduction, documentation and publication wing, bbs, secretariat, dhaka. basak, n. c., s. m. a. hossain, i. islam and n. i. bhuiyan. 2006. intercropping wheat with groundnut at variable plant population bangladesh j. agril. res. 31: 207-215. bulson, h. a. j., r.w. snaydon and c. e. stopes. 1997. effects of plant density on intercropped wheat and filed beans in an organic farming system. j agr. sci 128: 59-71. chowdhury, s. l. 1981. recent studies in intercropping systems on proceedings of the india-some thoughts, some results. in: proceed. intl. workshop intercrop., 10-13 january, 1979 icrisat, patancheru, a.p. 502324, india. pp.299-305. gomez, k. a. and a. a. gomez. 1984. statistical proc. agric. res. 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http://www.cabdirect.org/search.html?q=do%3a%22plant+archives%22 http://www.cabdirect.org/search.html?q=do%3a%22plant+archives%22 39 mixed cropping of lentil with rapeseed razzaque, m. a., s. rafiquzzaman, m. m. m. bazzaz, a. ali and m. m. r. talukdar. 2007. study on the intercropping groundnut with chilli at different plant populations. bangladesh j. agril. res. 32(1): 3743. santalla, m., a. p. rodino, p. a. casquero and a. m. de ron. 2001. interactions of bush bean intercropped with field and sweet maize. european j. agron. 15: 185-196. sarkar, r. k. and p. k. pal. 2004. effect of intercropping rice (oryza sativa) with groundnut (arachis hypogaea) and pigeonpea (cajanas cajan) under different row orientations on rainfed uplands. indian j. agron. 49(3): 147-150. scherr, s. j. and j. a. mcneely. 2008. biodiversity conservation and agricultural sustainability: towards a new paradigm of ‘ecoagriculture’ landscapes. phil. trans. r. 363: 477-494. thrupp, l. a. 2002. linking agricultural biodiversity and food security: the valuable role of agrobiodiversity for sustainable agriculture. intl. aff. 76: 283-297. theunissen, j. 1997. intercropping in field vegetables as an approach to sustainable horticulture. outlook agr. 26: 9599. willey, r. w. 1981. a scientific approach to intercropping research. in: proc. intl. workshop intercrop. 10-13 january, 1979, icrisat, patancheru, a.p. 502324, india. pp.4-14. willey, r. w. and m. r. rao. 1981. a competitive ratio for quantifying competition between intercrops. expt. agric. 16: 117-125. 40 islam et al. bangladesh agron. j. 2016, 19(2): 11-20 system productivity of potato + maize intercropping as affected by sowing date a.a.begum1, m.s.u.bhuiya2, s.m.a. hossain2, amina khatun3, s.k. das4and m.y. sarker5 1agronomy division, bari, 2 department of agronomy, bau, 3 rfs division, brri, 4bangladesh betar, dhaka and 5bjri, dhaka *corresponding author: luckyshamol6869@gmail.com key word: sowing date, shading, lai, dm, cgr, equivalent yield, potato, maize, intercropping abstract the experiment was conducted at agronomy research field, bangladesh agricultural research institute (bari), gazipur during 2009-2010 to find out suitable sowing time of maize in potato + maize intercropping for maximum yield and economic return. treatments of the experiment were: t1= simultaneous sowing (ss) of potato and hybrid maize (hm), t2= ss of potato and composite maize (cm), t3= hm sown 10 days after potato planting (dapp), t4= cm sown 10 dapp, t5= hm sown 20 dapp, t6= cm sown 20 dapp, t7= hm sown 30 dapp, t8= cm sown 30 dapp, t9= hm sown 40 dapp, t10 = cm sown 40 dapp, t11= sole potato, t12= sole hm and t13= sole cm. the result revealed that sole potato and maize produced the highest yield, lai, tdm and cgr. the hm showed better performance than cm. the highest equivalent yield and monetary return indicated that potato + hm sown 30 dapp intercropping was the most productive and profitable. introduction intercropping is an important tool for getting higher productivity per unit area of land and it improves the food security (mahfuza et al., 2012). intercropping system becomes productive and economical only when it is done properly by selecting compatible crops (begum et al., 2010), by shifting the period of peak demand for growth resources through changing the time of sowing of the component crops (santalla et al., 1999) and when their component crops differ in photosynthetic pathway, growth habit, growth duration and demand for growth resources (islam et al., 2007). potato and maize may be grown as intercrop as they have different photosynthetic pathway, growth habit, growth duration and demand for growth resources. potato is now becoming an important food for ensuring food security in bangladesh. conversely, maize (zea mays l.) is the third most important food grain for human after rice and wheat. maize in bangladesh is becoming an important crop in the rice-based cropping pattern. in recent years maize is gaining popularity among the farmers mainly due to high yield, more economic return and versatile uses. sowing of component crops in different times is an important agronomic approach in intercropping systems but has not been extensively studied. intercropping of 20-35 days after the planting of potato can bring very high profit, providing 20-21 t ha-1 maize equivalent yield within five months (cimmyt office in bangladesh, 2006). however, information relating sowing time of potato and maize in an intercropping system is very scarce. so, to understand the nature and extent of competition and complementarities of component crops, the experiment was undertaken to find out suitable sowing date of maize in potato maize intercropping for getting higher yield and economic return. mailto:luckyshamol6869@gmail.com 12 begum et al. materials and methods the experiment was conducted at the agronomy research field of bari, gazipur during the rabi season of 2009-2010. the soil of the experimental field was chhiata clay loam having ph 6.49, organic matter 1.08%, total n 0.034(%), potassium 0.18 meq/100g soil, phosphorus 13.5 ppm, sulphur 14.5 ppm, zinc 1.13 ppm and boron 0.21 ppm. maximum and minimum temperatures ranged from 24.11 to 35.13 and 11.21 to 25.450c, respectively, during the study period. average monthly rainfall for this period was 45.00 mm where maximum rainfall was recorded 228.00 mm and minimum 8.00 mm. thirteen treatments were as follows: t1= simultaneous sowing (ss) of potato and hybrid maize (hm), t2= ss of potato and composite maize (cm), t3= hm sown 10 days after potato planting (dapp), t4= cm sown 10 dapp, t5= hm sown 20 dapp, t6= cm sown 20 dapp, t7= hm sown 30 dapp, t8= cm sown 30 dapp, t9= hm sown 40 dapp, t10= cm sown 40 dapp, t11= sole potato, t12= sole hm and t13= sole cm. the experiment was laid out in randomized complete block design with three replications. the size of a unit plot was 6.0 m  5.0 m. potato var. bari alu-8 (cardinal) and maize var. bari hybrid maize-7 and bari maize-7 (composite) were used in the experiment. potato was planted on 20 november 2009. sole potato and sole maize were also planted on the same date. potato was planted with 60 cm × 25 cm spacing in sole and 75 cm  20 cm spacing in intercrop situation. maize was sown in 75 cm  20 cm spacing both in sole and intercrop situation. in intercrop treatments, one row of maize accommodated in between two rows of potato. for sole potato, sole hybrid maize and sole composite maize fertilizers were applied @ n180p40k180s20zn6b1.2, n260p72k148s48zn4b2 and n160p50k100s40zn4b2 kg/ha, respectively (barc, 2005). for intercrop fertilizers were applied @ n320p73k170s50zn6b2 kg/ha (akhteruzzaman et al., 2008). the source of n, p, k, s, zn and b was urea, triple super phosphate (tsp), muriate of potash (mop), gypsum, zinc sulphate and boric acid, respectively. in case of sole potato, half amount of urea, mop and the whole amount of tsp, gypsum, zinc sulphate and boric acid were applied at the time of final land preparation. remaining amount of urea and mop were applied at 30 days after planting (dap). for sole maize, one-third of urea and whole amount of other fertilizers were applied at the time of final land preparation. remaining amount of urea was applied in two equal splits as side dressing at 30 and 55 days after sowing (das). in case of intercrop, onethird (1/3) urea and of all other fertilizers were applied as basal. onethird urea and rest of all other fertilizers were side dressed at 30 dap of potato and rest of urea was side dressed just after potato harvest followed by irrigation. four irrigations were given during the cropping period. first irrigation was given after potato planting, second at 30 dapp, third at 55 dapp and lastly at 95 dapp (just after potato harvest). fungicide (dithane m-45) was sprayed at every 10-day intervals beginning from 25 to 70 dap for preventing potato disease. shading (%) was computed by converting photo synthetically active radiation (par) and measured by par ceptometer (model – lp-80, accu par, decagon, usa) at 60, 68, 76, 84 and 92 dapp at around 11:30 a.m. to 13:00 p.m. par was calculated using the following equation and expressed in percentage (ahmed et al., 2010): 100 incpar partincpar int(%)par    where, par int = intercepted par, par inc = incident par and part = transmitted par shading (%) on underneath crop, par int (%) by upper storied crop 13 system productivity of potato + maize intercropping as affected by sowing date plants were sampled at 15 day intervals from 30 days to maturity for potato and 20 day intervals from 30 to 130 days after sowing for maize and green leaf area was measured by an automatic leaf area meter (model: li-300, usa). plant materials were oven dried at 700c to a constant weight and dry weight taken. crop growth rate of the component crops was computed by using the following equation (gardner et al., 1985): crop growth rate (cgr) = (w2-w1) / (t2-t1) where, w = weight of dry matter unit-1 area and t = time (days) and the subscripts 1 and 2 indicate measurements at time t1 and t2, respectively. potato was harvested on 24 february 2010 (95 dap) and maize was harvested at 132-146 das. yield of both crops were taken from whole plot. potato equivalent yield was computed by converting yield of intercrops on the basis of prevailing market price of individual crop following the formula of bandyopadhyay (1984) as given below: potato equivalent yield = yip + (yim  pm) / pp where, yip = yield of intercrop potato, yim = yield of intercrop maize, pp = market price of potato and pm = market price of maize. collected data of both the crops were analyzed statistically and the means were adjudged using dmrt. economic analysis was also done considering local market price of harvested crops. results and discussion plant shading (%) shading given by maize plants on underneath potato crops over time differed significantly at all the time intervals (fig. 1). shading increased progressively up to potato harvest. the highest shading (80%) was observed in t1 (simultaneous sowing) at 90 dap (days after planting) and the lowest shading in t9 (52%) followed by t10 (when maize sown 40 dapp), t7 & t8 (maize sown 30 dapp). similar trend was observed at all the intervals. shading (2070%) was occurred by maize canopy on underneath potato crop during tuber bulking period (40-80 dap) when maize was sown simultaneous with potato and 10 or 20 dap of potato. on the other hand, 040 % shading given by maize canopy during tuber bulking period (40-80 dap) when maize was sown 30 and 40 dapp and tuber bulking could start before shading given by maize plant and the degree of shading from 40 dap onward was not exceed over 40 % and more than 60 % of the total incoming solar radiation transmitting through the maize canopy which was sufficient for continued rapid tuber bulking. the result revealed that planting date of maize intercropped with potato, maize sown on 30 days after planting of potato is suitable for intercropping. maize grain yield was drastically reduced might be due to hot temperature at later growth stage. ifenkwe and odurukwe (1990) reported that potato yields increased with delayed sowing in association with maize while maize yields decreased as its sowing date was delayed. functional relationship between shading occurred by maize plant and tuber yield of potato indicated that tuber yield was negatively correlated to shading occurred by maize canopy in potato maize intercropping system (fig. 2). the functional relationship suggested that 93% (r2=0.928) of the variation in yield of potato could be explained from the variation in shading. on an average, yield of potato could be decreased at the rate of 0.311 t ha-1 with an increase in 1% of shading. 14 begum et al. leaf area index of potato and maize leaf area development in intercropped potato and maize are presented in figs. 3 and 4. the lai in potato and maize varied significantly in all the intervals up to harvest. the lai increased sharply with the advancement of time up to 60 dap in potato and 110 das in maize and thereafter decreased might be due to leaves senescence. the highest lai (2.60) was observed in t11 (sole potato) at 60 dap. lais of potato were similar in monoculture as well as when maize was intercropped with potato 30 and 40 dapp and markedly differed when maize was intercropped simultaneous, 10 and 20 dapp. 0 10 20 30 40 50 60 70 80 90 30 40 50 60 70 80 90 s h a d in g (% ) days after planting fig. 1 shading (%) on potato by maize canopy in potato + maize intercropping systern over days after planting of potato ss of potato & hm ss of potato & cm hm sown 10 dapp cm sown 10 dapp hm sown 20 dapp y = -0.3116x + 28.138 r² = 0.9285 0 5 10 15 20 25 0 20 40 60 y ie ld o f p o ta to (t h a -1 ) shading (%) fig. 2 functional relationship between shading ocurred by maize plant and tuber yield of potato in potato maize intercropping 15 system productivity of potato + maize intercropping as affected by sowing date more or less similar result was observed by islam (2002). lai of maize was highest in monoculture which was closer to the lai of maize grown simultaneously. but lai of maize reduced considerably when it was sown 10, 20, 30 and 40 dapp. similar result was reported by watiki et al. (1993) when cowpea was grown in association with maize. in all treatments the lai of hybrid maize were higher than those of composite maize. it might be due to varietal character (alam, 2003) due to different lai in different varieties of maize. total dry matter of potato and maize total dry matter (tdm) of intercropped potato and maize increased progressively over time and there was significantly difference in the pattern of biomass accumulation at different sowing date of maize (fig. 5 and 6). tdm increased sharply up to 60 dap and 110 das in potato and maize, respectively, and then increased slowly up to harvest. sole potato produced higher tdm than any other intercropped potato. intercropped potato faced different levels of shading from different sowing dates of maize and subsequently accumulated lower dry matter (kephart et al., 1992). the higher tdm of maize was found in monoculture and simultaneous sown with potato did not differ markedly but sharp difference occurred when maize was sown 10, 20, 30 and 40 dapp. total dry matter accumulation in pure stand maize and earlier sown were higher than those sown in later and the lowest dry matter was found when maize was sown 40 dapp. earlier sowing of maize showed better competitiveness of nutrients over late sown maize and reduced dry matter of late intercropped maize. the tdm of potato and maize was found positively correlated with tuber yield (r = 0.99) and grain yield (r = 0.67), respectively. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 30 45 60 75 harvest l a i day after planting fig. 3. lai of potato in potato + maize intercropping ss of potato & hm ss of potato & cm hm sown 10 dapp cm sown 10 dapp hm sown 20 dapp cm sown 20 dapp 0.0 1.0 2.0 3.0 4.0 5.0 30 50 70 90 110 harvest l a i days after sowing fig. 4. lai of maize in potato + maize intercropping ss of potato & hm ss of potato & cm hm sown 10 dapp cm sown 10 dapp hm sown 20 dapp cm sown 20 dapp 16 begum et al. crop growth rate of potato and maize crop growth rate of potato increased sharply up to 60 dap and thereafter declined rapidly till harvest. crop growth rate of intercropped potato with maize sown at 30 and 40 days after potato planting were similar to that of sole potato. but it was significantly lower when maize was sown simultaneously or 10 and 20 dapp. it might be due to reduction of leaf area and lower light availability to underneath potato canopy. demagante and zaag (1988a) reported that early shading (planting on wards) had a strong detrimental effect on tuber bulking rate with more shad. irrespective of sowing date, cgr of maize (both varieties) increased progressively with time and reached peak at 110 das then declined till harvest in monoculture. similar result was found by alom (2007) and the earlier sowing of maize (simultaneous, 10 and 20 days after potato planting) reached peak at 110 das and delayed sown maize (30 and 40 dapp) reached peak at 70-90 das. earlier attainment of peak in dry matter accumulation in plant at late sown maize might be due to shortening of growth period with increase of temperature at later growth stage. there was a trend for higher cgr in sole cropping compared to the intercropped due to less competition among the plants for growth resources like nutrient, air, moisture, solar radiation etc. kumar et al. (2000) also reported similar results. the cgr of potato and maize was found positively correlated with tuber yield (r = 0.98) and grain yield (r = 0.68), respectively. 0 200 400 600 800 1000 30 45 60 75 harvest t d m (g m -2 ) day after planting fig. 5. tdm of potato in potato + maize intercropping ss of potato & hm ss of potato & cm hm sown 10 dapp cm sown 10 dapp hm sown 20 dapp cm sown 20 dapp hm sown 30 dapp cm sown 30 dapp hm sown 40 dapp cm sown 40 dapp sole potato 0 500 1000 1500 2000 2500 3000 30 50 70 90 110 harvest t d m (g m -2 ) days after sowing fig. 6. tdm maize in potato + maize intercropping ss of potato & hm ss of potato & cm hm sown 10 dapp cm sown 10 dapp hm sown 20 dapp cm sown 20 dapp hm sown 30 dapp 17 system productivity of potato + maize intercropping as affected by sowing date yield and yield components of potato yield and yield components of potato were significantly affected in potato + maize intercropping (table 1). significant variation was observed in number of stems m-2, number of tubers hill-1, tuber weight hill-1 and tuber yield. the maximum number of stems m-2 was observed in sole potato (t11) which was statistically similar with maize sown after 30 and 40 days of potato planting (t7, t8, t9 and t10) and the lowest in potato + hm sown simultaneously (t1). similar trend was observed in number of tubers hill-1, tuber weight hill-1 and tuber yield. the maximum tuber yield of potato was recorded in sole potato (22.50 t ha-1) which was statistically similar with maize sown after 30 and 40 days of potato planting and it might be due to the early– bulging period of tuber which was shading free and cooling effect of shading during later growth stage of potato which favoured tuber bulging for longer period and ultimately increased tuber yield in maize sown 30 and 40 dapp. kuruppuarachchi (1990) also observed similar results in potato + maize intercropping. he reported that higher tuber yield where maize was sown delayed after potato planting. maize sown simultaneously with potato gave the lowest tuber yield which was statistically similar with maize sown 10 dapp. it might be due to lower light transmission during the tuber bulging period which reduced tuber yield. tuber yield in different treatments were attributed to the cumulative effect of yield components. table 1. yield and yield components of potato in potato maize intercropping as affected by sowing date of maize treatments hills m-2 (no.) stems m-2 (no.) tubers hill-1 (no.) tubers wt. hill-1 (g) tuber yield (t ha-1) t1= ss of potato & hm 6.00 20.00d 5.50c 301.88d 13.10c t2= ss of potato & cm 6.20 20.00d 5.55c 301.25d 13.15c t3= hm sown 10 dapp 6.40 23.30c 5.93bc 335.12c 14.20bc t4= cm sown 10 dapp 6.40 23.33c 6.07bc 336.75c 14.50b t5= hm sown 20 6.40 26.00b 6.20b 347.50c 15.50b 0 5 10 15 20 25 30 30-45 45-60 60-75 75-harvest c g r (g m -2 d -1 ) days after planting fig. 7. cgr of potato in potato + maize intercropping ss of potato & hm ss of potato & cm hm sown 10 dapp cm sown 10 dapp hm sown 20 dapp cm sown 20 dapp 0 10 20 30 40 50 30-50 50-70 70-90 90-110 110harvest c g r (g m -2 d -1 ) days after sowing fig. 8. cgr of maize in potato + maize intercropping ss of potato & hm ss of potato & cm hm sown 10 dapp cm sown 10 dapp hm sown 20 dapp cm sown 20 dapp 18 begum et al. dapp t6= cm sown 20 dapp 6.50 26.18b 6.30b 348.75c 15.80b t7= hm sown 30 dapp 6.50 31.55a 8.40a 495.75b 21.50a t8= cm sown 30 dapp 6.70 31.66a 8.45a 495.72b 21.50a t9= hm sown 40 dapp 6.70 32.00a 8.50a 501.10b 21.50a t10= cm sown 40 dapp 6.70 32.66a 8.60a 501.12b 21.60a t11= sole potato 6.70 33.33a 8.80a 535.70a 22.50a level of significance ns 0.01 0.01 0.01 0.01 cv (%) 4.05 3.42 3.61 3.45 4.70 in a column figures having common letter (s) do not differ significantly as per dmrt yield and yield components of maize yield and yield components viz., number of cobs m-2, number of grains cob-1, 1000grain weight and grain yield of maize were influenced significantly under different intercropping (table 2). the maximum cobs m-2 (6.13) was recorded in t12 (sole hybrid maize) which was followed by t1. the lowest number of cobs m -2 (5.33) was recorded in cm sown 40 dapp. there was no significant variation observed when maize was intercropped with potato but it reduced gradually with delayed sown of maize. it might be due to lower number of maize population. in delayed sown maize, germination of maize was affected and seedlings growth was hampered due to heavy shade of potato canopy. as a result, poor growth as well as lower number of cobs m-2 was observed. similar result was observed by zaag and demagante, 1990. number of cobs m-2 of maize was found positively correlated with grain yield (r = 0.94). the highest number of grains cob-1 and 1000-grain weight were observed in sole hybrid maize which was statistically different from all other treatments (table 2). in general, the highest number of grains cob-1 was observed in monoculture due to the plants having more space, light and nutrient in sole cropping (moula et al., 2000). on the other hand, it was decreased in intercropped situation depending upon the sowing times (table 2). number of grains cob-1 gradually reduced with delaying sown of maize. it might be associated with intense competition for growth resources and high temperature at later growth stage (islam, 2002). grain yield of maize almost resembled to its yield contributing characters observed sown at different dates with potato (table 2). the maximum grain yield (11.26 t ha-1) was observed in sole hybrid maize which was statistically at par with hybrid maize simultaneous sowing with potato. it showed that hybrid maize and respective intercrops were higher yielder which might be due to cumulative effect of better yield attributes. on the other hand, composite maize and respective intercrops were lower yielder might be due to poor yield attributes. higher yield of maize was observed in monoculture compared to respective intercropped might be due to no intercrop competition for light, nutrients, moisture and space. yield of maize was gradually decreased with delaying sowing due to hot temperature that shortening the growth period at later stage. ifenkwe and odurukwe (1990) also reported that potato yields increased with delay sowing in association with maize while maize yields decreased as its sowing date was delayed. table 2. grain yield and yield components of maize in potato +maize intercropping as affected by sowing date of maize treatments cobs m-2 (no.) grains cob-1 (no.) 1000-grain wt.(g) grain yield (t ha-1) 19 system productivity of potato + maize intercropping as affected by sowing date t1= ss of potato & hm 5.97a 535.18b 347.53ab 9.43ab t2= ss of potato & cm 5.45c 398.87de 346.90ab 6.00de t3= hm sown 10 dapp 5.92a 500.40bc 342.25b 9.07b t4= cm sown 10 dapp 5.45c 380.91de 340.63b 5.60de t5= hm sown 20 dapp 5.92a 483.53bc 335.50b 8.57bc t6= cm sown 20 dapp 5.40c 371.67e 332.63b 5.36e t7= hm sown 30 dapp 5.87a 470.53bc 327.65b 8.17bc t8= cm sown 30 dapp 5.35c 355.20e 324.72b 5.00e t9= hm sown 40 dapp 5.81ab 450.58cd 320.04b 6.75cde t10= cm sown 40 dapp 5.33c 345.25e 319.15b 4.70e t12= sole hm 6.13a 610.20a 376.77a 11.26a t13= sole cm 5.50bc 500.00bc 350.33ab 7.50bcd level of significance 0.01 0.01 0.01 0.01 cv (%) 2.54 6.82 4.26 12.37 in a column figures having common letter (s) do not differ significantly as per dmrt intercrop efficiency potato equivalent yield (pey) and economic performance of potato + maize intercropping have been presented in table 3. intercrop productivity was evaluated by equivalent yield (bandyopadhyay, 1984). the highest pey (31.30 t ha-1) was observed when hybrid maize sown at 30 dapp. monetary advantage was estimated following shah et al. (1991). the highest gross return (tk. 426925 ha-1), gross margin (tk. 282680 ha-1) and benefit cost ratio (2.79) were observed in the same treatment t7 (hm sown 30 dapp). table 3. equivalent yield and economic performance of the component crops in potato maize intercropping as affected by sowing date of maize treatments potato equivalent yield (t ha-1) gross return (tk. ha-1) cost of cultivation (tk. ha-1) gross margin (tk. ha-1) benefit cost ratio t1 24.47 244700 112322 132378 2.18 t2 20.30 203000 112322 90678 1.81 t3 25.08 250800 112322 138478 2.23 t4 20.92 209200 112322 96878 1.86 t5 25.78 258800 112322 146478 2.30 t6 22.23 222300 112322 109978 1.98 t7 31.30 313000 112322 200678 2.79 t8 27.50 275000 112322 162678 2.45 t9 29.60 296000 112322 183678 2.64 t10 27.24 272400 112322 160078 2.43 t11 22.50 225000 97943 127057 2.30 t12 13.51 135100 62020 73080 2.18 t13 9.00 90000 57690 32310 1.56 market price (tk. kg-1): potato 10, maize 12. conclusion hybrid maize sown 30 days after potato planting was found the most productive and profitable intercropping system for getting higher potato equivalent yield and monetary advantage without affecting the main crop yield. 20 begum et al. references ahmed, f., m. n. islam, m. t. rahman, m. a. jahan and m. s. a. khan. 2010. leaf area index, radiation interception, dry matter production and grain yield of hybrid maize as influenced by plant spacing. bangladesh agron. j. 13(1&2): 51-58. alam, m. z. 2003. influence of planting dates and nitrogen levels on growth, grain yield and nitrogen utilization of barley. phd dissertation, crop physiology laboratory, dept. botany, rajshahi univ., bangladesh. alom, m. s. 2007. performances of different hybrid maize (zea mays l.) varieties under intercropping systems with groundnut (arachis hypogaea l.) and mungbean (vigna radiata l.). phd thesis, dept. of botany, rajshahi univ., rajshahi, bangladesh. akhteruzzaman, m., m. n. islam, b. l. nag and m. t. rahman. 2008. productivity of potato-hybrid maize intercropping under different fertilizer levels. eco-friendly agril. j. 1(5): 300-303. bandyopadhyay, s. n. 1984. nitrogen and water relations in grain sorghum-legume intercropping systems. ph.d. dissertation, indian agril. res. inst., new delhi. barc (bangladesh agricultural research council). 2005. fertilizer recommendation guide. bangladesh agril. res. coun. (barc), farmgate, dhaka-1215. pp.73-99. begum, s., m. n. islam, m. t. rahman, j. a. chowdhury and m. i. haque. 2010. suitability study of different chilli varieties for intercropping with sweet gourd. j. expt. bios. 1(2): 1-4. cimmyt office in bangladesh. 2006. maize whole family training. in: food security in bangladesh: improving wheat, maize and papaya production and impacts of arsenic contamination. project annual report for 2005-2006. pp. 31-44. demagante, a. l. and v. p. zaag. 1988. the response of potato (solanum spp.) to photoperiod and light intensity under high temperatures. potato res. 31: 73-83. gardner, f. p., r. b. pearce and r. l. mitchell (eds.). 1985. growth and development. physiology of crop plants. lowa state univ. press, ames, usa. pp.187-208. ifenkwe, o. p. and s. o. odurukwe. 1990. potato/maize intercropping in the jos plateau of nigeria. field crops res. 25: 73-82. islam, m. n. 2002. competitive interference and productivity in maize-bushbean intercropping system. ph.d. dissertation, dept. agron., bangabandhu sheikh mujibur rahman agril. univ., gazipur, bangladesh. islam, m. n., m. a. hossain, m. s. a. khan, b. l. nag, m. a. i. sarker, m. t. rahman and i. m. ahmed. 2007. fertilizer management in hybrid maizesweet potato intercropping systems. bangladesh j. crop sci. 18(1): 89-94. kephart, k. d., d. r. buxton and s. e. taylor. 1992. growth of c3 and c4 perennial grasses in reduced irradiance. crop sci. 32: 1033-1038. kumar, c. a., s. kumar, g. p. srivastava and s. kumar. 2000. production potential and fertilizer economy in winter maize + potato based intercropping system. orissa j. hort. 28(1): 51-55. kuruppuarachchi, d. s. p. 1990. intercropped potato (solanum spp.): effect of shade on growth and tuber yield in the northwestern recosol belt of sri lanka. field crops res. 25: 61-72. mahfuza, s. n., m. n. islam, a. hannan, m. akhteruzzaman, and s. begum. 2012. intercropping 21 system productivity of potato + maize intercropping as affected by sowing date different vegetables and spices with pointed gourd. j. expt. biosci. 3(1): 77-82. moula, m. g., s. begum, m. a. rahman and m. a. quayyum. 2000. effect of row spacing and nitrogen levels on the yield and yield attributes of maize. bangladesh j. agril. sci. 27: 5-6. santalla, m., p. a. casquero, a.m. de ron. 1999. yield and yield components from intercropping improved bush bean cultivars with maize. agron. crop sci. 183: 263-269. shah, n. h., p. k. koul, b. a. khanday and d. kachrov. 1991. production potential and monetary advantage index of maize intercropped with different grain legumes. indian j. agron. 36(1): 23-28. watiki, j. m., s. fukai, j. a. banda and b. a. keating. 1993. radiation interception and growth of maize/cowpea intercrop as affected by maize plant density and cowpea cultivar. field crops res. 35: 123-133. zaag, v. p. and a .l. demagante. 1990. potato (solanum spp.) in an isohyperthermic environment. v. intercropping with maize. field crops res. 25: 157-170. bangladesh agron. j. 2014, 17(1): 67-72 foliar and soil fertilization effect on seed yield and protein content of soybean m. a. mannan department of agronomy, bangabandhu sheikh mujibur rahman agricultural university, gazipur-1706, bangladesh corresponding author: mannanbsmrau@yahoo.com key words: soybean, yield, protein content, foliar and soil fertilization abstract a field experiment was carried out at agronomy farm of patuakhali science and technology university, dumki, patuakhali, from december 2011 to march 2012, to study the effects of nutrient foliar spray on soybean growth, yield and protein content. soybean variety shohag was used as the test crop. n, npk, npks and npkmg were sprayed and applied in the soil at vegetative and pod filling stages. soil fertilizations were done as recommended dose, and no soil and foliar fertilization were considered as control. plants were sprayed at the rate of 100 mg/l of water corresponding to each nutrient. the experimental design was a split plot with three replications. result indicated that nutrient foliar spray, either singly or in combination, enhanced the growth and yield of the soybean as well as protein content in soybean seed, at the two growth stages compared to soil fertilization. however, spraying nutrients during pod filling stage was better than vegetative spraying stage in all characters studied. the highest amount of protein content in soybean seed and grain yield were obtained by spraying npkmg. introduction soybean (glycine max (l) merr.) belongs to leguminous family ranked as a top oilseed crop, which provides approximately 50% edible oil of the world (akparobi, 2009). it has been recognized as an ancient crop plant since the origin of agriculture (jandong et al., 2011). due to the large amount of macro and micro nutrients, it has been considered as a nutritious food for human needs, livestock, industrial and medicinal purposes (akparobi, 2009). soybean seed consists of 18 to 25% oil and 30 to 50% protein. protein of soybean seed contains amino acids required for human nutrition and livestock (raei et al., 2008). salwa et al. (2011) stated that soybean is a crop that compensates shortage of oil and protein of other crops. furthermore, it is a good source for high energy, protein and essential nutrients to human and animals. a successful initiative to introduce soybean in bangladesh was taken in the beginning of the eighties. at present soybean is not extracted in our country for oil because of lacking industrial facilities and is consumed as food products (soya-milk, soya-meat, soya-flour etc.) and ingredients of animals and poultry feed. usually, more than 95 % of the total population of bangladesh cannot afford protein rich food like fish, meat, egg, milk etc. due to higher price and low production. so, as supplement of low cost protein, soybean should be cultivated in more areas which can help to alleviate protein calorie malnutrition of cereal based diet in bangladesh. for optimum plant growth, nutrients must be balanced or in other words the soil must have nutrients that are needed for plants (chen, 2006). biological n 2 fixation and mineral soil or nitrogen fertilizer are the main source of meeting the nitrogen (n) requirement of high-yielding soybean (salvagiottiet et al., 2008). the mineral nutrition of crops can be supplemented with fertilizer application to soils or foliage (mallarino et al., 2001). fertilization with n, phosphorus (p), potassium (k) and other nutrients can affect yield and many physiological processes, which in turn could influence grain yield and protein concentration (haq and mallarino, 2005). foliar spraying is a new method for crop feeding, which nutrients in form of liquid are used into leaves (nasiri et al., 2010). foliar application of nutrient elements is more beneficial than soil application. since application rates are lesser as compared to soil application, mailto:mannanbsmrau@yahoo.com 68 m. a. mannan and crop reacts to nutrient application immediately (zayed et al., 2011). soybean higher yield and quality as well as its oil could be be obtained by foliar spray of nutrient elements (vahedi, 2011). arif et al. (2006) found that based on soil properties, foliar spraying could be effective 6 to 20 times as compared to soil application. foliar application could be an advantage for crop growth (seifinadergholi et al., 2011). the objective of this study was therefore to assess the effect of foliar nutrient spray singly or in combinations before flowering and pod filling stages, on the growth, yield and seed quality of soybean. materials and methods the field experiment was carried out at agronomy farm of patuakhali science and technology university, dumki, patuakhali, from december 2011 to march 2012 to determine the effects of foliar spray of nutrients on the growth, yield and protein content of soybean seed. before planting, soil samples were collected from experimental area at 0-30 cm depth. the results of soil analysis were shown in table 1. the soybean variety used was shohag. the experimental design was splitplot having 4 m x 2.5 m plot size with three replications. table 1. physical and chemical properties of experimental soil soil properties value soil texture clay silt (%) 28.2 clay (%) 68.5 sand (%) 3.3 organic matter (%) 1.6 ph 6.2 electrical conductivity (ds m-1) 1.45 n (%) 0.66 p (ppm) 5.60 k (ppm) 5.31 zinc (mg kg-1) 1.09 iron (mg kg-1) 2.76 manganese (mg kg-1) 2.00 each block (replicate) was divided into main plots where growth stages (vegetative and pod filling) and six subplots to which nutrients were foliarly applied as exclusively n, npk, npks and npkmg at the rate of 100 mg litre-1 of each nutrient were randomly assigned. soil fertilizations were done as recommended dose and no soil and foliar fertilization in control plot. nitrogen was derived from urea, phosphorus from sodium dihydrogen orthophosphate (na2h 2po 4.2h 2o), potassium from potassium chloride (kcl), sulphur from gypsum (caso 4) and magnesium from hydrated magnesium chloride (mgcl2.6h 2o). planting of seeds was done on 03 december, 2011 maintain spacing 30 cm x 5 cm. weeding was done at 2 and 6 weeks after sowing (was). plants were sprayed at vegetative (4 weeks after sowing) and pod filling (8 weeks after sowing) stages as per treatment. ten selected plants were used to take the data from each plot of each replication. data were recorded for grain yield, plant height, dry weight of different plant parts, number of pods plant-1, number of seeds pod-1 and 100 grain weight. the nitrogen concentration in seeds was measured with micro-kjeldahl method as described by peach and tracey (1956) and the seed protein content was determined by multiplying the nitrogen percentage and protein factor using the formula, protein percentage = nitrogen percentage x 5.71 (breese, 1931). data collected were analyzed using mstatc program. the means differences among the treatments were compared by least significance difference test (lsd). 69 foliar and soil fertilization effect on soybean results and discussion effects of foliar spray on plant height and dry matter production the data presented in table 2 showed that the foliar application of essential mineral nutrients, either singly or in combinations, was consistently beneficial to soybean growth and development. similarly, foliar spray during the vegetative and pod filling stages, also enhanced the performance of soybean. this result agreed with the work of tayo (1981). table 2. effects of foliar spray on plant height and dry matter production of soybean interaction of growth stages and nutrients plant height (cm) number of branches plant-1 stem dry weight (g) leaf dry weight (g) total dry weight (g) v x control 39.92 3.00 9.40 15.51 24.94 v x n 41.05 4.11 10.49 16.47 26.96 v x npk 44.24 5.11 9.86 19.16 29.02 v x npks 44.61 5.33 11.12 20.43 31.55 v x npkmg 46.92 7.38 11.95 21.63 33.58 v x r 43.72 4.35 9.89 16.95 26.84 p x control 41.85 3.67 10.09 18.89 28.98 p x n 42.45 5.00 11.02 20.10 31.12 p x npk 42.97 6.00 12.71 20.95 33.66 p x npks 43.51 7.67 13.59 21.79 35.38 p x npkmg 44.85 8.68 14.97 23.47 38.44 p x r 42.26 5.86 10.51 21.54 32.05 lsd (0.05) 8.29 1.53 2.54 15.50 16.39 cv (%) 10.24 9.49 10.17 12.35 13.37 vvegetative stage, p – pod filling stage, control (no soil and foliar fertilization), nfoliar spray with single n, npkfoliar spray with npk, npks foliar spray with npks, npkmg foliar spray with npkmg, r recommended fertilizer dose (1/2 n and full pk basal dose in soil + ½ n top dressing) plant sprayed with different nutrient combination generally had significantly higher plant height, higher number of branches, leaf dry weight, stem dry weight and total dry weight than control plants. plant spraying with npkmg produced the tallest plant with the highest total dry matter production in both the spraying stages. this could be that mg is important in chlorophyll formation, resulting in higher photosynthesis and higher leaf growth. stimulated photosynthetic activity and synthesis of chloroplast and protein which might have resulted in higher dry matter production as reported in soybean crop (mishra and agrawal, 1994). spraying during the pod filing growth stage led to plants with higher plant height, branches plant-1, stem dry weight, leaf dry weight and total dry weight than that of spraying during vegetative stage. this was probably due to the fact that all plants had reached the peak of vegetative growth before spraying was done. the fact that spraying during the pod filling growth stage would be ultimately better than spraying at vegetative stage, since the former plants had significantly higher values of all the parameter studied. yield attributes and protein of seed number of pods: number of pods plant-1 is an important yield component in soybean and all the foliar spray treatments viz., n, npk, npks and npkmg increased the number of pods plant-1 at both growth stages (table 3). the foliage applied nitrogen and phosphorus at the vegetative stage might have effectively absorbed and translocated to the pods resulting in more number of pods plant-1. the results obtained by solaiappan et al. (2002) in redgram are concomitant to the present finding. foliar spray of these nutrients at pod filling stage of crop growth might have caused efficient translocation of 70 m. a. mannan photosynthates from source to sink. however, sprayed with npkmg during the pod filling stages of growth was higher and significantly different from those plants sprayed during at vegetative stage of growth. the foliar application of nutrients through npkmg at pod filling stage might have reduced flower drops. this might have significantly increased the number of pods plant-1 as reported by ganapaty et al. (2008). number of seed pod-1 and seed index: foliar application of essential nutrients during vegetative and pod filling stages of crop growth significantly influenced the number of seed pod-1 and 100-seed weight (table 3). this might be due to better absorption of nutrients applied through foliage leading to better activity of functional root nodules resulting in more dry matter production. this could have lead to more flower production and subsequently pod formation and other yield attributes. the increased 100-seed weight might be attributed to increased mobilization of metabolites to the reproductive sinks. furthermore, plants sprayed with npkmg during pod filling stage had significantly the highest number of pods plant-1 and 100-seed weight in respect of sprayed at vegetative stage. table 3. effects of foliar spray on yield, yield contributing characters and protein % of soybean interaction of growth stages and nutrients pods number per plant seed number per pod 100-seed weight (g) grain yield m-2 (g) protein (%) v x control 83.67 2.06 4.83 155.10 21.33 v x n 85.70 2.23 6.01 164.34 25.00 v x npk 85.38 2.50 7.92 170.09 30.00 v x npks 87.00 2.60 8.39 171.37 31.10 v x npkmg 90.33 3.00 10.0 182.74 35.67 v x r 84.65 2.33 5.66 169.05 27.45 p x control 85.09 2.30 6.85 148.40 21.00 p x n 86.00 2.56 7.63 165.07 26.00 p x npk 87.67 2.73 8.19 173.75 29.33 p x npks 88.49 2.83 9.24 174.60 33.00 p x npkmg 92.67 3.13 12.52 187.20 37.33 p x r 86.55 2.46 7.03 169.30 27.33 lsd (0.05) 2.01 0.35 2.06 10.47 3.69 cv (%) 1.64 5.93 9.31 3.80 5.09 vvegetative stage, p – pod filling stage, control (no soil and foliar fertilization), nfoliar spray with single n, npkfoliar spray with npk, npks foliar spray with npks, npkmg foliar spray with npkmg, r recommended fertilizer dose (1/2 n and full pk basal dose in soil + ½ n top dressing) grain yield and protein (%) in seed: interaction effects of foliar application of different nutrients and growth stages had significant variations in grain yield and protein content (table 3). plant sprayed with npkmg during vegetative and pod filling stages shown a better performance in grain yield and yield contributing attributes and protein % compared with other treatment combinations. foliar spraying during the pod filling stage was more effective than during vegetative stage in all the parameters studied, probably because nutrients applied during pod filling were readily used for photosynthesis and assimilates quickly mobilized for grain filing and protein accumulation in grain. the increased yield might be due to enhanced yield attributes like number of pods plant-1, number of seeds pod-1, 100-seed weight due to increased uptake of nutrients by soybean by effective translocation of nutrients from sink to reproductive area of crop. spraying with npkmg during pod filling stage enhanced yield and protein content of soybean, compared with other nutrient combinations. this agreed with the work of ashour and thallooth (1983). in conclusion, it appears that nutrient spraying enhanced soybean growth, development, yield and protein content and 71 foliar and soil fertilization effect on soybean spraying in the pod filling stage is better than spraying during vegetative stage. as for the nutrient combinations, npkmg appear to give the highest yield and protein content of soybean. acknowledgement the author is grateful to the faculty of higher studies, patuakhali science and technology university, patuakhali for funding this study. references akparobi, s. o. 2009. evaluation of six cultivars of soybean under the soil of rainforest agro-ecological zones of nigeria. middle-east j. sci. res. 4(1): 06-09. available online at: http://idosi.org/mejsr/mejsr4(1)/2.pdf. arif, m., m. a. chohan, s. ali, r. gul and s. khan. 2006. response of wheat to foliar application of nutrients. j. agric. biol. sci. 1(4). available online at: http://www.arpnjournals.com/jabs/ research_papers/jabs_1106_36.pdf. ashour, n. i. and a. t. thalloth. 1983. effects of soil and foliar application of n during pod development and yield of soybean (glycine max, (l) merill) plants. field crops res. 6: 261-266. breese, j. 1931. factors for converting percentage of nitrogen in foods and feeds into percentages of protein. united statesd.partment of agriculture washington, p.22. chen, j. 2006. the combined use of chemical and organic fertilizer and/or biofertilizer for crop growth and soil fertility. taipei food fert. technol. bull., 17: 1-9. ganapaty, m., g. baradban and n. ramesh. 2008. effect of foliar nutrition on reproductive efficiency and grain yield of rice fallow pulses. legume res. 31: 142-144. haq, m. u. and a. p. mallarino. 2005. respones of soybean grain oil and protein concentrations to foliar and soil fertilization. agron. j. 97: 910918. http://www.academicjournals.org/jmpr/pdf/pdf2010/4sept/nasiri%20 et% 20al.pdf. jandong, e. a, m. i. uguru and b. c. oyiga. 2011. determination of yield stability of seven soybean (glycine max) genotypes across diverse soil ph levels using gge biplot analysis. j. appl. biosci. 43: 29242941. mallarino, a. p., m. u. haq, d. wittry and m. bermudez. 2001. variation in soybean response to early season foliar fertilization among and within fields. agron. j. 93: 1220-1226. available online at: https://www.soils.org/publications/aj/pdfs/93/6/1220. mishra, a. k. and h. p. agarwal. 1994. effect of sulphur on growth, yield, protein and oil content of soybean. j. oilseeds res. 11: 99-102. nasiri y., s. zehtab-salmasi, s. nasrullahzadeh, n. najafi and k. ghassemigolezani. 2010. effects of foliar application of micronutrients (fe and zn) on flower yield and essential oil of chamomile (matricaria chamomilla l.). j. med. plants res. 4(17): 1733-1737. peach k. and m. v. tracey. 1956. modern methods of plant analysis. springer-verlag, berlin. raei. e., m. sedghi and r. sayed sharifi. 2008. effect of bradirizobium inoculation, application of nitrogen and weeding on growth and seed filling rate in soybean. j. agric. technol. 12(43): 91-81. salvagiottiet, f., k. g. cassman, j. e. specht, d. t. walters, a. wiss and a. dobermann. 2008. nitrogen uptake, fixation and response to fertilizer n in soybean: a review. field crop res. 108: 1-13. http://idosi.org/mejsr/mejsr4(1)/2.pdf http://www.arpnjournals.com/jabs/research_papers/jabs_1106_36.pdf http://www.arpnjournals.com/jabs/research_papers/jabs_1106_36.pdf http://www.academicjournals.org/jmpr/pdf/pdf2010/4sept/nasiri https://www.soils.org/publications/aj/pdfs/93/6/1220 72 m. a. mannan salwa, a. i. e., m. b. taha and m. a. m. abdalla. 2011. amendment of soil fertility and augmentation of the quantity and quality of soybean crop by using phosphorus and micronutrients. intl. j. acad. res. 3(2): part 3. available online at: http://www.ijar.lit.az/pdf/10/2011(10-127).pdf. seifinadergholi, m., m. yarnia and f. rahimzade khoei. 2011. effect of zinc and manganese and their application method on yield and yield components of common bean (phaseolus vulgaris l. cv. khomein). middle-east j. sci. res. 8(5): 859-865. solaiappan, d., v. k. paulpandi and n. chellaiah. 2002. effect of graded levels of phosphorus and foliar fertilization on short duration redgram in rainfed vertisol. madras agric. j. 87: 451-454. tayo, t. o. 1981. studies on the effects of foiar spray of nutrients on the performance of cowpea (vigna unguiculata (l) walp). j. agril. sci. camb. cult. sci., cambridge, 96: 375-388. vahedi, a. 2011. the effects of micronutrient application on soybean seed yield and on seed oil and protein content. j. am. sci. 7(6). available online at: http://www.jofamericanscience.org/ journals/amsci/0706/110_5746am0706_672_677.pdf. zayed, b. a., a. k. m. salem and h. m. el sharkawy. 2011. effect of different micronutrient treatments on rice (oryza sativa l.) growth and yield under saline soil conditions. world j. agric. sci. 7(2): 179184. available online at: http://www.idosi.org/wjas/wjas7 (2)/12.pdf. http://www.ijar.lit.az/pdf/10/2011(10-127).pdf http://www.jofamericanscience.org/journals/amsci/ http://www.jofamericanscience.org/journals/amsci/ bangladesh agron. j. 2022, 25(1): 37-45 phenotyping rice germplasm associated with salinity tolerance under hydroponics system a. biswas1*, s. akter1, s. mondal1,2*, h.n. barman1, s. pervin1, m.m.e. ahmed1, m.s. rahman1 and r. yasmeen1 1bangladesh rice research institute, gazipur-1701, bangladesh 2bangabandhu sheikh mujibur rahman agricultural university, gazipur-1706, bangladesh *corresponding e-mail: satyen1981@gmail.com; avijitbrri@gmail.com.com (received: 13 march 2022, accepted: 26 may 2022) keywords: genetic variation, germplasm, phenomics, rice, salinity abstract screening of different rice (oryza sativa l.) germplasms or breeding lines is a continuous effort to identify the promising source. a series of experiments (20) were undertaken to identify promising materials for five years of salinity screening from 2015 to 2019. the materials included total of 3,195 rice germplasm and breeding lines, out of which bangladesh rice research institute (brri) developped 2, 295 germplasms, 193 advanced breeding lines from brri, and 707 advanced breeding lines from international rice research institute (irri), philippines. from this study, the genotypes were categorized as 122 tolerant, 220 moderately tolerant, 1,207 sensetive, and 1,646 highly sensetive. among the brri germplasms, most of the materials (61%) had sensitive responses against salinity, while only 2 and 3% of rice germplasm exhibited tolerant and moderately tolerant, respectively. brri lines comprised 44% sensetive and 35% highly sensetive rice genotypes. in the tolerance level, 4% appeared as tolerant and 17% moderately tolerant against salinity. likewise, irri lines also showed relatively higher tolerance (9%) than the brri germplasm and lines. they were classified into 9 % tolerant and 16 % moderately tolerant rice genotypes. introduction among abiotic stresses, salinity is the second most destructive constraint on rice production after drought, affecting approximately 1 billion hectares of land worldwide (fageria et al., 2012). rice is relatively more sensetive to salt stress in seedling and early vegetative stages (lutts et al., 1995; mondal et al., 2020) and later at the reproductive phage (singh et al., 2010). sodium chloride (nacl) is dominant in saline soils among many salt contaminants and is readily soluble in water to yield toxic ions like sodium (na+) and chloride (cl–). roots of higher plants absorb readily smaller molecule, na+, and ultimately translocate to all plant parts causeingionic imblance, osmotic stress, and nutritional imbalance in rice plants (siringam et al., 2011; barua et al., 2015). direct salt accumulation disrupts metabolic processes and all major morpho-physiological and yield-related features, including tiller number, panicle length, spikelet number per panicle (khatun et al., 1995), grain filling (rao et al., 2013), plant biomass (zeng et al., 2007), and photosynthesis (baker, 2008), resulting drastically yield reduction. an essential tool for managing the rice field's salinity problem is integrating plant tolerance and cultural practices. therefore, development of salt-tolerant high-yielding rice genotypes can be the best attempt to cultivate salinity-affected areas (hakim et al., 2014). rice landraces play a prominent role in attaining local food security and serve as an excellent genetic reserve for rice genomics upgrading (tang et al., 2002). screening of rice germplasm for salt tolerance at the early seedling stage relies on genetic potentiality and seedling vigor under salinity stress. to widen the genetic base, the reliable use of the best sources, identifying a larger number of genotypes mailto:satyen1981@gmail.com mailto:avijitbrri@gmail.com.com 38 biswas et al. under salt stress is necessary. thus, the screening program was undertaken to determine performances of different rice germplasm and advanced breeding lines of both brri and irri against salt stress that can be used as donors in the salinity tolerance breeding program. materials and methods plant materials seeds of rice genotypes were received from plant breeding division, genetic resource and seed division, biotechnology division and hybrid rice division, brri, bangladesh and irri, philippines. an initial evaluation of 3,258 rice genotypes consisting of 2295 bangladeshi germplasm (mostly old indigenous genotypes), 193 advanced breeding lines developed by brri, 707 advanced breeding lines introduced from irri and 62 line/variety from other sources was conducted. beside, pokkali, nona bokra andir 58443-6b-10-3 were used as tolerant check variety and ir29 and irri 154 were used as salt-sensitive check varieties. experimental condition the experiment was done at the greenhouse of the plant physiology division, brri from 2015 to 2019. all the rice germplasms were screened at the seedling stage for salt tolerance in the hydroponics system using irri standard protocol (gregorio et al., 1997). at first, seedlings were raised in the hydroponic system using yoshida nutrients solution with ec level 12 dsm-1 under the laboratory conditions. yoshida nutrient solution comprised macronutrients and micronutrients and was prepared as suggested by yoshida et al. (1976). fig. 1. rapid screening technique for rice genotypes under salinity stress in hydrophonic systems using plastic trays (1= styrofoam ready for seed sowing, 2 = seed sowing, 3 = seedling growing in saline water 4 = experiment is ready for salinity scoring). the screening of rice genotypes for salt tolerance at the seedling stage was conducted in the hydroponics system (gregorio et al., 1997), which is termed as a rapid screening technique that uses plastic trays with tight-fitting thermocol support platform with holes for placing the seeds (figure 1). seeds were sown in the nylon mesh set just below the thermocol platform. before the greenhouse experiment, the seeds were disinfected with naocl solution (200 ml nacl in 1-litre water) and incubated for 48 hours to enhance germination. one pre-germinated seed was sown in each hole of phenotyping rice germplasm associated with salinity tolerance under hydroponics system 39 styrofoam seedling float and the seedling floats were then covered with a lid for 2 to 3 days to promote germination in the dark. the tap water was replaced with yoshida nutrient solution after three days of seeding. salinization was done seven days after sowing. after seven days, salinity was developed by adding crude salt to obtain an ec of 12 dsm-1. the yoshida solution's volume was adjusted to touching the seedling float at two days intervals. the ph was adjusted to 5 and ec was also adjusted with 12 dsm-1 synchronizing with the yoshida solution. when ec was higher than 12 ds m-1, tap water was applied to the solution, and nacl was added when ec was lower than 12 ds m-1. alikely, 1 n hcl was added to the solution when it’s ph was more than 5.0 and 1 n naoh was added when ph was less than 5.0. scoring of rice germplasms and breeding lines based on the visual symptoms like reduced leaf area, changing of lower leaves into whitish color, leaf tip death and leaf rolling, the rice seedlings were categorized as highly tolerant, tolerant, moderately tolerant, sensetive and highly sensetive (table 1). the standard saline tolerant genotypes, pokkali, nona bokra, ir 58443-6b-10-3 and saline sensetive genotype ir29 and irri 154 were used for test comparison. plants were exposed to salinity until the sesetive check variety died. after that rice genotypes were compared with both sesetive and tolerant check variety. if the phenotypes of any plants close to tolerant check variety were identified and the tested genotype as tolerant genotypes close to sensetive check variety e identified the tested genotype as sensetive genotype. the visual scoring for salinity tolerance was done by standard evaluation system (ses) score developed by gregorio et al. (1997). experimental design and analysis experimentals were crried out by following rcbd design with three replications. data analyses were performed using statistical tool for agricultural research (star), version 2.0.1, developed by international rice research institute (star, 2013). table 1. modified standard evaluation score (ses) of visual salt injury at seedling stage (gregorio et al., 1997) score observation tolerance 1 normal growth, no leaf symptoms highly tolerant 3 nearly normal growth, but leaf tips or few leaves whitish and rolled tolerant 5 growth severely retarded; most leaves rolled; only a few are elongating moderately tolerant 7 complete cessation of growth; most leaves dry; some plants drying sensetive 9 almost all plants dead or dying highly sensetive results a total of 3,195 rice germplasms were screened during five-years-period, 2015–2019 (table 2). out of these, 2,295 sources, germplasm were collected from genetic resources and seed division, brri, 193 advanced lines from the plant breeding division, brri and 707 advanced lines from the irri. the response of the rice varieties against salinity is presented in table 2. table 2. the number of rice genotypes rated for salinity tolerance in brri, gazipur, bangladesh from 2015-2019 sources response to salinity total t mt s hs brri germplasm 48 72 774 1,401 2,295 40 biswas et al. brri lines 8 33 84 68 193 irri lines 66 115 349 177 707 total 122 220 1,207 1,646 3195 t = tolerant; mt= moderately tolerant; s = sensetive; hs = highly sensetive from the above study, 125 tolerant, 225 moderately tolerant and 1,245 sensetive and 1,662 highly sensetive germplasms were identified from four different rice grmplasmsources. of the 2,295 genotypes of brri germplasm, 1401 were highly sensetive, and only 48 entries were tolerant to salinity stress (table 2). in brri lines, the higher number of rice genotypes (84) was sensetive, and only eight entries were found tolerant to salinity from a total of 193 advanced breeding lines. similarly, 349 rice genotypes were scored as sensitive and 66 genotypes exhibited tolerance to salinity from 707 advanced breeding lines developed in irri. the percentage of tolerant, moderately tolerant, sensetive, and highly sensitive rice genotypes varied greatly among three different sources of rice genotypes, including brri germplasm, brri lines, irri lines, and others (figure 2). fig. 2. percentage shared by each source of rice genotype groups, including brri germplasm (n=2295), brri lines (n=193), irri lines (n=707). most of the brri germplasms are 40 ensitive (34%) and highly sensitive (61%) to salinity stress and only 2 and 3% of genotypes were tolerant and moderately tolerant, respectively. on the other hand, brri developed advanced breeding lines comprised of 44% 40 ensitive and 35% highly 40 ensitive. in terms of tolerance, 4% appeared as tolerant, and 17% moderately tolerant against salinity stress. like brri germplasm and brri lines, irri lines also had a higher percentage of sensitive (50%) materials. but irri lines had relatively higher tolerance with a figure of 9% tolerant and 16% moderately tolerant rice genotypes. taking into accounts, brri lines and irri lines had higher cumulative frequency of tolerant genotypes ranging from 21 to 25% tolerant and moderately tolerant rice genotypes. the potentiality of different sources of rice genotypes against salinity stress in the present study, screened 3,195 rice genotypes for salinity tolerance. in each group of genotypessources, most of the materials were found sensetive to salinity stress with very few tolerant genotypes. out of 2,295 germplasms, only 48 rice genotypes scored three (3) based on the performance against salinity stress in greenhouse conditions (table 3). table 3. list of 48 rice genotypes from brri germplasm with ses score 3 evaluated during 2015 to 2019 at brri, gazipur, bangladesh name of the genotypes ses hashakumira, bhobanibhog, bhawalia, kumari amon, kolom, lal kumari, pura binni, 3 phenotyping rice germplasm associated with salinity tolerance under hydroponics system 41 kajal kori, binni, khama rang, temboro, lembur, chan moni, murali (2), beti balam, patnai (3), lati sail, nedukenari, raja morol, kajol gouri, jamrishaity, ausbaku, kachra boron, modu sail, binna chupi, ful kumari, raja sail tapl -14, radha, gutiswana, fazla (nawgan), kajal (nawgon), dudkalam, sadamota, lamba vojon, kali binni, kalobirun, boainchabiruim, moinamoti, boleshwas, bambudhan, changaidhan, kalo sail, gaindha, hijoldhiga, munsur, nona khorchi, hoglapata, benapol(brown) from a total of 193 brri lines developed at brri, only eight advanced breeding lines rated score(ses) three (3) based on screening results against salinity stress in greenhouse conditions (table 4). among the tested genotypes, most of them were sister lines and originated from the same crosses. table 4. list of 8 rice genotypes from brri lines with ses score 3 in evaluations conducted from 2015 to 2019 name of the genotypes ses br7091-4r-1, br7098-4r-2, br7100-r-6-6, br7102-4r-1, br7105-4r-2, br71095r-4, br7113-4r-1, br9539-b-12-11-13 3 like brri lines, irri lines also showed potentiality with a better performance against salinity stress. sixty-six advanced breeding lines ranked score (ses) three (3) based on screening results against salinity stress in greenhouse conditions from a total of 707 irri lines produced at irri, philippines (table 5). table 5. list of 66 rice genotypes from irri lines with ses score 3 conducted during 2015 to 2019 at brri, gazipur, bangladesh name of the genotypes source ir15t1409, ir15t1473, ir90477-74-1-2-3, ir106469-23-3-ajy1-b-1, ir108174-bcmu 10-1-b-1, ir126952-1699-41-8-10-9, ir126952-28-55-9-3-15-b, ir126952-2912-508-10-5, ir126952-29-27-58-1-2, ir126952-29-85-275-20-1, ir66946-3r-178-1-1, ir89330-14-3-12-2-3, ir89331-32-3-1-3-2-2, ir90477-74-1-2-3-2-ajy, ir91669-16-32-2-2, ir92860-33-cmu 1-1cmu 2-ajy b, ir09t484, ir87916-4-1-2-1-1-b, ir87938-1-1-1-2-1-3-b, ir87938-1-1-3-2-1-b, ir87938-1-2-2-1-3-b, ir87938-1-2-2-21-b, ir15t1324, ir15t1408, ir15t142, ir15t1466, ir58443-6b-10-3, ir63307-4b-43, ir65833-4b-17-1-3, ir66946-3r-178-1-1, ir69992-ac2, ir69997-ac2, ir70870-bp-25-2, ir72579-b-3-2-3-14, ir72579-b-3-2-3-8, ir72593-b-13-3-3-1, ir72593-b-182-2-2, ir72593-b-3-2-2-2, ir77674-5-1, ir83416-7-b-12-3-1-3-ajyi-b, ir87831-3-11-2-2-bayb, ir87870-6-1-1-1-1-b, ir87872-7-1-1-2-1-b, ir87888-3-ajyi-b, ir14t106, ir15t1074, ir15t1106, ir15t1107 3 discussion in rice, significant genetic diversity in salt stress tolerance is available. combining superior alleles from various sites, the availability of multiple breeding tolerance sources and gene exploration can further extend the genetic base and increase the degree of tolerance (rahman et al., 2016). identified 48 new potential donors for salt tolerance. these new sources show similar tolerance to the previously identified donors commonly used pokkali group and nona bokra. these landraces are currently being cultivated by farmers in the salt-affected areas of the coastal region of south bangladesh and west bengal,india despite their poor grain quality and lower yield. they could also be useful for varietal improvement with conventional breeding tools and new qtls/genes sources for molecular breeding. in the present study, screened 3,195 rice germplasms for salinity tolerance, and most of the materials were collected from the brri germplasm center. in each group of germplasms sources, the majority of the materials were found sensetive to salinity stress. rice has been grouped as a salt-sensitive cereal, especially at its early stage (lutts et al., 1995). from a total of 2,295 germplasm materials, only 120 42 biswas et al. rice genotypes scored (ses) 3 to 5 based on performance against salinity stress in greenhouse conditions with very few tolerant genotypes. in addition to characterizing physiological responses to salt stress, advances have been made in identifying quantitative trait loci (qtls) and genes controlling salinity tolerance traits. for example, several qtls for salt tolerance have been identified in rice, including a major locus on chromosome 1, comprising the major locus saltol obtained from pokkali (bonilla et al., 2002) and skc1 (oshkt1;5) from nona bokra. the saltol locus is involved in na/k homeostasis under salt stress (platten et al., 2013). these qtls improve the salinity tolerance of modern high-yielding varieties (hyv) but do not provide complete tolerance in modern hyv background. thomson et al. (2010) conducted experiment to identify and combine genes and qtls controlling different physiological mechanisms at both the seedling and reproductive stages to rapidly develop rice varieties that can produce higher and more stable yields under high salt stress conditions. further, identified other salinity tolerant genesfrom different sources. by pyramiding, these genes may provide more salinity tolerance in hyv background. it is reported that, seven landraces viz., akundi, ashfal, capsule, chikirampatnai, jataibalam, kalarata and kutipatnai had accumulated less na and comparatively more k, retaining a lower na/k ratio in the leaves (rahman et al., 2016). they essentially restrict the transport of sodium to the shoot. along with rice germplasm screening, also screened advanced breeding lines developed in salinity tolerance breeding programs both from brri and irri. to develop high-yielding salt-tolerant varieties, screened a total of 193 brri lines developed at brri. only 41 advanced breeding lines scored (ses) 3 to 5 based on screening results against salinity stress in greenhouse conditions. among them, most of them were sister lines and originated from the same cross. among tested brri lines, some good breeding lines were promoted as salt-tolerant rice varieties. based on better performance and higher grain yield in actual salinity areas, the advanced breeding lines br5999-82-3-2-hr1, br7105-4r-2, and br7100-r-6-6 were released as brri dhan54, brri dhan61, and brri dhan67, respectively from brri. brri dhan67 can tolerate 8 ds m-1 salinity (brri, 2018) with grain yield of 6.2 t ha-1 yield at south bangladesh under high salinity regime. brri researchers has developed a high-yielding salt-tolerant variety csr23 (also called as iet13769), which can tolerate ph 2.0±10.0 and salinity up to 8 ds m-1(singh et al., 2006). csr23 is better in k+ uptake and na+ exclusion and suitable for the majority of coastal regions. like brri lines, irri lines also showed relatively more potentiality with a better performance against salinity stress. one hundred and eighty-one advanced breeding lines ses score ranked 3 to 5 based on screening results against salinity stress in greenhouse conditions from a total of 707 irri lines produced at irri. recently, a salt-tolerant transgenic line from ir64 variety with overexpressing pcino1 from halophytic wild rice called porteresia coarctata has been developed. p. coarctata is a landrace in india, sri lanka, bangladesh and myanmar. transgenic rice tolerates upto 200 mmoll-1 salt or higher concentration in pots by inositol production under saline conditions and shows normal growth and grain yield under greenhouse conditions (mukherjee et al., 2019). among the promising irri developed breeding lines, ir63307-4b-4-3 and ir78761-b-satb1-28-3-26 were released as brri dhan47 and brri dhan73. the ideal salinity tolerant variety should possess tolerance to the high amount of na+, control the uptake of na+ and keep high uptake of k+, good initial vigor, agronomically superior with high yield potential. before the yield trial, these breeding lines were subjected to screening against salinity in greenhouse conditions and they exhibited a score (ses) 3 during the screening period. these results suggested that the screening results effectively identify promising materials from a large set of accessions. salinity tolerance is a complex trait in rice and controlled by polygenes. as a whole, the identified tolerant rice genotypes from three different sources might have potentiality in developing advanced breeding lines with improved salinity tolerance in rice. pokkali and nona-bokra and their derived lines have been widely used as saline tolerant donors in developing saline tolerant rice varieties and identifying candidate genes against salinity (rahman et al., 2016). recent advances in genomics also suggested the javascript:; phenotyping rice germplasm associated with salinity tolerance under hydroponics system 43 use of diverse parents in developing elite lines from germplasm. moreover, this study's identified materials may serve as a key founder in producing breeding lines with improved salinity tolerance. conclusion screening and identification of new tolerant breeding lines is a continuous work. in the present study, extensive scale screening of rice seedlings was performed against major abiotic stress, salinityto identify promising genetic materials and sources. however, much effort is required to develop tolerance breeding lines across the whole life cycle specially in reproductive stage. in the future, promising materials from the identified set may be tested in both the seedling and reproductive stages. acknowledgment this research received no external funding. we would like to acknowledge necessary support and seed suply provided by the plant breeding division and genetic resources and seed division, bangladesh rice research institute. references baker, n.r. 2008. chlorophyll fluorescence: a probe of photosyn thesis in vivo. ann. rev. plant biol. 59: 89–113. bangladesh bureau of statistics (bbs). 2016. yearbook of agricultural statistics 2015, ministry of planning. government of the people's republic of bangladesh. pp.49-58. bangladesh rice research institute (brri). 2018. adhunik dhaner chas. 21st edition. brri, bangladesh. pp.58-62. barua, r., m. de ocampo, j. egdane, a. m. ismail, and mondal, s. 2015. phenotyping rice (oryza sativa l.) genotypes for physiological traits associated with tolerance of salinity at seedling stage. sci agric. 12: 156-162. bonilla, p., j. dvorak, d. mackill, k. deal and g. gregorio. 2002. rlfp and sslp mapping of salinity tolerance genes in chromosome 1 of rice (oryza sativa l.) using recombinant inbred lines. philippines agric. sci. 85: 68–76. fageria, n.k., l.f. stone and a.b. santos. 2012. breeding for salinity tolerance. in: r fritsche-neto, a borém (eds) plant breeding for abiotic stress tolerance. springer-verlag berlin: heidelberg, pp.103–122. gregorio, g.b., d. senadhira and r.d. mendoza. 1997. screening rice for salinity tolerance, irrl discussion paper series no. 22. hakim, m.a., a.s. juraimi, m.m. hanaf, m.r. ismail, a. selamat, m.y. rafii and m.a. latif. 2014. biochemical and anatomical changes and yield deduction in rice (oryza sativa l.) under varied salinity regimes, biomed res. intl. article id 208584, https://doi.org /10.1155/ 2014/ 208584res. khatun, s., c.a. rizzo and t.j. flowers. 1995. genotypic variation in the effect of salinity on fertility in rice. plant soil. 173: 239–250. lutts, s., j.m. kinet and j. bouharmont. 1995. changes in plant response to nacl during development of rice (oryza sativa l.) varieties differing in salinity resistance. j. exp. bot. 46(12): 1843–1852. mondal, s., j. hasan, p. l. biswas, e. ahmed, t. halder, m. p. ali, a. khatun, m. nasim, t. islam, e. s. ella and e. m. septiningsih. 2020. nitrogen use efficiency in rice under abiotic stress: plant breeding approach", in recent advances in rice research. london, united kingdom: intechopen, doi: 10.5772/intechopen.94038. 44 biswas et al. mukherjee, r., a. mukherjee, s. bandyopadhyay, s. mukherjee, s. sengupta, s. ray and a.l. majumder. 2019. selective manipulation of the inositol metabolic pathway for induction of salt tolerance in indica rice variety. sci. rep. 9(1): 5358. doi: 10.1038/s41598-019-41809-7. platten, j.d., j.a. egdane and a.m. ismail. 2013. salinity tolerance, na+ exclusion and allele mining of hkt1; 5 in oryza sativa and o. glaberrima: many sources, many genes, one mechanism? bmc plant biol. 13: 32. rahman, m.a., m.j. thomson, m. shah-e-alam, m. de ocampo, j. egdane and a.m. ismail. 2016. exploring novel genetic sources of salinity tolerance in rice through molecular and physiological characterization. ann. bot.117(6): 1083-97. rao, p.s., b. mishra and s.r. gupta. 2013. effects of soil salinity and alkalinity on grain quality of tolerant, semi-tolerant and sensitive rice genotypes. rice sci. 20: 284 –291. singh, r.k., b. mishraand g.b. gregorio. 2006. csr23: a new salt tolerant rice variety for india. int. rice res. notes, 31(1): 16-18. singh, r.k., e.d. redoña and l. refuerzo. 2010. varietal improvement for abiotic stress tolerance in crop plants: special reference to salinity in rice. in: pareek, a., s.k. sopory, h.j. bohnertandgovindjee, editors.abiotic stress adaptation in plants. springer, dordrecht, pp.387–415. siringam, k., n. juntawong, s. cha-um, and c. kirdmanee. 2011. salt stress induced ion accumulation, ion homeostasis, membrane injury and sugar contents in salt-sensitive rice (oryza sativa l. spp. indica) roots under iso-osmotic conditions. afr. j. biotechnol. 10: 1340–1346. tang, s.x., y.z. jiang, x.h. wei, z.c. li and h.y. yu. 2002. genetic diversity of isozymes of cultivated rice in china. acta agron. sin. 28: 203–207. tang, t., j. lu and j. huang. 2006. genomic variation in rice: genesis of highly polymorphic linkage blocks during domestication. plos genet. 2: 1824–1833. thomson, m.j., m. de ocampo, j. egdane. 2010. characterizing the saltol quantitative trait locus for salinity tolerance in rice. rice 3: 148–160. zeng, y., h.z. zhang, l. shen, s.j. sun, m. wang, d. liao, x. liu, x. wang, f. xiao and g. wen. 2007. evaluation of genetic diversity of rice landraces (oryza sativa l.) in yunnan, china. breed. sci. 57: 91–99. impacts of environmental change and management practices on phonological events and yield of mustard at different sowing dates bangladesh agron. j. 2015, 18(2): 45-52 impact of sowing date induced temperature and management practices on development events and yield of mustard m.s.a. khan and m.a. aziz agronomy division, bangladesh agricultural research institute, joydebpur, gazipur-1701, bangladesh corresponding author: shawquatshahadat@yahoo.com key words: brassica spp., temperature, growing degree days, productivity abstract the experiment was conducted at the research field of the agronomy division, bangladesh agricultural research institute (bari), joydebpur, gazipur, during rabi season of 2014-2015 to find out the relationship between different development events of mustard crop and sowing dates induced temperature as well as to minimize the yield reduction of the crop by adopting appropriate management practices. the mustard var. bari sarisha-15 was sown on 06, 25 november and 14 december 2014. crop accumulated lower growing degree days (gdd) i.e., 72.15, 521.10 and 1070 to 1154 °c were observed for the events of emergence, 50 % flowering and maturity on 14 december sowing. late sown plants took minimum time from flowering to maturity (36 days) due to increased temperature and high variability in both maximum and minimum temperature. the highest seed yield (1569 kg ha-1) was recorded from 06 november sowing with high management practices while the lowest seed yield (435 kg ha-1) from 14 december sowing with low management practices. at high management practices the crop yielded 1183 kg ha-1 at 14 december sowing. yield reduction at late sowing condition was reduced to some extent with high management practices. the seed yield reductions at 14 december sowing as compared to high management practices at 06 november sowing were 72, 43 and 25% under low, medium and high management, respectively. introduction agriculture is one of the most vulnerable sectors to the climate change impact in bangladesh. climate change refers to any change in climate over time, whether due to natural variability or as a result of human activity (ipcc, 2007). ipcc reported that the area averaged annual mean warming will be around 3°c in the decade of 2050s and around 5°c in the decade of 2080s over land part of asiatic region. this change may alter the geographical distribution and growing season of agricultural crops (porter, 2005). among the different climatic factors temperature adversely affects crops especially winter crops in bangladesh. mustard is one of the major oil seed crops in bangladesh. its grows in temperature between 10°c and 30°c, but the optimum temperature for growth of brassica napus and brassica rapa species is about 20°c (thomas, 1984). in bangladesh, it is grown under different environmental situations such as timely or late sown, with or without fertilizer and rainfed or irrigated conditions. it is mostly grown after t. aman rice in rice based cropping pattern. since, mustard is grown in winter season and winter is becoming shorter due to climate change, the growth of the crop may be affected by the climate change . high temperature in brassica enhanced plant development and caused flower abortion with significant loss in seed yield (rao et al., 1992). most of the cultivated soils have growth limiting problems associated with mineral-nutrient deficiencies (cakmak, 2002). nitrogen fertilization has been reported to mitigate the adverse effects of abiotic stress (waraich et al., 2011). on the other hand potassium plays a crucial role in survival of crop plants under 46 khan et al. environmental stress conditions (munns, 2005). however, it is necessary to determine the relationship between different development events of the crop and the prevailing temperature for the development of appropriate management option to minimize the yield reduction. therefore, this study was done to analyze the impacts of sowing date induced temperature and management practices on development events and yield of mustard. materials and methods the experiment was conducted at the research field of the agronomy division, bangladesh agricultural research institute (bari), joydebpur, gazipur, during rabi season of 20142015. the location of the experimental site is situated at about 230 59´ north latitude, 900 24´ east longitudes and an altitude of 8.4 m above sea level. the soil was silty clay in texture with ph of 6.5. the experiment was laid out in a split-plot design with three replications. the sowing dates were: i. 06 november (timely), ii. 25 november (late) and iii. 14 december (too late); while the management practices were: i. low: 60-15-30-10 kg npks/ha, no irrigation, no weeding, no pesticide. ii. medium: 80-25-60-20 kg npks/ha, one weeding at 21 dae, two irrigations at rosset and flowering stages & spraying pesticides, and iii. high: 120-35-90-30 kg npks/ha, one weeding at 21 dae, two irrigations at rosset and flowering stages, & spraying pesticides. the sowing dates were assigned in the main plots and management practices in sub-plots. the mustard var. bari sarisha-15 was used as a test crop. seeds were sown in lines with maintaining 30 cm row to row spacing. half of urea and full doses of other fertilizers were applied at the time of final land preparation. the remaining half of urea was top dressed at vegetative and flowering stage followed by irrigation. in case of low management, all fertilizers were applied at the time of final land preparation. insecticide and fungicide were sprayed in the respective treatment plots. admire 200sl @ 1 ml/liter of water was sprayed at 20 and 35 dae to control jassids and white flies. rovral-50 wp @ 2 g/liter of water was sprayed at 30 and 45 dae to control alternaria diseases. daily temperatures were recorded for computing required growing degree days (gdd) for different stages. gdd were computed by using daily normal maximum air temperature, minimum air temperature, mean air temperature and considering base temperature of 5º c for mustard (singh et al., 2014). the sum of degree days for the completion of different development stage of mustard were obtained by using the following formula (kumar et al., 2008); accumulated gdd (º c day) = summation (daily mean air temperature in º c – base temperature of mustard). at flowering stage, plant samples were collected from an area of one square meter of all treatments and different plant parts of the collected samples were separated and then oven dried at 70 ºc for 4 days to measure the dry weight. at harvest, yield contributing characters were recorded from selected five plants and yield data were recorded by harvesting one square meter area. data were analyzed by mstat-c and means were compared using least significant difference (lsd). results and discussion days for development events total number of days required for different development events of mustard grown under different sowing dates and management practices are presented in table 1. all developmental events varied due to variations in sowing dates and management practices. the events of emergence, first flowering and 50% flowering did not differ by management practices but differed by sowing dates. the crop sowm on 25 november took maximum days (6) for emergence and the minimum days (4 days) on 06 november 2014 december sowing took maximum days (34 ) for first flowering and 50% flowering (38 days), whereas crop 47 impact of sowing date induced temperature and management sown on 06 november took minimum days (29) for first flowering and 50% flowering (35 days). the days for maturity varied by sowing date and management practices. sown on 06 november took maximum days (80 to 83), while that of 14 december took the minimum days for maturity (74 to 78). crop with low management practices took minimum days for maturity while medium and high management practices took maximum days. the minimum day (74) for maturity was found in plants of 14 december sowing at low management practices. plants developed from both the medium and high management practices took similar days for maturity at each sowing date. table 1. total number of days required for different developmental events of mustard grown at different sowing dates under different management practices treatments developmental events sowing dates management emergence first flowering 50% flowering maturity low 4 29 35 80 medium 4 29 35 83 06 nov. high 4 29 35 83 low 6 33 39 79 medium 6 33 39 83 25 nov. high 6 33 39 83 low 5 34 38 74 medium 5 34 38 78 14 dec. high 5 34 38 78 temperatures and development events both maximum and minimum temperatures were higher at 06 november sowing that reduced the number of days for emergence and first flowering (table 2). the higher maximum temperatures for emergence and flowering were 33.0 ± 0.94 °c and 29.0 ± 1.80 °c and minimum were 21.9 ± 2.35 °c and 16.1 ± 2.20 °c, respectively. table 2. prevailing temperature during different development events of mustard grown at different sowing dates under different management practices during rabi season, 2014-2015 maximum temperature (°c) minimum temperature (°c)developmental events sowing dates range mean ± sd range mean ± sd 06 november 32.2 34.0 33.0 ± 0.94 19.5 25.0 21.9 ± 2.35 25 november 26.5 28.8 27.5 ± 0.72 13.6 15.0 14.3 ± 0.57 sowing to emergence 14 december 20.7 27.8 24.4 ± 2.82 13.0 17.0 14.5 ± 2.06 06 november 26.5 34.0 29.0 ± 1.80 13.6 21.2 16.1 ± 2.20 25 november 15.6 28.8 24.5 ± 3.54 11.0 17.0 13.7 ± 1.94 emergence to first flowering 14 december 15.6 30.0 24.8 ± 3.26 9.8 19.7 13.0 ± 3.07 06 november 22.3 28.8 24.9 ± 2.98 12.5 17.0 15.0 ± 1.96 25 november 21.2 29.4 24.5 ± 2.45 11.0 19.2 12.1 ± 1.99 first flowering to 50% flowering 14 december 15.5 26.7 19.4 ± 5.09 12.0 15.3 13.0 ± 1.54 06 november 15.5 30.0 24.3 ± 3.52 9.8 19.7 13.2 ± 2.65 25 november 15.5 30.0 29.6 ± 2.39 9.8 19.7 15.7 ± 3.05 50 % flowering to maturity 14 december 20.5 33.0 27.6 ± 2.45 10.0 21.0 14.1 ± 3.28 due to high variability in maximum temperature (range: 15.5 – 26.7 °c, mean: 19.4 ± 5.09 °c) 14 december sowing took minimum days from first flowering to 50 % flowering. from 50% flowering to maturity, temperatures were lower at 06 november sowing (max.) that increased the number of days for maturity. average maximum and minimum temperatures for 50% flowering to maturity were higher in 25 november sowing than 14 december 48 khan et al. sowing. the maximum and minimum temperatures ranged from 15.5 – 30.0 °c and 9.8 – 19.7 °c for 25 november sowing and 20.5 – 33.0 °c and 10.0 – 21.0 °c 14 december sowing, respectively. the high variability in both maximum and minimum temperature induced by 14 december sowing enhanced maturity of the mustard crop (fig. 1). 0 5 10 15 20 25 30 35 1 4 3 3 5 1 4 3 3 9 1 4 3 4 3 1 4 3 4 7 1 4 3 5 1 1 4 3 5 5 1 4 3 5 9 1 4 3 6 3 1 5 0 0 1 1 5 0 0 5 1 5 0 0 9 1 5 0 1 3 1 5 0 1 7 1 5 0 2 1 1 5 0 2 5 1 5 0 2 9 1 5 0 3 3 1 5 0 3 7 1 5 0 4 1 1 5 0 4 5 1 5 0 4 9 1 5 0 5 3 1 5 0 5 7 t em p er at u re ( °c ) julian days min max flowering 14343 14362 15016 09 dec 28 dec 17 jan fig. 1. prevailing temperature from flowering to maturity of mustard grown at different sowing dates (arrows indicate starting of flowering for different sowing dates). growing degree days for development events the accumulated growing degree days (gdd) required for different development events of mustard varied under different sowing dates and management practices (table 3). among the different dates of sowing, 06 november sowing accumulated maximum gdd of 89.70, 591.35 and 665.25 °c for the events of emergence, first flowering and 50% flowering, respectively. the minimum accumulated gdd of 72.15 and 521.10 °c were observed for the events of emergence and 50% flowering at 14 december sowing, respectively. for maturity stage of the mustard plants, the maximum accumulated gdd (1284.35 to 1323.65°c) was recorded on 06 november sowing and the minimum (1070.20 to 1154.20°c) on 14 december sowing. the gdd also varied under different management practices of mustard at maturity. the minimum gdd was observed for maturity under low management practices at all dates of sowing. total dry matter total dry matter production at flowering and their distribution in different plant parts under different sowing dates and management practices (fig. 2). the highest total dry matter (93 g m-2) was recorded in plants of 06 november sowing with high management, which was identical with medium management practices at the same date of sowing. the lowest total dry matter (9 g m-2) was recorded at 14 december sowing with low management practices. table 3. accumulated growing degree days (°c) for different developmental events of mustard grown at different sowing dates under different management during rabi season, 2014-2015 treatments developmental events sowing dates management emergence first flowering 50% flowering maturity 49 impact of sowing date induced temperature and management low 89.70 591.35 665.25 1284.35 medium 89.70 591.35 665.25 1323.65 06 nov. high 89.70 591.35 665.25 1323.65 low 95.45 475.45 564.50 1115.90 medium 95.45 475.45 564.50 1172.55 25 nov. high 95.45 475.45 564.50 1172.55 low 72.15 476.3 521.10 1070.20 medium 72.15 476.3 521.10 1154.20 14 dec. high 72.15 476.3 521.10 1154.20 0 20 40 60 80 100 low medium high low medium high low medium high d ry m at te r (g m -2 ) management practices stem leaf flower c a a d bcbc d d b 06 nov 25 nov 14 dec fig. 2. dry matter production at flowering and their distribution in different plant parts under different management practices at different sowing dates under low management practices the total dry matter produced from 25 november and 14 december sowing was identical. the highest dry matter accumulation in stem (52 g m-2), leaf (31.6 g m-2) and flower (9.6 g m-2) was recorded at 06 november sowing with high management practices and the lowest dry matter in stem (4.4 g m-2), leaf (3.6 g m-2) and flower (1.2 g m-2) at 14 december sowing with low management practice. it might be due to prevailing high temperature at flowering stage that increased photo-respiration and reduced net photosynthesis resulted in lower dry matter production (sage and sharkey, 1987). wellmanaged plants grown at late and high temperature showed higher dry matter production than poor managed one probably due to higher balanced between photorespiration loss and production of photosynthates. yield and yield attributes plant populations, plant height, number of branches plant-1, number of siliqua plant-1, seeds siliqua-1, 100-seed weight and seed yield of mustard showed significant difference in different sowing dates and management practices (table 4). the highest population (70 plant m-2) was recorded from 14 december sowing with low management practices and the lowest (52 plant m-2) from 06 november sowing with same management practices. the tallest plant was recorded from 06 november sowing with high management practices (108.20 cm), which was identical with medium management practices at the same date of sowing (99.50 cm) and high management practices at 25 november sowing (101.60cm). the minimum plant was recorded from 14 december sowing with low management practices (69.93 cm). significantly the highest number of branches was recorded from 06 november sowing with high management practices (8 plant-1). the lowest branches were recorded at 25 november sowing with low management practices. sown on 06 november sowing with high management practices also produced the maximum number of siliqua (84 plant-1) which was followed by medium management practices at the same date of sowing (70 plant-1) and 50 khan et al. high management practices at 25 november sowing (67 plant-1). the lowest number of siliqua was recorded from 14 december sowing with low management practices (19 plant-1). high temperature at flowering and siliqua formation stages enhanced flower and siliqua abscissions that reduced the number of siliqua (sinaki et al., 2007). the maximum reduction in siliqua at 14 december sowing could be due to floral sterility caused by high temperature (morrison and stewart, 2002). seed yield of mustard varied significantly under different sowing dates and management practices. the maximum seed yield also recorded from 06 november sowing with high management (1569 kg ha-1) which was identical with high management practices at 25 november sowing (1534 kg ha-1). the lowest seed yield was obtained from 14 december sowing with low management practices (435 kg ha-1) whereas at high management practices crop yielded 1183 kg ha-1. high temperature during reproductive phase is a primary constraint to its production. the lower seed yield at 14 december sowing might be due to prevailing high temperature (fig. 1) during flowering to maturity. the results are in agreement with the findings of rao et al. (1992). seed yield reduction of mustard varied from timely sowing to different sowing dates under different management (table 4). table 4. yield contributing characters and yield of mustard grown at different sowing dates under different management practices during rabi season, 2014-2015 treatments sowing dates management plant population (m-2) plant height (cm) branches plant-1 (no.) siliqua plant-1 (no.) seeds siliqua-1 (no.) 100seed wt (g) seed yield (kg ha1) 06 nov. low 52 77.33 3.8 26.0 19 0.29 620 medium 56 99.50 6.4 70.0 20 0.30 1245 high 52 108.2 7.8 83.8 24 0.31 1569 25 nov. low 67 72.20 1.3 20.3 20 0.29 583 medium 61 94.07 5.2 43.7 23 0.30 1060 high 59 101.6 5.5 67.4 23 0.31 1534 14 dec. low 70 69.93 2.5 18.9 18 0.29 435 medium 61 77.40 3.9 34.3 21 0.31 889 high 63 83.27 4.5 55.7 21 0.31 1183 lsd (0.05) 6.05 10.37 0.70 13.35 ns ns 155.5 cv (%) 5.68 6.69 8.62 16.07 7.90 5.31 8.63 seed yield reductions at 14 december sowing compared to 06 november sowing under low, medium and high management practices were 30, 29 and 25%, respectively. the seed yield reductions were 72, 43 and 25% under low, medium and high management at 14 december sowing, respectively compared to high management practices at 06 november sowing. better seed yield in well-managed plants at 14 december sowing could be due to higher accumulation of compatible osmolytes which might helped to increase water retention in plants for better stomata regulation and increased photosynthesis. conclusion from the above findings, it may be concluded that mustard crop is vulnerable to sowing dates induced temperature variability. developmental events were badly affected due to late sowing of seeds on 14 december. yield reduction may be reduced to some extent through 51 impact of sowing date induced temperature and management adopting high management practices. the highest seed yield (1569 kg ha-1) was recorded from 06 november sowing with high management practices while the lowest seed yield (435 kg ha-1) from 14 december sowing with low management practices. at high management practices the crop yielded 1183 kg ha-1 at 14 december sowing. yield reduction at late sowing condition was reduced to some extent with high management practices. references aggarwal, p. k., 2003. impact of climate change on indian agriculture. plant biology, 30, pp.189198. angadi, s. v., h. w. cutforth, b. g. mcconkey and y. gan. 2003. yield adjustment by canola grown at different plant populations under semiarid conditions. crop science. 43: 13581366. bbs (bangladesh bureau of statistics). 2013. statistical yearbook of bangladesh. bangladesh bureau of statistics, statistics division, ministry of planning, govt. people’s republic of bangladesh. cakmak, i. 2002. plant nutrition research: priorities to meet human needs for food in sustainable ways. plant soil. 247: 3-24. ipcc, 2007. climate change 2007. impacts, adaptation and vulnerability. working group ii contribution to fourth assessment report of the 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indian mustard (brassica juncea) at different phonological stages under late sown condition. indian j. plant physiol. 19(3): 238-243. thomas, p. 1984. canola growers’ manual. canola council of canada. 301-433. main st., winnipeg. canada. waraich, e. a., r. ahmad, m. ashraf, y. saifullah and m. ahmad. 2011. improving agricultural water use efficiency by nutrient management in crop plants. acta agriculturae scandinavica, section bsoil & plant sci. 61(4): 291-304 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.banglajol.info port 443 bangladesh agron. j. 2014, 17(1): 89-94 variations in salinity tolerance of selected mango rootstocks r. k. roy1, m. robbani2, m. ali2, s. k. bhowal3*, a. n. m. erfan4 1& 4m.s. student in horticulture, patuakhali science and technology university, bangladesh 2professor, department of horticulture, patuakhali science and technology university, bangladesh 3scientific officer (agronomy), on-farm research division, bangladesh agricultural research ins., noakhali, bangladesh *corresponding author: shamal.bau@gmail.com key words: mango rootstock, salinity tolerance abstract an experiment was conducted at the germplasm centre, department of horticulture, patuakhali science and technology university (pstu) during the period from july 2011 to march 2013 to study the performance of selected mango rootstocks in the saline area in bangladesh. the experiment consisted of four mango rootstock lines collected from rangpur, dumki, khulna and kuakata, and five salinity treatments namely control (0 dsm-1), low (4 dsm-1), medium (6 dsm-1), high (8 dsm-1) and very high (10 dsm-1). a two factor experiment was conducted in a randomized complete block design (factorial) with four replications. results revealed that rootstock line and salinity levels had significant influences on various crop characters viz. length of rootstocks, diameter of rootstocks, number of leaves and percent rootstocks success and survivability. in case of rootstocks, the longest rootstock length (41.38 cm), highest number of leaves (37.58) and survivability (71.73%) were recorded in rangpur line. in case of salinity treatments, rootstock diameter (16.09 mm), number of leaves/graft (36.47) and survivability (67.37%) were recorded in low salinity treatment. interaction of rootstock lines and different salinity treatments showed significant variation on the length and diameter of rootstocks at 120 dat. the maximum diameter of rootstock (17.63 mm) was recorded in high (8 dsm-1) salinity treatment in rootstock line of kuakata, followed by the same stages of rootstock lines of khulna (17.56 mm). the longest rootstock (46.75 cm) was recorded in control treatment (0 dsm-1) with rootstock line of rangpur followed by the same stages of rootstock (41.75 cm) with medium salinity treatment (6 dsm-1). rangpur rootstock line performed best from 0-8 dsm-1 salinity. the overall salinity tolerance was graded as follows: rangpur rootstock line > dumki rootstock line > kuakata rootstock line > khulna rootstock line. introduction mango (mangifera indica l.) is one of the most popular and commercially important fruits in bangladesh which is known as the “king of tropical fruits”. it belongs to the family anacardiaceae which is believed to have originated in the eastern india, assam, burma or in the malayan region (mukherjee, 1997). it has been cultivated in this sub-continent from 4000 years ago (candole, 1984). mango is grown in wide geographical area particularly in india, pakistan, brazil, mexico, the philippines, indonesia, thailand and srilanka. in bangladesh mangoes are grown everywhere, but the commercial and good quality grafted mangoes grown in the north-western districts and unknown varieties (seedling mangoes) are grown in the south eastern and other part of the country (bhuyan, 1995). mango ranks third among the tropical fruits grown in the world with the total production of 28848 thousand metric tons (fao, 2002). in bangladesh it ranks first in terms of area and third in production. it occupies an area of about 51.01 thousand hectares, with the production of 243 thousand metric tons of fruits (bbs, 2004). in bangladesh, a general decreasing trend in area and production of mango is observing during 1994-95 to 2003-04 (bbs, 2004). because, about 90% existing mango plants are raised from seeds which are mostly tall in nature with a large canopy (hossain, 1994). thus, it is difficult to incorporate tall and large sized mango varieties in limited area. these are the major reasons of diminishing mango production area. mailto:shamal.bau@gmail.com 90 roy et al. the other reasons behind this are lack of suitable variety (sarder et al., 1995), unavailability of suitable planting materials etc. grafted mango plants are true-to-type, require less area and start bearing earlier than the plants raised from seed. now a day’s using of epicotyle grafting in mango is a practice with good success for rapid multiplication of mango. at present, scion with the same polythene strip is used for graft joint. but research findings on these aspects in bangladesh are very limited or scanty. various factors influence the success and survivability of mango graft, viz. time of operation, grafting method, defoliation period of scion, maturity of stock and scion, wrapping technique of scion, leaf retention on rootstock and variety etc. among these, physiological maturity of stock and scion wood are very important factors for higher success, survivability and growth of grafts (kains and mc question, 1958; brahmachare et al., 1999). the information or research work with mango in saline area of southern belt is very limited. mango production is hampered due to restricted growth of the plant, root expansion hampered, low success and survivability due to high salinity. considering the above facts the present research work was undertaken to study the salinity tolerance of selected mango rootstocks. materials and methods the experiment was conducted at the germplasm centre, department of horticulture, patuakhali science and technology university (pstu), during the period from july 2011 to march 2013. the experimental area was situated under the sub-tropical monsoon climate, which is characterized by high temperature and heavy rainfall during the months of july to september and scantly rainfall associated with moderate low temperature during the rest period of the year. the soil of the experimental area was silty loam in texture belonging to the gangas flood plain of aez 13 having non-calcareous dark grey flood plain soil. the selected area was a medium high land. it was fertile, well drained and slightly acidic with the ph varying from 5.5 to 6.8 (barc, 1989). the experiment consisted of two factors i.e. factor-a: four type of mango rootstocks viz. r1 = rangpur line, r2 = khulna line, r3 = dumki line, r4 = kuakata line and factor-b: five level of soil salinity viz. s0 = control (0 dsm -1), s1 = low (4 dsm -1), s2=medium (6 dsm -1), s3 = high (8 dsm-1), s4 = very high (10 dsm -1). a two factor experiment was conducted in a factorial randomized complete block design with four replications. healthy and heavy stones of mango fruits of unknown cultivars were collected and placed in a bucket of water. only those stones that sunk and touched the bottom of bucket (containing water) were selected. about 1000 stones were selected for this process, which were uniform in size and shape. the stones were placed in polybags containing a mixture of soil and cowdung at the ratio of 1:1. one stone was placed in one polybag. after placing the seeds were germinated within 15 to 30 days. the experimental pots were made by earthen, containing 2-3 aeration holes at bottom for removal of excess water. total 480 experimental pots were filled by soil; well decompose cowdung, sand & small pitches of broken stones at the ratio of 1:1:1:1. nearly one and a half year mango rootstocks collected from four different types of mango cultivar which were raised in polybags previously & transplanted to the experimental pots. the healthy, vigorous, uniform in size and growth, pest and disease free rootstocks was selected for the experiment. pots containing healthy and uniform size rootstocks were raised in each rootstock line. intercultural operations like irrigation, weeding, application of fertilizer, spraying of insecticides and fungicide were given whenever needed for the good health of stock plant. four different rootstock lines were collected from rangpur, dumki, kuakata and khulna region. at first rootstocks were separated from different types of rootstock by their proper identity through individual tagging. four rootstock lines were arranged according to their identical number for properly data collection as well as performance review of different rootstock lines. all necessary measures were adopted to make the pot free from weeds and create a favorable environment to ensure proper growth and development of grafted plants. weeding and mulching were done whenever necessary during the period of investigation. the channels, made around each pot were connected to the main drain for rapid removal of excess rain water. proper shades were provided with the help of bamboo and coconut leaf until the grafts were in good condition in growth. sometimes the shade was removed to 91 salinity tolerance of mango rootstocks expose the plant to the direct sunlight for their proper growth. as a preventive measure against insect, pest and disease, spraying with insecticide and fungicides were done following a routine schedule. for this, diazinon and diathane m-45 @ 2ml liter-1 of water were applied at 7-10 days interval from 2-3 weeks after grafting and continued up to the last date of recording final data. the means of all the treatments were calculated and compared by least significant difference (lsd) test at 5% level of probability (gomez and gomez, 1984). results and discussion effect of rootstock significant variation was noticed in the growth of rootstocks from 30 to 120 days after transplanting (table 1). at 30 das, rangpur and khulna rootstock was similar and higher than the rest. similar trend was recorded at 60 dat and 90 dat. there was trend to increase length with the advancement of days. the longest length of rootstock was found in rangpur rootstock line (41.38 cm) while the shortest length of rootstock found in kuakata rootstock line (34.25 cm) at 120 days after transplanting. significant variation was also noticed in the number of new leaves from 30 to 120 days after transplanting (table 1). number of leaves showed maximum at khulna line followed by rangpur at 30 dat. similar trend was found at 60 and 90 dat but there were no significant difference at 90 and 120 dat. after initial success, the rootstocks were observed for 120 days, some rootstock died during this period. at the end of 120 days, the percentage of rootstock survival was recorded and the percentage of rootstock survival was presented in table 1. the highest rootstock survival (71.73%) was obtained from rangpur rootstock line while other rootstock survivability among the lines were similar. table 1. main effect of rootstock lines on the length of rootstocks, leaves number and rootstock survivability at different days after transplanting rootstock line rootstock length (cm) no. of leaves rootstock survivability at 120 dat (%) 30 days 60 days 90 days 120 days 30 days 60 days 90 days 120 days rangpur 39.50a 40.10a 40.53a 41.38a 22.38ab 24.85ab 31.77 37.58 71.73a dumki 32.95b 33.40b 33.78b 34.63b 15.99b 19.80b 24.27 27.02 60.90b khulna 36.67a 36.97ab 37.28ab 37.97ab 25.33a 28.35a 31.52 33.70 57.39b kuakata 32.90b 33.25b 33.58b 34.25b 16.05b 18.42b 25.08 28.40 56.73b lsd (0.05) 3.57 3.74 3.72 3.74 8.014 8.24 ns ns 4.89 cv (%) 7.18 7.42 7.31 7.20 28.71 25.75 26.85 23.91 5.66 effect of salinity significant variation was found among different salinity treatments in the present experiment (table 2). there was no significant difference in salinity treatment at 30 dat except very high salinity level. similar trend was followed upto 120 dat. but maximum length of rootstock (39.72 cm) was recorded at high salinity level while shortest rootstock (33.81 cm) was observed in very high (10 dsm-1) salinity treatment at 120 dat (table 2). very high salinity treatment lowered the water potential of the roots, and this caused quick reductions in growth rate along with a suite of metabolic changes identical to those caused by water stress. the effect of salinity treatments on the diameter of rootstocks has been shown in the fig. 1. significant variation was found different salinity treatments. after 120 dat, high salinity treatments was found maximum diameter of rootstock (16.09 mm) while the lowest diameter of rootstock in very high (10 dsm-1) salinity treatment (13.52 mm) (fig. 1). significant variation was found different salinity treatments on the rootstock survivability in the experiment but number of leaves plant-1 was not significantly influenced by salinity treatment. rootstock survivability (%) was minimum at low level of 92 roy et al. salinity followed by control. srivastava et al. (1989) also reported that increases the salinity treatment decreases the rate of survivability of mango. table 2. main effect salinity treatment on the length of rootstocks, leaves number and rootstock survivability at different days after transplanting salinity treatment rootstock length (cm) no. of leaves rootstock survivability (%) 30 days 60 days 90 days 120 days 30 days 60 days 90 days 120 days control 34.91ab 35.59ab 35.91ab 36.78ab 19.44 23.22 28.78 32.81 64.77ab low 36.97a 37.34a 37.72a 38.47a 20.56 24.09 33.09 36.47 67.37a medium 35.06ab 35.44ab 35.91ab 36.50ab 17.59 20.56 25.69 28.66 60.69bc high 38.13a 38.59a 38.91a 39.72a 21.61 24.72 28.06 31.25 59.64c very high 32.47b 32.69b 33.00b 33.81b 20.47 21.69 25.19 29.19 55.97c lsd (0.05) 3.57 3.74 3.72 3.74 ns ns ns ns 4.89 cv (%) 7.18 7.42 7.31 7.20 28.71 25.75 26.85 23.91 5.66 control= 0 dsm-1, low= 4dsm-1, medium = 6 dsm-1, high =8 dsm-1, very high =10dsm-1 fig. 1. effect of salinity treatments on the diameter of rootstocks at different days after transplanting interaction effect of rootstocks and salinity interaction of rootstock lines and different salinity treatments showed significant variation on the length of rootstocks at 120 dat (fig. 2). the periodical data showed that more increase in length of rootstocks recorded at 120 dat. the longest rootstock (46.75 cm) was recorded when control salinity treatment (0 dsm-1) with rootstock line of rangpur followed by the same stages of rootstock (41.75 cm) with medium salinity treatment (6 dsm-1). the shortest rootstock (29.88 cm) was recorded in the rootstock line of kuakata with very high salinity (10 dsm-1) treatment (fig. 2). 93 salinity tolerance of mango rootstocks fig. 2. interaction of rootstocks and salinity treatments on the rootstock length at different dat interaction of rootstock lines and salinity treatment had significant influence on the diameter of rootstock at 120 dat (fig. 3). there was trend to increase rootstock diameter with the advancement of days 30 to 120 dat. the maximum diameter of rootstock (17.63 mm) was recorded in high (8 dsm-1) salinity treatment into the rootstock line of kuakata, followed by the same stages of rootstock lines of khulna (17.56 mm) with high salinity treatment (fig. 3). the minimum diameter (12.38 mm) of rootstock line of dumki was recorded with very high (10 dsm-1) salinity treatment. fig. 3. interaction of rootstocks and salinity treatments on the diameter of rootstock at different dat references barc. 1989. fertilizer recommendation guide. bangladesh agriculture research concil, new airport road, farmgate, dhaka-1207. pp.11-41. bbs. 2004. monthly statistical bulletin, bangladesh bureau of statistics, statistics division, ministry of planning, government of the people’s republic of bangladesh. dhaka, p.49. brahmachari, v. s., a. r. singh and r. c. bishwas. 1999. effect of period of defoliation of scion and age of rootstock on success of epicotyl grafting in mango (mangifera indica l.) cv. amrapali. orissa j. hort. 27: 1-4. 94 roy et al. bhuyan, m. a. j. 1995. mango. in: fruit production manual, horticulture research and development project, dae-padc. p.197. candole, a. d. 1984. origin of cultivated plants. vegal paul trench and co., london pp.1-67. fao. 2002. production yearbook. statistical series no. 163. food and agriculture organization, rome, italy, p.182. hossain, a. k. m. a. 1994. production technology of mango. horticulture research centre, bari, joydebpur, gazipur. l22p. kains, m. g. and m. mcquestion. 1958. propagation of plants. grage judd publishing company, inc., new york. p.225. mukherjee, k. u. 1997. introduction: botany and importance. in: the mango: botany, production and uses. 1st edition (r. & litz ed.), cab international, wallingford, uk. pp.1-19. sarder, p. k., d. guha and m. a. uddin. 1995. assessment of introduced mango germplasm under bangladesh condition. annual report on mango improvement, regional horticulture research station, bari, nawabganj-6300, bangladesh. p.10. srivastava, k. c., n. p. singh, m. s. rajput, g. c. sinha and b. lai. 1989. performance of mango plants raised by different methods. acta hort. 231: 209297. grain development of wheat in 2010-12 bangladesh agron. j. 2016, 19(2): 79-85 grain growth of wheat under prevailing air temperature m.a.k. mian1, m.r. islam2, j. hossain2 and m.a.aziz1 agronomy division, bari, joydebpur1 and rars, ishwardi2 bangladesh agricultural research institute, joydebpur, gazipur 1701 key words: phenological duration, grain growth, wheat, air temperature abstract an experiment was conducted at the regional agricultural research station, ishwardi, pabna in two consecutive years of 2010-2011 and 2011-2012 to quantify the effect of temperature on phenological duration and grain growth of wheat. temperature variation was created by changing sowing date (15 november=s1, 30 november=s2, 15 december=s3 and 30 december=s4). results revealed that reproductive phase was more sensitive to high temperature as compared to vegetative phase of wheat. reproductive phase reduced from 54 to 37 days in 2010-2011 and from 64 to 34 days in 2011-2012 as influenced by higher air temperature under late sowing. duration of reproductive phase was strongly and negatively correlated with mean air temperature (r=-0.64 to -0.96 at p<0.01). maximum grain growth (49.1250.18 mg grain-1) was recorded at 55 days after anthesis in 30 november sowing in both the years. grain growth was negatively correlated (r=-0.80 at p<0.01) with mean air temperature during grain growth period. grain yield was the highest (4560-6080 kg ha-1) in 30 november sowing, afterwards it reduced in both the years. grain yield was negatively correlated (r=-0.70 at p<0.01) with mean air temperature of grain growth period. rising of air temperature at grain filling stage subjected to reduced grain yield of wheat. effect of temperature on grain yield of wheat can be explained about 88% by the function of y= -14910+ 2069x-52.67x2 (r² = 0.88). rising of one degree (oc) temperature above optimum (19.64 0c) grain yield reduced @ 53 kg ha-1 (0.98%). introduction wheat is an important cereal crop in bangladesh covering an area of 436814 ha with an annual production of 1347926 metric tons (bbs, 2016). wheat is winter season crop in bangladesh. but winter is becoming shorter due to climate change and global warming. it is estimated that temperature would be increased about 1.4°c by 2050 and 2.4°c by 2100 in bangladesh (oecd, 2003). therefore, wheat production may be reduced. as the global warming, temperature has significant effect on crop production. due to global warming, environmental scientists have given research emphasis on temperature effect and other weather elements. bangladesh has experienced climate changed effect due to global warming (karim, 2015). winter is coming shorter and temperature is rising in winter affecting the winter crops in bangladesh (mian et al., 2016). wheat requires different temperatures at different stages of plant growth and development. the optimum temperature for wheat ranges from 20° to 25° c. temperature above 30 0c at grain filling stage leads the crop to forced maturity and retards grain formation resulting yield loss (uddin et al., 2015). rising of air temperature in later part of winter affects the grain development and reduces grain growth resulting lower yield of wheat (bari, 2016). sometimes, farmers cannot sow wheat timely due to excess soil moisture or standing crop of t. aman rice in the field. consequently, delay sowing of wheat frequently subjects to high 80 mian et al. temperature stress in grain filling stage. on this account, farmers harvest lower yield of wheat (bari, 2016). temperature is the single most important climatic factor that affects the growth and development of crop plant (mian et al., 2013). it also influences the other different physiological process of the crop plant. temperature affects root and shoot growth, nutrient uptake, water absorption, photosynthesis, respiration, transpiration, translocation of photosynthate and other metabolic functions in the plant system (ali and sarker, 2016). high temperature affects phenology, growth and yield of wheat (chakrabarti et al. 2013). different planting time and year to year temperature variation would affect the grain growth and grain yield of wheat. the present study was undertaken to quantify the effect of temperature on phenology and grain growth of wheat under late sown irrigated condition. materials and methods the experiment was conducted at the regional agricultural research station, ishurdi, pabna during the rabi season of 2010-2011 and 2011-2012. the experiment was laid out in a rcb design with four replications. unit plot size was 6 m × 5 m. soil texture of the experimental site was sandy loam. wheat var. bari gom-26 was used as test crop in the experiment. the treatment was 15 november= s1, 30 november= s2, 15 december= s3 and 30 december= s4. the crop was fertilized with 80-35-5520-1.2 kg ha−1 of n-p-k-s-b. all nutrients including 2/3 of n were applied as basal. rest of 1/3 of n was top dressed at cri stage. three irrigations were applied at cri, booting and grain filling stages. weed control was done at 25 days after emergence by spading in between rows. no disease and insect control is needed. data on duration of phenological phases, grain weight at 5 days interval starting from 20 days after anthesis, grain yield, and daily air temperature were recorded. air temperature was calculated on the basis average of daily maximum and minimum temperature. crop was harvested on 25 march, 1 april, 2 april and 4 april respectively in 2011 and on 15 march, 22 march, 28 march and 7 april, respectively in 2012. data were analyzed and presented in tables and figures. optimum temperature was estimated using the functional model as below (mian et al., 2011). y=a + bxcx2 y=grain yield of wheat (dependent variable) a=intercept (constant) x=mean air temperature (independent variable) b and c are the rates of change of grain yield due to change of air temperature optimum temperature for maximum grain yield of wheat (yw)= (-b)/2c results and discussion effect of sowing date and air temperature on phenological duration phenological duration is changed due to change of sowing date (table 1). duration of vegetative phase was found maximum (68 days) in 30 november sowing but minimum (34-37 days) in 30 december sowing in both the years. duration of reproductive was longer (54-64) in 15 november sowing; afterwards it decreased chronologically with the shortest (34-37 days) in 30 december sowing. field duration was exhibited higher (112-122 days) in earlier sowing as compared to later sowing. similar results also have been reported by ali and sarker (2016). phenological duration showed negative correlation with air temperature (table 2). duration of reproductive phase showed strong and negative correlation (r=-0.64 to -0.96 at p< 0.01) with air temperature in both the years. field duration also exhibited strong and negative correlation (r=-0.82 to -0.93 at p< 0.01) with air temperature in 2010-2011 and 2011-2012. correlation 81 grain growth of wheat under prevailing air temperature between duration of vegetative phase and air temperature was very weak but negative (table 2). the results are in agreement with the findings of others (wheeler et al., 1996 and mian et al., 2013). effect of sowing date and air temperature on grain growth effect of sowing date on grain growth has been presented in fig.1 and fig.2. sowing in 15-30 november exhibited higher trend of grain growth in both the years (fig. 1 and fig. 26) as compared to later sowing. grain growth was maximum (49.12-50.18 mg grain-1) in 30 november sowing followed by 15 november sowing while the lowest in 30 december sowing in both the years. grain growth showed negative and strong correlation (r=0.80 at p<0.01) with air temperature (table 2). the results indicated that grain growth reduced due to higher temperature in late sown condition of wheat. similar results also have been described by khan and aziz (2015), and (uddin et al., 2015). effect of sowing date and air temperature on grain yield grain yield was the highest (4560-6080 kg ha-1) in 30 november sowing and the lowest in 30 december sowing in both the years (table 4). the results expressed that grain yield reduced in later sowing as compared earlier sowing. grain yield showed negative and strong correlation (r= -0.71 to -0.79 at p<0.01) with air temperature (table 4). the results revealed that rising of air temperature at later sowing reduced grain growth resulting poorer grain yield of wheat. the results are in agreement with the reports of bari (2014) and bari (2016). effect of temperature on grain yield of wheat can be explained about 88% by the function of y=-14910+ 2069x -52.67x2 (r² = 0.88) (fig. 3). by using the function it was estimated that rising of one degree (oc) temperature above optimum (19.64 0c) grain yield reduced @ 53 kg ha-1 (0.98%). similar results also have been described by chakrabarti et al. (2013). conclusion reproductive phase as well as field duration of wheat would be reduced as influenced by air temperature at later sowing (after 30 november). grain growth was higher in 30 november sowing and it was negatively correlated (r=-0.80 at p<0.01) with mean air temperature. rising of one degree (oc) temperature above optimum (19.64 0c) grain yield would be reduced @ 53 kg ha-1 (0.98%). table 1. phenological duration of wheat under different sowing dates (2010-2011 and 2011-2012) year sowing date vegetative phase (days) reproductive phase (days) field duration (days) 2010-2011 15 november 58 54 112 30 november 68 45 113 15 december 63 39 102 30 december 56 37 93 2011-2012 15 november 56 64 122 30 november 68 45 114 15 december 65 38 105 30 december 64 34 98 mean 62 45 107 stdev 5 10 10 82 mian et al. table 2. effect of air temperature on phenological duration of wheat (2010-11and 2011-2012) year correlation between correlation co-efficient (r) 2010-2011 duration of vegetative phase and air temperature -0.26ns duration of reproductive phase and air temperature -0.96** field duration of and air temperature -0.93** 2011-2012 duration of vegetative phase and air temperature -0.14ns duration of reproductive phase and air temperature -0.64** field duration of and air temperature -0.82** ** indicates significant at 0.01 level of probability, ns = not significant table 3. effect of air temperature on grain growth of wheat (2010-2011 and 20112012) year sowing date air temperature 0c (reproductive phase) grain wt. (mg grain-1) correlation co-efficient (r) 2010-2011 15 november 18.60 48.22 -0.74** 30 november 22.86 50.18 15 december 24.09 42.57 30 december 25.14 39.21 2011-2012 15 november 20.16 47.50 -0.69** 30 november 23.17 49.12 15 december 24.42 42.45 30 december 26.42 39.24 mean 23.11 44.81 -0.80** std 2.59 4.46 combined of 2010-2011 and 20112012 ** indicates significant at 0.01 level of probability table 4. effect of air temperature on grain yield of wheat (2010-2011 and 20112012) year sowing date air temperature 0c (reproductive phase) grain yield (kg ha-1) correlation co-efficient (r) 2010-2011 15 november 18.60 5920 -0.79** 30 november 22.86 6080 83 grain growth of wheat under prevailing air temperature 15 december 24.09 4380 30 december 25.14 3580 2011-2012 15 november 20.16 4200 -0.71** 30 november 23.17 4560 15 december 24.42 4040 30 december 26.42 3000 mean 23.11 4470 -0.70** std 2.59 1064 combined of 2010-2011 and 20112012 ** indicates significant at 0.01 level of probability fig. 1. grain growth of wheat as affected by different dates of sowing (s1 =15 november, s2= 30 november, s3=15 december and s4=30 december) in 2010-2011 84 mian et al. fig. 2. grain growth of wheat as affected by different dates of sowing (s1 =15 november, s2= 30 november, s3=15 december and s4=30 december) in 2011-2012 fig. 3. functional relationship between air temperature and grain yield of wheat reference y = 14910+ 2069x -52.67x2 r² = 0.88 y ie ld (k g/ ha ) mean air temperature (oc) 85 grain growth of wheat under prevailing air temperature ali, m. z. and m. a. i. sarker. 2016. effect of sowing time based temperature variation on growth, yield and seed quality of gardenpea. in: unfavourable ecosystem. crop production under high temperature and drought stress. agronomy division, bangladesh agril. res. int. gazipur 1701. pp. 1-7. bari (bangladesh agricultural research institute). 2014. interaction effect of different locations, dates of sowing and genotypes on yield contributing 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of wheat as influenced by variety and sowing date. bangladesh agron. j. 18(2): 97-104 wheeler, t. r., t. d. hong, r. h. ellis, g. r. batts, j. i. l. morison and p. hadley. 1996. the duration and rate of grain growth, and harvest index, of wheat (triticum aestivum l.) in response to temperature and co2. j. exp. bot47: 623630. http://link.springer.com/article/10.1007/s40502-013-0002-6#author-details-1 http://link.springer.com/article/10.1007/s40502-013-0002-6#author-details-2 http://link.springer.com/article/10.1007/s40502-013-0002-6#author-details-3 http://link.springer.com/article/10.1007/s40502-013-0002-6#author-details-4 http://link.springer.com/article/10.1007/s40502-013-0002-6#author-details-5 86 mian et al. reference ali, m. z. and m. a. i. sarker. 2016. effect of sowing time based temperature variation on growth, yield and seed quality of gardenpea. in: unfavourable ecosystem. crop production under high temperature and drought stress. agronomy division, banglades... bari (bangladesh agricultural research institute). 2014. interaction effect of different locations, dates of sowing and genotypes on yield contributing characters and yield of wheat. in: annual report. wheat res. centre. bangladesh agril. res. int. na... bari (bangladesh agricultural research institute). 2016. development of yield model of modern wheat varieties under late sown heat stress environment. in: annual report. wheat res. centre. bangladesh agril. res. int. nashipur, dinajpur. pp. 110-119. bbs (bangladesh bureu statistics). 2016. yearbook of agril. statistics-2015. bangladesh bur. stat. ministry of planning. govt. people’s republic of bangladesh. pp.78-81. chakrabarti, b., s. d. singh, v. kumar, r. c. harit and s. misra. 2013. growth and yield response of wheat and chickpea crops under high temperature. indian j. plant physiol. 18: 7-14. bangladesh agron. j. 2014, 17(1): 81-88 effect of spacing on p and zn uptake of local t. aman rice varieties in khulna area s. parvin1, m. m. islam2, m. k. mondal3, k. g. quddus2 and a. m. mahmud4 1lecturer, agriculture studies, govt. bangabandhu college, rupsha, khulna 2professor, agrotechnology discipline, khulna university, khulna 3collaborative research scientist, irri, dhaka, bangladesh 4ngo focal person, dak diye jai corresponding author: parvin.shahanaz96@gmail.com key words: t. aman, spacing, phosphorus, zinc abstract a field experiment was conducted at the agronomy field of khulna university, khulna during t. aman season to evaluate the effects of spacing on nutrient content and total uptake of phosphorus and zinc by grain and straw of traditional rice of khulna region. the experiment was laid out in split-plot design with three replications assigning three varieties viz., jotai, bashfulbalam, ranisalute and three spacings viz., 30 cm x 30 cm, 40 cm x 40 cm and 50 cm x 50 cm. the variety was assigned in main plot and spacing in sub plot. the plot was fertilized with 40-50-35-5 kg of urea-tsp-mop and zns0 4 ha -1 respectively. the results indicated that the single effect of variety and spacing on p and zn content in grain and straw varied significantly while the straw p content was found insignificant. the interaction effect of variety and spacing on p and zn content was found significant in all the treatments. the highest p and zn content of grain was found from the variety ranisalute at 50 cm x 50 cm (v 3 s 1 ) but in straw from ranisalute x 40 cm×40 cm (v 3 s 2 ) and bashfulbalam x 30 cm × 30cm (v 2 s 1 ), respectively. the total uptake of p and zn was found the highest from jotai variety at 30 cm x 30 cm spacing. from the interaction it showed that the highest p and zn uptake was found from jotai x 30 cm × 30 cm (v 1 s 1 ) and the lowest from ranisalute x 50 cm x 50 cm (v 3 s 3 ). the study indicated that though wider spacings of 40 cm x 40 cm and 50 cm x 50 cm increased the number of tillers hill-1 and nutrient uptake but it cannot increase the nutrient uptake and grain yield ha-1. so, 30 cm x 30 cm spacing showed positive relationship on nutrient uptake than 40 cm x 40 cm and 50 cm x 50 cm spacing. introduction rice is the staple food of bangladesh. it contributes about 90% of food grains and covers about 80% of total cropped area of the country. it provides about 70% of the calories consumed by 160 million people of bangladesh (ais, 2008). in order to increase the yield of rice plants the availability and uptake of proper and judicious use of fertilizers containing major and micronutrient is very important. the practice of intensive cropping with modern varieties causes a marked depletion of inherent nutrient reserve in soils of bangladesh. consequently in addition to n, p and k deficiencies, some other nutrient such as zn, s and b deficiencies are being observed in many parts of the country (haque and jahiruddin, 1994). fertilizer is the most important input for rice production. for the best yield of rice plant along with nitrogen requirements, phosphorus and zinc is also needed. the application of p and zn can play important role in grain setting, increased grain yield and nutrient concentration of rice. phosphorus is important for the growth, reproduction, yield and quality of rice crop. tillering of rice plant is positively co-related with phosphorus. it also promotes root development and elongation capability of rice plant (hossain et al., 2009). zinc deficiency has been detected as the third major nutritional problem for bangladesh soil next to n and p limiting the growth of wetland rice. in some places of bangladesh yield loss due to zn deficiency 82 parvin et al. ranged from 10-18%. zinc plays an important role in many physiological functions of plants. planting densities exceed an optimum level competition among plants for macro and micro nutrients becomes severe consequently the plant growth stunted and grain yield decreases. the number of tillers per square meter is increased with the improvement of rice production (islam, 2001). however, scanty information is available about the effect of spacing on the uptake of nutrients particularly p and zn on rice. therefore, the present study was conducted to find out the effect of spacing on the uptake and content of p and zn of local t. aman rice varieties of khulna area. materials and methods the experiment was conducted in the field of agro technology discipline at khulna university during t. aman season. the soil was characterized by medium textured silty loam having ph value 7.5 and organic matter 3.80%. before raising seeds in the nursery, seeds were water soaked for 24 hours and these were kept in jute bags in dark conditions. after sprouting, the seeds were sown in wet seed bed. thirty days old seedlings were uprooted carefully from the nursery and transplanted as single seedling hill-1 on the well puddled experimental plots. three popular t. aman rice varieties viz, jotai (v 1), bashfulbalam (v 2) and ranisalute (v 3) were selected for the study. the varieties were planted in three different spacings viz, 30 cm x 30 cm (s1), 40 cm x 40 cm (s2), and 50 cm x 50 cm (s3). the variety was assigned in main plot and spacing in sub plot. the plot size was 4.0 m x 2.5 m. the land was fertilized with 40-50-35-5 kg of ureatsp-mop-znso 4 ha -1 respectively. the full dose of fertilizers and half of urea was applied as basal dose during final land preparation and the remaining half of urea was applied in two splits at active tillering and during panicle initiation stage. grain yield and straw yield were recorded from whole plot basis leaving boarder lines. grain yield was adjusted at 14% moisture content. in order to conduct chemical analysis during harvest five representative samples of grain and straw from each sub plot were collected. the collected samples were analysed and phosphorus (p) was determined by spectrophotometer and zinc (zn) by atomic absorption spectrophotometer. the data was analyzed following standard statistical procedures (gomez and gomez, 1984) using a computer operated program mstatc. results and discussion p concentration phosphorus content in grain differed significantly due to the main effect of variety and spacing but it was found insignificant in straw (table 1). it was ranged from 0.102% to 0.116% in grain and 0.030% to 0.032% in straw from the effect of varieties and 0.107% to 0.113% in grain and 0.028% to 0.032% in spacings. among three varieties the maximum p content of grain (0.116%) was found from ranisalute variety which was followed by bashfulbalm (0.115%) and jotai (0.102%). the content of p was found samilar (0.113%) in 50 cm x 50 cm and 30 cm x 30 cm spacing which was followed by 40 cm x 40 cm spacing in straw (0.107%). the grain content of p was higher compared to straw content of that in all treatments which supports the findings of yoshida (1981) that contents of phosphorus (p) is generally higher in the panicles than in the straw (leaves and culm). table 1. effect of variety and spacing on p and zn content of grain and straw treatments p (%) zn (ppm) grain straw grain straw v 1 (jotai) v 2 (bashfulbalam) v 3 (ranisalute) 0.102 0.115 0.116 0.032 0.031 0.030 26.17 36.94 37.61 37.33 40.17 34.28 83 spacing effect on p and zn content of local t. aman rice varieties level of significance 0.01 ns 0.01 0.01 lsd (0.01) 0.06899 1.220 2.821 s1 (30 cm x 30 cm) s2 (40 cm x 40 cm) s3 (50 cm x 50 cm) 0.113 0.107 0.113 0.032 0.032 0.028 32.11 32.72 35.89 39.50 37.44 34.83 level of significance 0.05 ns 0.01 0.01 lsd (0.01) 0.06899 1.220 2.821 cv (%) 7.00 24.51 1.67 3.47 interaction effect of variety x spacing was found statistically significant in both grain and straw (table 2). it was ranged from 0.095% to 0.0128% in grain and 0.025% to 0.037% in straw. the highest grain content (0.128%) was found from v 3s3 and the lowest (0.095%) from jotai x 30 cm x 30 cm (v 1s1). in straw the highest p content (0.037%) was found from ranisalute x 40 cm x 40 cm (v 3s2) and the lowest (0.025%) from both ranisalute x 50 cm x 50 cm (v3s3) and bashfulbalam x 40 cm x 40 cm (v2s2). zn concentration zn concentration in grain and straw was significantly affected by the main effect of variety and spacing. among three varieties the grain zn content was found the maximum (37.61 ppm) from jotai which was followed by bashfulbalam (36.94 ppm) and ranisalute (26.17 ppm). but in straw zn content was found the highest (40.17 ppm) from bashfulbalam and the lowest (34.28 ppm) from ranisalute. the highest zn content (35.89 ppm) was found from 50 cm x 50 cm and the lowest (26.17 ppm) from 30 cm x 30 cm spacing. in straw the highest zn content (37.44 ppm) was found from 40 cm x 40 cm and the lowest (34.83 ppm) from 50 cm x 50 cm spacing (table 2). interaction effect of variety x spacing was found statistically significant in both grain and straw zn content ranged from 24.67 ppm to 41.00 ppm in grain and 32.00 ppm to 43.33 ppm in straw (table 2). the highest (41.00 ppm) and the lowest (24.67 ppm) zn content in grain was obtained from ranisalute x 50 cm x 50 cm (v 3s3) and jotai x 30cm x 30cm (v 1s1), respectively. the straw content of zn was higher compared to grain content that confirms the findings of yoshida (1981). the highest (43.33 ppm) and the lowest (32.00 ppm) straw zn content was obtained from bashfulbalam x 30 cm x 30 cm (v 2s1) and ranisalute x 50 cm x 50 cm (v3s3), respectively. phosphorus uptake the interaction effect of variety x spacing on p uptake was shown in figure 1, 3 and 5. it was observed that variety jotai uptake the highest p than bashfulbalam and ranisalute (fig. 1, 3 and 5). the spacing 30 cm x 30 cm uptake the highest p than 40 cm x 40 cm and 50 cm x 50 cm. though wider spacing enhanced nutrient uptake but the highest grain yield was obtained from 30 cm x 30 cm spacing as a result the total uptake of p was obtained from 30 cm x 30 cm spacing. actually wider spacing promoted more tillering than lower spacing but tiller number per square meter is important for total uptake of nutrient than tillers hill-1 (islam, 2001). the interaction of jotai x 30 cm x 30 cm (v 1s1) uptake the highest p (4.85 kg ha-1) and the lowest (3.0 kg ha-1) was found from ranisalute x 50 cm x 50 cm (v 3s3) interactions. table 2. effect of variety x spacing interaction on p and zn content of grain and straw interaction (variety x spacing) p (%) zn (ppm) grain straw grain straw v 1s1 0.108 0.32 24.67 42.17 v 1s2 0.102 0.35 26.83 35.17 v 1s3 0.950 0.28 27.00 34.67 v 2s1 0.115 0.35 36.83 43.33 v 2s2 0.115 0.25 34.33 39.33 v 2s3 0.115 0.32 39.67 37.83 v 3s1 0.115 0.28 34.83 33.00 84 parvin et al. v 3s2 0.103 0.37 37.00 37.83 v 3s3 0.128 0.25 41.00 32.00 lsd (0.01) 0.07 ns 1.22 2.82 cv (%) 7.00 24.51 1.67 3.47 v 1 = jotai, v 2 =bashfulbalam, v 3 =ranisalute s 1 = 30cm x 30cm, s 2 =40cm x 40cm, s 3 =50cm x 50cm zinc uptake the interaction effect of variety x spacing on zn uptake was shown in figure 2, 4 and 6. it was observed that variety jotai uptake the highest zn than bashfulbalam and ranisalute (fig. 2, 4 and 6). the spacing 30 cm x 30 cm uptake the highest zn than 40 cm x 40 cm and 50 cm x 50 cm. though wider spacing enhanced nutrient uptake but the highest yield was obtained from 30 cm x 30 cm spacing. the interaction of jotai x 30 cm x 30 cm (v 1s1) uptake the highest zn (0.273 kg ha -1) and the lowest (0.156 kg ha-1) was found from ranisalute x 50 cm x 50 cm (v3s3). fig. 1. phosphorus uptake by jotai variety in three spacings fig. 2. zinc uptake by jotai variety in three spacings 85 spacing effect on p and zn content of local t. aman rice varieties fig. 3. phosphorus uptake by bashfulbalam variety in three spacing fig. 4. zinc uptake by bashfulbalam variety in three spacing fig. 5. phosphorus uptake by ranisalute variety in three spacing 86 parvin et al. fig. 6. zinc uptake by ranisalute variety in three spacing nutrient status of soil nutrient status of the experimental soil before planting and after harvest was shown in table 3. before planting the nutrient n, p, k, zn and s content of soil was 0.207%, 7.15 ppm, 0.36 meq. 100 g-1 soil, 0.46 ppm and 129.53 ppm, respectively. after harvest the n, p, k, zn and s content of soil were 0.250%, 4.17 ppm, 0.27 m.eq/100 g soil, 0.883 ppm and 218.38 ppm, respectively. recovery of p and zn was obtained from basal application of 50 kg p2o 5 ha -1 and 30 kg znso 4 ha -1. in the experimental plot the deficiency of p and zn was present before planting and different level of p and zn fertilizer was not applied in the treatment that’s why apparent recovery of these two nutrients was smaller than field experiments. the results indicated that added elements (p and zn) might have residual effect on the succeeding crop (jahiruddin et al., 1994). table 3. some important properties of the experimental soils parameters before planting after harvest texture silty loam silty loam ph 7.5 7.6 e.c 7.77 ds m-1 8.87ds m-1 organic matter 3.80% 5.17% total n 0.207% 0.25% exchangeable k 0.36 meq. 100 g-1 soil 0.27 meq. 100 g-1 soil exchangeable ca 27.50 meq. 100 g-1 soil 38.17 meq. 100 g-1 soil exchangeable mg 5.75 meq. 100 g-1 soil 7.78 meq. 100 g-1 soil available p 7.15 ppm 4.17 ppm total zn 0.46 ppm 0.883 ppm available s 129.53 ppm 218.38 ppm conclusion 87 spacing effect on p and zn content of local t. aman rice varieties the overall results of the present study showed that the single and interaction effect of variety and spacing showed significant influence on phosphorus and zinc content in grain and straw but the straw phosphorus content was insignificant from the single effect of variety and spacing. the uptake of phosphorus and zinc was found the highest in closer spacing than wider spacing. the number of tillers square meter-1 was more in closer spacing 30 cm x 30 cm than wider spacing 40 cm x 40 cm and 50 cm x 50 cm. so, it can be the concluded that the uptake of nutrient depends on number of tillers square meter-1 than number of tillers hill-1. references ais (agricultural information service). 2008. krishi dairy. agric. int. ser. dhaka. pp.20-22. brri (bangladesh rice research institute). 1989. annual internal review for 1989. bangladesh rice res. inst. gazipur-1701. pp.169-171. gomez, k. a. and a. a. gomez. 1984. statistical procedures for agricultural research. intl. rice res. inst. los banos, laguna, philippines. pp.97-116. haque, m. s. and m. jahirruddin. 1994. effect of single and multiple application of sulphur and zinc in a continuous rice cropping pattern. indian j. agric. res. 28(1): 9-14. hossain, m. b., m. jahiruddin, m. r. h. loppert, g. m. panaullah, m. r. islam and j. m. duxbury. 2009. the effects of iron plaque and phosphorus on yield and arsenic accumulation in rice. j. plant soil. 317: 167-176. islam, m. 2001. enhancement of and yield of boro rice through modification of sri (system of rice intensification) technique in terms of fertilizer management, spacing and seedling age. m. sc. thesis, dept. of agronomy. bau, mymensingh. jahiruddin, m., m. n. islam, m. a. hashem and m. r. islam. 1994. influence of sulphur, zinc and boron on yield and nutrient uptake of br2 rice. progress. agric. 59(1): 61-67. rahman, k. m. m., m. a. k. chowdhury, f. sharmeen, a. sarkar, m. a. hye and g. c. biswas. 2011. effect of zinc and phosphorus on yield of oryza sativa (cv.br-11). bangladesh res. pub. j. 4 (5): 351-358. yoshida, s. 1981. fundamentals of rice crop science. the intl. rice res. inst. los banos, laguna, philippines. 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.banglajol.info port 443 microsoft word 4. baj-220_revised.docx bangladesh agron. j. 2016, 19(1): 29-36 effect of sowing time based temperature variations on growth, yield and seed quality of garden pea m. z. ali1, m. a. aziz1, m. a. i. sarker1, s. mazumder2, s. k. paul1*, t. a. mujahidi3 m. s. a. khan1 and m. s. bhuiyan1 1agronomy division, bangladesh agricultural research institute, joydebpur, gazipur-1701, bangladesh. 2sher-e-bangla nagar adarsha mohila college, dhaka-1207 3scientific officer, plant breeding division, bangladesh agril. res. institute, joydebpur, gazipur-1701, bangladesh *corresponding author: santosh87dhaka@gmail.com key words: temperature, gardenpea, phenology, growth, yield, seed quality abstract a field experiment was conducted at the research field of agronomy division, bari, joydebpur, gazipur and ars, burirhat, rangpur to evaluate crop growth, yield and seed quality of garden pea in prevailing temperature at different sowing dates (10 november, 20 november, 30 november, 10 december, 20 december and 30 december). sowing date based temperature variations significantly affected the crop growth, tdm production, yield and seed quality of bari motorshuti-3. plants with november 20-30 sowing performed the best in respect of yield and yield contributing characters. however, with the delayed in sowing dates, the temperatures at the later growth phases were increased, while the grain growth duration, grain yield and grain quality decreased substantially. results revealed that november 20-30 would be the optimum time of sowing for maximum yield with quality seed production of garden pea in bangladesh. introduction the garden pea is grown mainly for young pod to get tender green seeds as vegetable. the mature seeds can be used for preparing dal or chatpati. the crop has gained popularity for its short growth duration and high nutritive value. green pods are rich in vitamins, protein and minerals. besides, a huge amount of garden pea is consumed as soup. garden pea can play an important role to over come our national protein deficit. its demand especially to the urban people is increasing day by day. garden pea is a cool loving crop. it grows well in winter and partly moist climatic condition. an increase in temperature above 20 °c decreases the yield and quality of immature seeds. temperature above 30 °c is harmful for garden pea (sousa-majer et al., 2004). temperature is an important environmental factor that affects the growth of plants in several ways, from root growth, nutrient uptake, and water absorption from the soil, to photosynthesis, respiration, and translocation of photosynthate. sowing at proper time allows sufficient growth and development of a crop to obtain a satisfactory yield because high temperature is one of the major environmental stresses that affect plant growth and development (boyer, 1982). high temperature affects a host of physiological processes, the most relevant of which are respiration, photosynthesis, photosynthate translocation and membrane composition and stability as a result the crop yield decrease (sing, 2006). it was reported that different environmental conditions, especially temperature due to different sowing time provide variable in crop growth, development and yield stability (pandey et al., 1981). so, it is necessary to study the crop growth behaviors in changing climatic condition for future requirement. therefore, the 30 ali et al. present experiment was conducted to evaluate the crop growth pattern, yield and seed quality under different temperature resulted from different sowing time. materials and methods the trial was conducted at the research field of agronomy division, bari, joydebpur, gazipur and ars, burirhat, rangpur during rabi season of 2011-2012 to find out the crop growth pattern, yield and seed quality under different temperature resulted from different sowing time. six sowing dates (10 november, 20 november, 30 november, 10 december, 20 december and 30 december) were evaluated in rcb design with 3 replications. the unit plot size was 3 m x 4 m. garden pea var. bari motorshuti-3 was used in the experiment. fertilizers @ n60p28k40s12 kg/ha were applied in the form of urea, triple super phosphate (tsp), muriate of potash (mop) and zinc sulphate, respectively. all fertilizers were applied as basal. intercultural operations such as weeding, thinning and irrigations were done as and when required. for dry matter estimation and crop growth analysis, 5 plants were sampled at 5 days interval up to maturity. the collected samples were dried component-wise in an oven at 70 °c for 72 hours. the yield component data was taken from 10 randomly selected plants prior to harvest from each plot. at harvest, the yield data was recorded plot wise. the collected data were analyzed statistically and the means were adjusted following lsd test. seed protein content was analyzed by neo infrared analyzer (nir) (da 7200 diode array analyzer). following ista (1999) rules seed quality such as moisture (%) content, seed germination (%) and vigor index (abdul-baki and anderson, 1973) were recorded by the following formulae: % moisture content = 100 x m m m m 12 32   where, m1 = weight in grams of the container and its cover, m2 = weight in grams of the container, its cover and garden pea seed before drying, and m3 = weight in grams of the container, cover and garden pea seed after drying seed germination (%) = 100 x testedseed total germinated seedof no. vigor index (vi) = average seedling dry weight (g) x seed germination (%) leaf area index (lai) = )(m2/m area ground arealeaf 2 results and discussion phenology and crop growth duration was influenced by prevailing temperature variations. november 30 sowing took maximum dura++tion for crop growth (84 days) followed by 20 november (83 days) and 10 november (81 days) and it was 77, 74 and 70 days for 10 december, 20 december and 30 december sowing, respectively. the reasons for variation in growth duration might be due to variation in day/night temperature and increased in temperature at the later sowing curtailed the crop growth duration (table 1a and 1b). 31 effect of sowing time based temperature variations on growth, yield and seed quality of garden pea table 1a. crop phenology and growth duration of gardenpea (bari motorshuti-3) as affected by sowing dates sowing dates emergence (days ) avg. min. tem. 0c at emergenc e stage avg. max. tem. 0c at emergenc e stage duration of vegetativ e stage (days) avg. min. tem. 0c at the vegetativ e stage avg. max. tem. 0c at the vegetativ e stage days to1st flower initiation 10 november 6 19.18 30.92 26 17.40 28.60 27 20 november 6 17.47 29.27 27 15.36 27.02 28 30 november 6 13.58 28.47 26 13.64 25.74 27 10 december 6 15.82 25.75 25 12.81 27.16 26 20 december 6 11.4 25.05 24 12.86 27.53 25 30 december 6 12.3 24.35 22 9.85 22.73 23 table 1b. crop phenology and growth duration of gardenpea (bari motorshuti-3) as affected by sowing dates sowing dates grain growth duration (days) avg. min. tem. 0c in grain growth stage avg. max. tem. 0c in grain growth stage crop growth duration (days) avg. min. tem. 0c in total crop growth duration avg. max. tem. 0c in total crop growth duration 10 november 48 11.96 24.24 81 14.26 25.37 20 november 49 11.05 24.50 83 12.41 25.66 30 november 51 11.13 24.03 84 12.30 25.31 10 december 45 12.16 26.98 77 12.59 26.22 20 december 43 13.17 27.34 74 12.91 26.48 30 december 41 14.16 28.61 70 12.97 26.94 grain growth duration of 30 november, 20 november and 10 november sowings were longer due to low temperatures (min. 11.05 11.13 °c and max 24.03 24.24 °c) prevailed at those time that might prolonged the grain growth period (48-51 days). on the contrary, 30 december and 20 december and 10 december sowings received high temperatures (min. 12.1614.16 °c and max 26.9828.61 °++c) that shorten the grain growth period of bari motorshuti-3 (41-45 days). similar results were observed by gardner (1985), savin and nicolas (1996) who reported that high temperature reduced the length of reproductive period. leaf area index (lai) varied at different sowing dates. lai increased up to 40 dae and thereafter decreased in all the sowing dates (fig.1). irrespective of sowing dates, maximum lai was recorded in 30 november sowing followed by 20 november and 10 november sowings. higher lai indicates better leaf area expansion, which might helped in solar 32 ali et al. radiation interception and efficient utilization of light for more dry matter production. the lowest lai was recorded in 30 december followed by 20 december sowing. fig. 1. effect of sowing dates on leaf area index of bari motorshuti-3 total dry matter (tdm) production increased gradually with the advancement of growth at different sowing dates (fig. 2). tdm of 30 november sowing was higher which was more or less similar with 20 november and 10 november sowing. low temperatures might favor the growth of early sowing (30 november, 20 november and 10 november) that caused higher tdm production. the lowest tdm was found in 30 december sowing followed by 20 december and 10 december sowings. fig. 2. total dry matter of garden pea var. bari motorshuti-3 as influenced by different sowing dates crop growth rate increased up to 40-55 days after emergence of crop then it decreased in all the sowing dates (fig. 3). higher cgr up to 40-55 dae might be due to higher lai. at the later stages of crop growth, declined in cgr caused by mutual shading and leaf senescence which might reduced the photosynthetic efficiency and ultimately reduced the dry matter accumulation rate. similar findings were also observed with different crop species by friend et al. (1962), wall and cartwright (1974), stern and kirby. (1979). 33 effect of sowing time based temperature variations on growth, yield and seed quality of garden pea fig. 3. effect of sowing dates on the crop growth rate of garden pea var. bari motorshuti-3 significant differences were found in plant height, pods/plant, seeds/pod, 1000-seed weight and seed yield/ha due to variation of sowing dates at joydebpur and rangpur (table 2a and 2b). significantly the tallest plant (56.63 cm at joydebpur and 46.3 cm at rangpur), maximum number of pods/plant (17.47 at joydebpur and 15.7, rangpur), seeds/pod (4.47 at joydebpur and 6.0 at rangpur) and highest 1000-seed weights (255.19g at joydebpur) were recorded in 30 november sowing. december 30 sowing gave the shortest plant (36.53 cm at joydebpur and 37.0 cm at rangpur), minimum number of pods/plant (12.19 at joydebpur and 9.3 at rangpur), and seeds/pod (2.91 at joydebpur and 4.0 at rangpur) and lowest 1000-seed weight (203.07g at joydebpur). table 2a. effect of sowing dates on yield components and seed yield of bari motorshuti-3 at bari, joydebpur, gazipur sowing dates plant height (cm) pods/plant (no.) seeds/pod (no.) 1000-seeds/ weight (g) seed yield (t/ha) 10 november 51.97 13.67 4.21 222.14 2.90 20 november 50.63 15.89 4.21 245.16 3.56 30 november 56.63 17.47 4.47 255.19 3.66 10 december 42.63 13.01 3.01 220.22 2.36 20 december 37.33 12.44 3.71 215.66 2.27 30 december 36.53 12.19 2.91 203.07 1.19 lsd(0.05) 5.053 0.91 0.57 10.77 0.38 34 ali et al. cv (%) 6.04 3.55 8.32 2.61 7.78 table 2b. effect of sowing dates on yield components and seed yield of bari motorshuti-3 at ars, burirhat, rangpur sowing dates plant height (cm) pods/plant (no.) seeds/pod (no.) seed yield (t/ha) 10 november 42.0 13.3 4.7 1.98 20 november 45.0 15.7 6.0 2.43 30 november 46.3 15.7 5.3 2.36 10 december 45.7 14.0 4.7 2.03 20 december 39.7 11.0 4.3 1.68 30 december 37.0 9.3 4.0 1.58 lsd(0.05) 5.16 1.10 0.94 0.25 cv (%) 6.66 5.05 8.85 6.91 november 30 sowing received lower day/night temperature that causes longer crop growth duration specially the grain growth period and ultimately more tdm production and translocation of tdm to pods/plant, seeds/pod and 1000-seed weight. on the other hand, 30 december sowing received higher day/night temperature that hastens forced maturity and reduced tdm production and translocation to the yield components. similar results were recorded by peterson and loomis (1949) in kentucky bluegrass, gardner and loomis (1953) in orchard grass, lindsey and peterson (1964) in poa pratensis l. fig.4. maximum and minimum temperature during garden pea (bari motorshuti-3) growing period (2011-2012) at bari, joydebpur, gazipur. 35 effect of sowing time based temperature variations on growth, yield and seed quality of garden pea fig. 4. maximum and minimum temperature during gardenpea (bari motorshuti-3) growing period (2011-2012) at ars, burirhat, rangpur. seed yield is the function of pods/plant, seeds/pod and 1000-seed weight. date of sowing significantly influenced the seed yield/ha of garden pea. november 30 sowing produced the highest seed yield (3.66 t/ha at joydebpur and 2.43 t/ha at rangpur) which was statistically similar with 20 november sowing at both the location. the lowest seed yield (1.19 t/ha at joydebpur and 1.58 t/ha at rangpur) was obtained in 30 december sowing and it was identical with 20 december sowing at the both location joydebpur and rangpur. the highest seed yield at 30 november might be due to maximum number of pods/plant and seeds/pod and highest 1000-seeds weight. this study indicated that raise in temperature reduced the grain growth duration resulted in yield reduction, which is in agreement with the findings of mohanty et al. (2001), bosswell (1926), kruger (1973) and silim et al. (1985). seed quality character also affected significantly due to different dates of sowing. at joydebpur, significantly the lowest moisture content (12.10%), higher germination percentage (97%), maximum vigor index (2.52) and highest protein content (26.51%) was recorded in 30 november sowing. the highest moisture content (12.64%), lower germination percentage (91.33%), minimum vigor index (1.65) and lowest protein content (25.70%) was recorded in 10 december sowing (table 3). table 3. effect of sowing dates on seed quality characters of bari motorshuti-3 sowing dates moisture content (%) germination (%) average seedling dry weight (g) vigor index protein content (%) 10 november 12.43 93.33 0.019 1.79 25.85 20 november 12.38 95.00 0.023 2.19 26.24 30 november 12.10 97.00 0.026 2.52 26.51 10 december 12.49 93.67 0.018 1.69 25.08 20 december 12.59 92.33 0.018 1.66 24.21 30 december 12.64 91.33 0.018 1.64 22.70 lsd(0.05) 0.02 3.28 0.002 0.25 0.41 cv (%) 0.12 1.92 6.60 7.28 0.90 conclusion from this study it might be concluded that november 20-30 would be optimum time of sowing for maximum seed yield and quality seed of garden pea. references abdul-baki, a. a. and j. d. anderson. 1973. vigor determination in soybean seed by multiple criteria. j. crop. sci. 13: 630-633. boswell, v. r. 1926. the influence of temperature upon the growth and yield of garden peas. proceedings of the american soc. hort. sci. 23: 162-168. boyer, j. s. 1982. plant productivity and environmental, science 218: 443-448. 36 ali et al. friend, d. j. c., v. a. helson and j. e. fisher. 1962. leaf growth in marquis wheat, as regulated by temperature, light intensity and day length. can. j. bot. 40: 1299-1310. gardner, f. p. and w. e. loomis. 1953. floral induction and development in orchard grass. plant physiol. 28: 201-217. gardner, f. p., r. b. pearce and r. l. mithchel. 1985. physiology of field crops. the iowa state univ. press, iowa. 50010: 156-186. ista. 1999. international rules for seed testing. seed science and technology. international seed testing association, zurich, switzerland. 27:155-199. kruger, s. n. 1973. effect of time of planting on the seasonal yield of pisum sativum l. qld. j. agric. anim. sci. 30: 25-38. lindsey, k. e. and m. l. peterson. 1964. floral induction and development in poa pratensis l. crop. sci. 4: 540-544. mohanty, s. k., b. baisakih., u. k. dikshit and b. bhol. 2001. kalamung, a promising local mungbean cultivar. environ. ecol. 16(1): 222-223. pandey, b. p., s. k. sirvastava and r. s. lal. 1981. genotype and environment interaction in lentil. lens. 8: 14-17. peterson, m. l. and w. e. loomis. 1949. effect of photoperiod and temperature on growth flowering of kentucky bluegrass. plant physiol. 24: 31-43. savin, r. and m. e. nicolas. 1996. effect of short periods of drought and high temperature on grain growth and starch accumulation of two malting barley cultivars. aust. j. plant physiol. 23: 201-210. silim, s. n., p. d. hebblethwaite and m. c. heath. 1985. comparison of the effects of autum and spring sowing date on growth and yield of combining peas (pisum sativum l). j. agric. sci. 104: 35-46. sing, b. d. 2006. breeding for resistance to temperature stress. plant breeding principle and methods. new delhi, india. 7: 510-511. sousa-majer. m. j., turner. n. c., d. c. hardle., l. r. morton., l. morton and j. v. thomas. 2004. response to water deficit and high temperature of transgenic peas (pisum sativum l.). j. exp. bot. 55(396): 497-505. stern, w. r. and e. j. m. kirby. 1979. primordium initiation at the shoot apex in four contrasting varieties of spring wheat in response to sowing date. j. agric. sci. 93: 203-215. wall, p. c. and p. m. cartwright. 1974. effects of photoperiod, temperature and vernalization on the phenology and spikelet numbers of spring wheats. ann. appl. biol. 76: 299-309. 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.banglajol.info port 443 yield performance of lentil influenced by genotype and inoculant interaction bangladesh agron. j. 2014, 17(1): 41-46 performance of lentil varities as influenced by different rhizobium innoculations m. a. haque1, p. bala2 and a. k. azad2 1lecturer, lakhpur shimulia college, narosindhi 2ph.d. fellow, hajee mohammad danesh science & technology university, dinajpur. corresponding author: kbdpronay@yahoo.com key words: yield, inoculation, lentil abstract a field experiment was conducted at the farm of bangladesh agricultural university, mymensingh during november 2009 to march 2010 to study the response of three lentil varieties (viz., bari masur-1, bari masur-2 and bari masur-3) to rhizobium inoculations to yield. there were three rhizobium inoculants (rhizobium strain bina l 4 , rhizobium strain tal 640, and mixed culture) with uninoculated control and urea @ 50 kg ha-1. phosphorus and potassium @ 26 kg p ha-1from tsp and 33 kg k ha-1 from mp were used as basal. it was observed that rhizobium inoculation alone increased plant height, grain yield and crop residues yield of plant significantly compared to uninoculated control. local inoculants bina l 4 performed better than the exotic culture tal 640 in respect of yield. 50 kg urea ha-1 also recorded better results than control but not superior to any of the inoculation treatments. the highest seed (1,565 kg ha-1) and crop residue yields (3,303 kg ha-1) were recorded from the lentil variety barimasur-3 inoculated with mixed culture. introduction lentil (lens culinaris medik) is one of the most important pulse crops grown in bangladesh. it belongs to the sub-family papilionaceae under the family leguminosae. in bangladesh, it is popularly known as masur. lentil grain contains 25% protein, 0.7% fat, and 59% carbohydrate (afzal et al., 1999). the lentil crop covers 33.33 percent of the total area of pulse in the country (bbs, 2012). total production of lentil in bangladesh, during 2010-2011 was 228568 tons from an area of 180574 hectare with an average yield of 1.2657 t ha-1 (bbs, 2012). pulses are considered as the poor man’s meat as they are the cheapest source of protein for the underprivileged people who cannot afford to buy animal proteins (gowda and kaul, 1982). the stover of the plants together with husk popularly known as bhushi is highly protein concentrated feed for cattle, horse, pig and sheep (tomar et al., 2000). lentil being a legume crop can fix atmospheric nitrogen through root nodules by rhizobium bacteria, which may reduce the pressure of nitrogenous fertilizer application to the crop. it is evident that pulse included in the cropping pattern helped to increase the organic matter in the soil (islam, 1988). seed inoculation with appropriate rhizobium sp is recommended to improve legume growth. they can reduce nitrogenous fertilizer use and protect environment. response to rhizobium inoculation to lentil depends on the soil type, crop cultivars and effectiveness of rhizobium strains. research work on contribution of rhizobium inoculation on growth and yield of lentil is, however, scanty in this country. the selection of strain of rhizobia particularly adapted to specific host plant is important. judicious matching of rhizobium stains with host plants and prudent use of large viable inocula prepared with these organisms is the only way to attain maximum nitrogen fixation and yields of leguminous crops. keeping these in view, the investigation was undertaken to evaluate the effectiveness of three rhizobium inoculants to lentil varieties in respect of yield. materials and methods 42 haque el al. a field experiment was conducted during the winter (rabi) seasons of 2009 -2010 at the farm of the department of soil science, bangladesh agricultural university, mymensingh. the land was situated to the north east side of the farm and situated at latitude of 24.75 ºn and a longitude of 90.50º e. the initial soil sample of the experimental field was collected and analyzed following standard procedures in the laboratory and presented in table 1. table 1. initial soil nutrient status of the experimental field constituents ph oc (%) om (%) total n (%) available p (ppm) exchangeable k (me 100 g-1 soil) ca mg cec experimental field 6.7 1.085 1.875 0.089 11.95 0.12 0.12 3.95 18.50 critical level 2.0 0.1 0.8 14 0.2 14 3.1 0.12 the experiment was laid out in split-plot design having four replications with 3 lentil varieties in main plots and 5 inoculation (no inoculation, bina l4 as a local rhizobium strain, tal 640 as an exotic rhizobium strain, bina l 4 and tal 640 as mixed culture and urea at the rate of 50 kg/ha in sub plots the recommended dose of 26 kg p, 33 kg k was applied as basal. the land was prepared by ploughing and crossploughing with the country plough followed by laddering uniformly. fresh seeds of lentil were dipped in the respective culture broth of 5 days growth for two and half an hours. the seeds were dried in shade. the inoculated seeds of three inoculation treatments were randomly placed in the 5 unit plots of each main plot with spacing of 30 cm using 50 kg seed ha-1 sowing at 22 november, 2009 and harvested at 12 march, 2010. the harvested area of each plot was 4m x 2.5m. the crop was raised following recommended agronomic practices. data on plant height from each plot 5 randomly selected plants were carefully measured and their mean values were determined. the yields were taken plot-wise by harvesting of each plot and then it was converted to hectare basis. the collected data were analyzed statistically using the analysis of variance technique with the help of computer package mstat and mean differences were adjudged by duncan's multiple ranged test (dmrt) (gomez and gomez, 1984). results and discussion plant height the effect of inoculation on plant height (cm), grain yield (kg ha-1), crop residues yield (kg ha-1) and percent yield increase over control are presented in table 2 and table 3. effect of rhizobium inoculation the results showed that the mixedculture gave the highest plant height (11.49 cm) at 40 days of sowing, the percent increase over uninoculated control being 8.8. at 60 days of sowing binal 4 gave highest plants height (18.03 cm) and percent increases over control being 16. at 80 days of sowing recorded the highest plant height (28.32 cm), percent increase over control being 15.26. the maximum plant height (34.30 cm) was produced by mixed culture at 95 days of sowing, which was statistically superior to other treatments. gwal et al. (1995) reported that the rhizobium inoculants when applied resulted in the tallest plants and more branches/plant than the control. similar results were obtained by maurya and sanoria (1986) in chickpea. varietal response at vegetative stage (40 days of sowing), the maximum plant height was produced by the variety bari masur-3 (11.12 cm) followed by barimasur-1 (11.09 cm) and bari masur-2 (10.93 cm). variety bari masur-3 gave tallest plant (16.92 cm) at 60 days of sowing, which was statistically superior to all other varieties. at 80 days of sowing, variety bari masur-2 gave the maximum plant height (27.54 cm) which was statistically similar with bari masur-3 (27.40 cm) but significantly higher than bari masur1 (fig. 2). variety bari masur-3 gave the maximum plant height (33.26 cm) at 95 days of sowing which was statistically similar with bari masur-2 (32.83 cm) but significantly higher than bari masur-1 (31.23 cm) the above results are in agreement with the findings of sattar et al. (1995) who found that 43 rhizobium innoculation in lentil seed inoculation with bradyrhizobium increased plant height of five chickpea cultivars. similar results were obtained by fakir et al. (1988) in pigeonpea. table 2. effect of rhizobium inoculation and variety on seed and hay yield of lentil factor seed yield (kg ha-1) crop residue (kg ha-1) yield increase over control (%) inoculant no inoculated 894d 1,870c rhizobium strain bina l 4 1,163b 2,537b 35.67 rhizobium strain tal 640 1,114b 2,520b 34.76 mixed inoculation 1,309a 2,965a 58.56 urea @50 kg n/ha(u 50 ) 960c 1,915c 2.41 ** ** variety barimasur-1 944c 2,199b barimasur-2 1,044b 2,404ab barimasur-3 1,276a 2,482a ** * in a column, figures having common letter(s) do not differ significantly and those having different letter(s) differ significantly at 5 %(*) and 1% (**) level of significance. table 3. the interaction effect of rhizobium inoculation and variety on plant height, grain yield and hay yield of lentil rhizobium× variety interaction plant height (cm) seed yield (kg ha-1) crop residue (kg ha-1) 40 days 60 days 80 days** 95 days * * v 1 r 0 10.63 15.55 20.95h 30.95 799i 1,784e v 1 r l 11.25 17.50 26.50fg 30.00 1,004e 2,334d v 1 r e 11.10 16.70 25.95g 30.05 979fg 2,309d v 1 r m 11.45 16.40 27.15c-f 33.90 1,118de 2,722bc v 1 u 50 11.00 15.75 26.10g 31.25 821hi 845e v 2 r 0 10.07 15.35 26.65cfg 31.00 858hi 1,954e v 2 r l 11.10 18.00 27.75bcd 33.90 1,107de 2,600c v 2 r e 11.18 16.55 27.85bcd 33.20 1,106de 2,600c v 2 r m 11.45 16.80 28.70ab 34.00 1,243c 2,869b v 2 u 50 10.85 15.45 26.75efg 32.75 906gh 1,995e v 3 r 0 10.98 15.60 26.10g 31.80 1,023ef 1,872e v 3 r l 11.45 18.60 28.00bc 33.00 1,379b 2,675bc v 3 r e 11.25 17.05 27.55cde 33.55 1,256c 2,651bc v 3 r m 11.57 17.30 29.10a 35.00 1,565a 3,303a v 3 u 50 10.35 16.05 26.25fg 32.95 1,154d 1,906e cv (%) 5.80 2.79 4.18 5.65 6.35 in a column, figures having common letter(s) do not differ significantly and those having different letter(s) differ significantly at 5 %(*) and 1% (*) level of significance. r 0 = uninoculated v 1 = bari masur-1 r l = rhizobium strain bina l4 v 2 =bari masur-2 r e = rhizobium strain tal 640 v 3 =bari masur-3 r m = mixed culture of bina l4 and tal 640 u50 = urea @ 50 kg n ha-1 44 haque el al. 0 10 20 30 40 pl an t he ig ht (c m ) no i nocul a te d bi nal 4 tal640 mi xe d u50 inoculant plant height 40das 60das 80das 95das figure 1. effect of rhizobium inoculation (upper) on plant height of lentil plant height 0 5 10 15 20 25 30 35 40 60 80 95 days after sowing pl an t he ig ht (c m ) bari mas ur-1 bari mas ur-2 bari mas ur-3 figure 2. effect of variety on plant height of lentil interaction of rhizobium and variety at 40 days of sowing the highest plant height (11.57 cm) was obtained by the treatment bari masur-3 x mixed culture (v3rm), followed by interaction treatment v 3rl, v 3re, v 2rm, v2re, v 2rl v 1rm, v 1rl, v 1re, v 1 u 50 (bari masur-1 × urea @ 50 kg ha -1) and v 3 r0 (barimasur-3 × uninoculated control) which was statistically similar (table 1). the highest plant height (18.60 cm) was produced by the interaction of v 3rl at 60 days of sowing. the association v 3rm, recorded the highest plant height (29.10 cm) at 80 days of sowing which was statistically superior to all other interaction treatments. the association v 3rm, recorded the highest plant height (35.00 cm) at 95 days of sowing which was statistically superior to all other interaction treatments. the above results are supported with the findings of some investigators. lee and yun (1989) reported on soybean when inoculated with rhizobium stains increased plant height over uninoculated control. similar results were obtained by sattar and ahmed (1995) in mungbean. seed yield 45 rhizobium innoculation in lentil significant positive effect of rhizobium inoculation on seed yield of lentil over noninoculated control was observed (table 2 & table 3). the mixed culture inoculation produced the highest seed yield (1,309 kg ha-1), which was statistically superior to all other treatments, the percent increases (46%) over uninoculated control.. bremer et al. (1990) reported that the rhizobium increased seed yield of lentil by up 135%. namedo et al. (1996) also observed that inoculation increased lentil seed yield by 17.5-23.2% compared with no inoculation. barimasur-3 recorded the highest grain yield (1,276 kg ha-1), which was statistically superior to both varieties. the highest grain yield (1,565 kg ha-1) was recorded from the combination of bari masur-3 with mixed inoculation (v 3rm0), which was statistically superior to all other treatments(table 3). similar results were observed by dziamba and miroslaw (1994) in lentil. crop residue the highest crop residue (2,965 kg ha-1) was recorded in mixed culture, which was significantly superior to all other treatments. it was higher than uninoculated control by 59%. the above results indicated that there was significant beneficial effect of inoculation on crop residue compared to uninoculated control. similar results were also obtained by podder et al. (1989) in lentil. the highest crop residue (2,482 kg ha1) was obtained by the variety bari masur-3, which was statistically superior to bari masur-1 (2,199 kg ha-1) but similar to bari masur-2 (2,404 kg ha-1). similar results were found by islam and afandi (1980) in lentil. the interaction of v 3rm recorded the highest crop residue (3,303 kg ha-1), which was significantly superior to all other treatments. the above results are similar with that of bhuiya et al. (1986). correlation the relationship between total number of nodules at 60 days of sowing and grain yield has been found out. the correlation coefficient (r = 0.6425) was found significant at 1% level of probability. the relation was positive i.e. increase in nodule number results in an increase in the seed yield of lentil. the statistical relationship between total number of nodules at 60 days and crop residues has been calculated and found positive the correlation coefficient (r = 0.858) was highly significant. the statistical relationship between nodule dry weight at 60 days and seed yield has been found positively correlated. the correlation coefficient (r = 0.665) was highly significant. the statistical relationship between total number of nodules at 60 days and crop residues has been found positively correlated. the correlation coefficient (r = 0.858) was highly significant. the statistical relationship b nodule dry weight at 60 days and crop residues has been positively correlated. the correlation coefficient (r = 0.900) was highly significant. the statistical relationship between grain yield and hay yield has been found positively correlated. the correlation coefficient (r = 0.775) was highly significant. conclusion the present investigation suggested that lentil genotype bari masur-3 produced highest seed yield and crop residue. rhizobium strain bina l4 and tal 640 were effective items in term of yield. a significant and positive correlation was observed between nodule number and nodule weight, crop residues and seed yield; nodule weight, crop residue and seed yield. further study is necessary to draw a definite conclusion. references afzal, m. a., m. a. bakr and m. l. rahman. 1999. lentil cultivation in bangladesh. lentil, blackgram and mungbean development pilot project, pulses research station, bari, gazipur-1701. 46 haque el al. bbs. 2012. yearbook of agricultural statistics of bangladesh. bangladesh bureau of statistics, ministry of planning, government of the people’s republic of bangladesh, dhaka. bhuiya, z. h., m. r. islam, m. j. uddin and m. s. hoque.1986. performance of some rhizobium inoculations on blackgram (vigna mungo). bangladesh j. agric. 11(4): 55-63. bremer, e., c. kessel, l. nelson, r. j. rennie, d. a. rennie and c. van-kessel. 1990. selection of rhizobium leguminosarum strains for lentil (lens culinaris) under growth room and field conditions. plant soil. 121(1): 47-56. dziamba, s. and h. microslaw.1994. effect of inoculating lentil seeds with rhizobium strains on yield. biuletyn instytutu hodowli-i aklimatyzacji roslin. no. 189, 85-90:11. fakir, m. s. a., a. a. a. mushi and s. m. m. alam. 1998. effects of rhizobium inoculation, nitrogen and phosphorus on yield contributing characters of soybean. bangladesh j. agril. sci. 15(2): 211-215. gomez, k. a. and a. a. gomez. 1984. statistical procedures for agric. res. 2nd edn. john willey and sons. new york. pp.207-215. gowda, c. l. l. and a. k. kaul. 1982. pulses in bangladesh, bari publication. 6 (1): 27-29. gwal, h. b., r. j. tiwari and d. k. gupta. 1995. fertilizer management of lentil under rainfed conditions in madhya prodesh. lens newsl. 22(1-2): 11-12. islam, r. and f. afandi. 1980. response of lentil cultivars to of rhizobium inoculation and nitrogen fertilization. lens. 7: 50-51. islam, m. s. 1988. nutrient status of bangladesh soils. annual report for 1988. bangladesh agril. res. inst., gazipur, bangladesh. pp.82-85. lee, h. s. and s. h. yun. 1989. studies on the response of rhizobium inoculation and nitrogen concentration on growth and yield of soybean cultivars. korean j. crop sci. 34(4): 400-407. maurya, b. r. and c. l. sanoria. 1986. beneficial effects of coinoculating chickpea seed with rhizobium , azotobacter and pseudomonas . indian j. agric. sci. 56(6): 463-466. namdeo, s. l., s. c. gupta and r. k. joshi. 1996. influence of rhizobial inoculation on nodulation and yield of lentil genotypes under rain fed conditions. lens newsletter. 23(1& 2): 24-26. podder, a. k., m. a. sattar and g. marshed. 1989. performance studies of some isolated native rhizobial inocula on the production and nodulation of lentil with or without nitrogen fertilizer. proc. 6 th natl. bot. conf., jan. 18-19. abs. no. 43, p.23. podder, a. k. 1994. performance of single and mixed rhizobial inoculafor nodulation and growth of lentil. lens newsl. 21 (1): 39-40. sattar m. a., m. a. quader and s. k. a. danso. 1995. nodulation, nitrogen fixation and yield of chickpea as influenced by host cultivar and bradyrhizobium stain differences. soil biol. biochem. 27 (4/5): 725727. sattar, m. a. and s. u. ahmed. 1995. response of mungbean (vigna radiata l. wilczek) to inoculation with bradyrhizobium as affected by phosphorus levels. proc. intl. cong. comm. iv. pp.419-423. tomar, s. k., p. tripathi and a. l. rajput. 2000. effect of genotype, seeding method and diammonium phosphate on yield and protein and nutrient uptake of lentil (lens culinaris l. medik). indian j. agron. 45 (1): 148-152. critical period of weed competition in transplant aus rice cv bangladesh agron. j. 2014, 17(1): 95-102 critical period of weed competition in transplant aus rice cv. brri dhan27 under non-saline agro-ecosystem m. t. rahman, s. ahmed, n. j. lipi, m. h. rashid and m. i. hoque1 department of agronomy, patuakhali science and technology university, patuakhali, bangladesh, 1department of environmental science, bangladesh agricultural university, mymensingh, bangladesh corresponding author: trahman302@gmail.com key words: critical period, weed competition, transplant aus, brri dhan27 abstract a study was conducted to determine the critical period of weed competition in transplant aus rice for var. brri dhan27. among the treatments, weed free condition, competition of weed for first 10, 20, 30, 40, 50, 60 and 70 days and weed free later on, unweeded condition, one weeding at 20 days after transplanting and one weeding at 40 days after transplanting, the unweeded control plots showed the poor performance result in case of maximum parameters where grain yield was reduced the highest percentage (38.54%). on the basis of cost benefit ratio it was observed that the critical period of crop weed competition extended up to 30 days after transplanting of aus var. brri dhan27. introduction rice is one of the most important staple foods for more than half of the world’s population (irri, 2006) and influences the livelihoods and economies of several billion people. in asia, more than 80% of the people live on rice, and their primary food security is entirely dependent on the volume of rice produced in this part of the world (kabir, 2006). it is estimated that 40% of more rice production will be required by 2030 to satisfy growing demand with no increases in cropping areas (khush, 2005). weeds are at present the major biotic constraint to increase rice production world wide (zhang, 1996). about 33% of this loses are caused due to weeds alone (mukherjee and singh, 2005). the yield losses due to uncontrolled weed growth in lowland and upland rice ranged from 12 to 81% (chopra and chopra, 2003; mukherjee and singh, 2005). normally the loss in rice yield ranges between 15-20% yet in severe cases the yield losses can be more than 50% depending upon the species and intensity of weeds (brri, 2006). to develop a comprehensive control program for the weed, it is important to know its critical period of competition in transplant rice. the critical period of weed competition depends on several factors like species of weed, life time duration of crops, climatic factors, crop species, environmental factors etc. critical period of weed control is an integral part of integrated weed management (iwm) and can be considered the first step to design weed control strategy (anonymous, 2003). in general critical period of crop weed competition is throughout in direct seeding situation and in transplanted it vary from 15 to 45 days (singh and bhan, 1988). the most critical period for competition between rice and weeds is when the rice is in the vegetative phase and the yield components of rice are being differentiated (mukherjee and singh, 2003). though critical period of weed–crop competition is an important component of weed management technology package for any crop but for aus variety brri dhan27 it has not been investigated to find out the critical period of weed competition in transplant aus rice cv. brri dhan27. materials and methods 96 rahman et al. the study was conducted at the field laboratory of the department of agronomy, patuakhali science and technology university, patuakhali during the period of april to august 2012. geographically, the patuakhali science and technology university is situated at 20°20″ n latitude and 90°20″ e longitude. it belongs to the agro ecological zone (aez)-13 named ganges tidal flood plain. the experimental site was about 1.5 m above the sea level. the field of the experimental site was characterized by non calcareous grey floodplain soil with silty clays. it was well drained and medium high. the soil was mildly alkaline, non-saline, loam in texture and having soil ph ranges from 5.50 to 6.50. organic matter content was low (1.1%) (srdi, 2005). the experiment was laid out in a randomized complete block design with three replications and eleven treatments as: t1 = weed free condition, t2 = competition of weed for first 10 days and weed free later on, t3 = competition of weed for first 20 days and weed free later on, t4 = competition of weed for first 30 days and weed free later on, t5 = competition of weed for first 40 days and weed free later on, t6 = competition of weed for first 50 days and weed free later on, t7 = competition of weed for first 60 days and weed free later on, t 8 = competition of weed for first 70 days and weed free later on, t 9 = unweeded condition, t10 = one weeding at 20 days after transplanting (dat) and t11 = one weeding at 40 dat. the area of a unit plot was 4 m × 2.5 m. the sprouted seeds were sown in the prepared seed beds on 5th april, 2012. the seedlings were transplanted in the main field @ 2 seedlings hill-1 with 20cm × 15 cm spacing on 30th april, 2012. fertilizers were applied @ 168 g urea, 60 g tsp, 30 g mop, 17 g gypsum and 5 g znso 4 to the plots. the whole amount of fertilizers except n was applied before final land preparation. urea was top dressed @ 56 g in three equal splits at 15, 30 and 45 days after transplanting. proper crop protection measures were taken during the entire course of crop production. weeds were collected at every 10 days interval according to the treatments mentioned. number of weed plant of each species in the unit plot was counted with the help of a plant counter. the intensity of infestation of each species of weed was calculated as the number of weed stands per unit area divided by the number of hills per unit area. three weed sample plot1 were collected at the time of weeding. the plant counter was placed at random in the unit plot and all the weeds within each 1 m2 were uprooted, dried first in the sun and thereafter, 24 hours in an electric oven maintaining a constant 1050 c. after drying weeds weight of each sample was measured and expressed in g m-2. three weed sample plot-1 were collected at the time of harvesting. the crop of all plots was harvested on 3 july 2012. crop and yield contributing were also recorded. results and discussion seven species of weeds under four different families were found in the experimental field. three species belonged to the family cyperaceae, two from gramineae and one from each of onagraceae and pontederiaceae (table 1). among those weed species, cyperus difformis l., jussiaea decurrens (watt.) dc. cynodon dactylon (l.) pers. were predominated, and constituted about 84% of the total weed vegetation. only cyperus difformis l. constituted 63.82 percent of total weed infestation and it was followed by jussiaea decurrens (watt.) dc. (11.40 percent). in total 14.26 weeds competed against one hill of rice of which 10.16 belonged to the family cyperaceae, 1.88 belonged to the gramineae family and rest small portion was belonging to other two family. thirteen types of weeds were found in direct seeded and transplanted aus rice as affected by method of planting and weeding regime by sarker et al. (2002). individually the highest intensity of weed infestation (9.09 hill-1) was recorded in cyperus difformis l. fimbristylis miliacea (l.) vahl. showed the lowest intensity and numerically it was only 0.38 weeds hill-1. jussiaea decurrens (watt.) dc. and cynodon dactylon (l.) pers. was produced in an intensity of 1.63 and 1.22 weeds hill-1. in case of weed population per square meter space total 456 weeds were found m-2 and the highest and lowest number of weeds belonged to the family cyperus difformis l. and fimbristylis miliacea (l.) vahl. respectively as percent of total weed vegetation and intensity of weed infestation at weeding. in a study ahmed et al. (1986) found that the principal weeds were monochlora vaginalis, scirpus mucrontus and cyperus iria in case of br3 cultivation in aus season. in another study in case of direct seeded upland rice cultivation cyperus rotundus and echinochloa crusgalli 97 critical period of weed competition in transplant aus rice was the principal weed (mamun et al., 1986). mercado (1979) found that competition of echinochloa crusgalli was found to be the highest at a density of 20 plants m-2 within the critical period of crop-weed competition. this difference might be due to climatic change, varietal change and other cultural management. table 1. infested weed species and their population in transplant aus rice cv. brri dhan27 name of weeds family weed populatio n m-2 % of total weed intensity of weed (hill-1) local name english name scientific name sobuj nakful green flatsedge cyperus difformis l. cyperaceae 291 63.82 9.09 pani morich winged water primorse jussiaea decurrens (watt.) dc. onagraceae 52 11.40 1.63 durba bermuda grass cynodon dactylon (l.) pers. gramineae 39 8.55 1.22 chechra bog bulrush scirpus mucronatus l. cyperaceae 22 4.82 0.69 chela sheand grass parapholis incurve l. gramineae 21 4.61 0.66 soto panikochu pickerel weed monochria vaginalis (burm. f.) presl. potedariaceae 19 4.17 0.59 joina globe fringerush fimbristylis miliacea (l.) vahl. cyperaceae 12 2.63 0.38 the weed population increased gradually from the competition of weed for first 10 to 60 days and weed free later on. the highest (598.00) weed population was found in t7 (competition of weed for first 60 days and weed free later on) and the lowest one (77.00) was found in t 2 ( for first 10 days and weed free later on). during harvesting time no weed was found in the experimental plot as the plots were kept weed free after every weeding treatment (table 2). the highest (498.30) number of weeds were found in the plots which were kept unweeded (t9) and the lowest (288.70) was found in t 11 (one weeding at 40 dat). all the treatments had significant effect on weeds dry weight m-2 at weeding. treatment t7 produced the highest (254.20 g) weeds dry weight at weeding whereas t2 produced the lowest (6.54 g). the treatments t9 and t10 gave the highest (204.20 g) and the lowest (144.30 g) dry weight of weeds. similar result was found by sarker et al. (2002). on average 33.8% weed dry weight was reduced due to competition from aus rice (karim, 2000). table 2. effect of duration of weed competition on the population and dry matter production of weeds in cultivation of transplant aus rice cv. brri dhan27 treatments weeds population (m-2) weeds dry weight (m-2) at weeding at harvest at weeding at harvest t1 0.00j 0.00d 0.00 i 0.00d t2 77.00 i 0.00d 6.54h 0.00d t3 152.00h 0.00d 7.69h 0.00d t4 218.00g 0.00d 51.84f 0.00d t5 361.00d 0.00d 147.30e 0.00d 98 rahman et al. t6 415.00b 0.00d 168.60b 0.00 d t7 598.00a 0.00d 254.20a 0.00d t8 398.00c 0.00d 162.90c 0.00d t9 0.00 j 498.30a 0.00 i 204.20a t10 287.00f 311.70b 48.31g 144.30c t11 332.00e 288.70c 158.40d 165.20b lsd (0.05) 0.69 1.55 3.19 2.94 different treatments had significant effect on the plant height of transplant aus rice cv. brri dhan27. numerically the plots which were kept weed free for whole the cultivation period (t 1) gave the highest (138.8 cm) plant height and it was followed (136.1 cm) by 10 days for weed competition. on the other hand, the plots which were allowed for competition of weed for first 60 and 70 days; and the plots which were weeded only once at 40 days after transplanting (dat) gave the lower plant height than others (fig. 1). perera et al. (1992) and sultana (2000) also found similar reduction on rice plant height due to competition of e. crusgalli. fig. 1. effect of duration of weed competition on plant height of transplant aus rice cv. brri dhan27 (lsd (0.05) = 4.67) all the plots except those were kept unweeded (t9) for the entire cultivation period showed statistically at par in terms of panicle length. treatments t1 to t4 produced higher panicle length than others where the longest (24.14 cm) panicle was produced where kept weed free throughout the cropping period (t1). the plots in which first weeding were done after 40, 50, 60 and 70 days after transplanting and unweeded throughout the cropping period gave lower number of total tillers than others (table 3). table 3. effect of duration of weed competition on the yield contributing characters of transplant aus rice cv. brri dhan27 treatments panicle length (cm) total tillers hill-1 (no.) filled grains panicle-1 (no.) unfilled grains panicle-1 (no.) 1000-grain weight (g) t1 24.14a 11.09a 108.0a 16.72a 31.55a t2 23.90ab 10.75a 104.7ab 14.46b 31.55a t3 23.77abc 10.82a 101.4bc 10.56d 31.58a t4 23.10bcd 9.557b 98.13c 14.60b 31.22ab t5 22.84cde 8.837c 98.54c 9.493e 31.54a t6 22.61def 8.820c 92.11d 16.49a 31.00abc 99 critical period of weed competition in transplant aus rice t7 22.24def 8.297cd 84.40e 10.46d 30.77bcd t8 21.65f 8.543cd 78.31f 12.25c 30.46cd t9 19.14g 8.003d 74.42g 14.26b 30.15d t10 22.04ef 9.647b 84.84e 7.710f 30.73bcd t11 21.90ef 9.650b 86.75e 14.60b 30.53cd lsd (0.05) 1.01 0.65 3.56 0.64 0.66 the plots which were kept weed free throughout the whole cultivation period, and the plots in which first weeding were done at 10, 20, and 30 dat i.e. t1 to t4 gave statistically higher number (9.865–10.37) of effective tillers (fig. 2). fig. 2. effect of critical period of rice weeds competition on effective tillers hill1 of transplant aus rice cv. brri dhan27 (lsd (0.05) = 0.80) the highest (108.00) number of filled grains panicle-1 was recorded from the plots which were kept weed free for the total cropping duration. plots which were weeded for the first time at 20 dat and kept weed free for later on (t3) showed the highest 1000grain weight (31.58 g). the plots which were weeded only once at 20 and 40 dat (t 10 and t11) showed similar effect (3.29 and 3. 28 t ha -1) in terms of grain yield of brri dhan27. percent grain yield reduction was increased with the increasing of weed competition period and it reached to the highest as 34.54% in unweeded control plots. in case of one weeding, weeding at 20 and 40 days after transplanting reduced the grain yield of about 17% of that of the weeded control plots. weed free plots and the plots in which the competition of weed were allowed for first 10, 20, 30 days and kept weed free for later on gave higher yield than others. grain yield of t. aus rice cv. brri dhan27 was significantly affected by the treatments of weeding. the plots which were kept weed free from transplanting to harvesting gave the highest (3.97 t ha-1) grain yield and it was followed (3.94 t ha-1) by t2 .the unwedded plots gave the lowest (2.44 t ha -1) yield and it was followed by treatments (table 4). when weed infestation is increased, the rice plants deprive from nutrient and other environmental components. as a result, the long time weed infested plot showed lower performance than short time weed infestation. table 4. effect of duration of weed competition on the yield of transplant aus rice cv. brri dhan27 treatments grain yield straw yield t ha-1 % reduction t ha-1 % reduction t1 3.97 a 3.22 ab t2 3.94 a 0.76 3.36 a -4.25 100 rahman et al. t3 3.90 a 1.76 3.22 ab 0.00 t4 3.89 ab 2.02 3.09 ab 4.04 t5 3.76 b 5.29 2.86 bc 11.18 t6 3.50 c 11.84 2.65 cd 17.70 t7 3.05 e 23.17 2.53 cd 21.43 t8 2.49 f 37.28 2.34 d 27.33 t9 2.44 f 38.54 2.42 d 24.84 t10 3.29 d 17.13 2.65 cd 17.70 t11 3.28 d 17.38 2.57 cd 20.19 lsd (0.05) 0.13 0.42 weed population and their dry weight was increasing with the increasing of weed competition duration and weed removal delayed up to 60 days after transplanting and decreased thereafter. it might be due to death of some older weeds and thinning of newly germinated weeds. unweeded control plots showed the poor result in case of maximum parameter where the grain yield reduced in the highest percentage (38.54%). in case of grain and straw yield the plots which were allowed for 10 days weed competition (t2) showed the highest performance. treatment t2 gave better plant height (136.1), panicle length (23.90) and effective tillers hill-1 (10.13). on the other hand the plots in which competition of weed was allowed for first 20 days showed better performance in terms of total tillers hill-1 (10.82). in case of grain yield t1 (control), t2 (competition of weed for 10 days), t 3 (competition of weed for 20 days) and t4 (competition of weed for 30 days) gave same and higher (3.89 – 3. 97 t ha-1) yield than others. conclusion the result obtained from the study showed that the percentage of grain yield reduction with the increasing of crop weed competition was negligible up to 30 days competition. so, crop weed competition for first 30 days could be a critical period in transplant aus rice cv. brri dhan27. references ahmed, s., a. mamun, a. m. a. islam and s. m. a. hossain. 1986. critical period of weed competition in transplanted aus rice. agric. rev. 27: 247257. ahmed, s. and a. majid. 1977. effect of weed control duration on paddy yield of different varieties. j. agric. res. 15: 293-298. anonymous. 2003. principles of weed management. international rice research institute, p.o. box.983. manila, philippines. p.113. baloch, m. s., i. u. awan, s. a. jatoi, i. hussain and b. u. khan. 2000. evaluation of seeding densities in broadcast wet seeded rice. j. pure appl. sci. 19: 63-65. brri (bangladesh rice research institute). 2006. weed identification and management in rice. bangladesh rice res. inst. joydebpur, gazipur, bangladesh. pp.101-113. burnside, o. c., m. l. wiens, b. j. holder, s. weisberg, e. a. ristau, m. m. johnson and j. h. cameron. 1998. critical period for weed control in dry beans (phaseolus vulgaris). weed sci. 46: 301-306. chopra, n. k. and n. chopra. 2003. weed management strategy in rice a review. indian j. weed sci. 35: 27-29. 101 critical period of weed competition in transplant aus rice garrity, d. p., m. morillion and k. moody. 1992. differential weed suppression ability in upland rice cultivars. agron. j. 84: 586-591. irri (international rice research institute). 2006. bringing hope, improving lives: strategic plan 2007–2015. manila, philippines. p.61. jennings, p. r. and r. c. aquino. 1968. studies on weed competition in rice. ii. the mechanism of competition among phenotypes. evolution. 22: 529-542. johnson, d. e. 2002. weed management in small holder rice production in the tropics. chatham, kent, uk: natural resources institute, university of greenwich. kabir, h. 2006. adaptation and adoption of the system of rice intensification in myanmar using the farmer field school (ffs) approach. available: http://ciifad.cornell.edu/sri/theses/kabirthesis. pdf. karim, s. m. r. 2000. competitive ability of three grass weeds grown in upland direct-seeded rice in bangladesh. pakistan j. agric. res. 16: 24-27. khush, g. s. 2005. what it will take to feed 5.0 billion rice consumers in 2030. plant mol. biol. 59: 1-6. mamun, a. a., s. ahmad and a. u. sarker. 1986. critical period of crop weed competition in direct-seeded aus rice. bangladesh j. agric. sci. 13: 61-66. mercado, b. l. 1979. introduction to weed science. southeast asian regional center for graduate study and research in agriculture, laguna, philippines. p.292. mukherjee, d. and r. p. singh. 2003. in: proc. biennial conf. of indian soc. weed sci. held at pant nagar from 12-14, march, p.11. mukherjee, d. and r. p. singh. 2005. weed management strategy in rice. indian j. agron. 50: 194-196. perera, k. k., p. g. ayres and h. p. m. gunasena. 1992. root growth and the relative importance of root and shoot competition in the interactions between rice (oryza sativa) and e. crusgalli. weed res. 32: 6776. sarker, m. y., m. m, hossain, m. k. hasan, m. a. h. khan, m. r. amin and f. begum. 2002. weed infestation in direct seeded and transplanted aus rice as affected by method of planting and weeding regime. j. biol. sci. 2: 652-655. singh, o. p. and v. m. bhan. 1988. chemical weed control in lowland transplanted rice under puddle condition. indian j. weed sci. 18: 244-249. srdi (soil resource development institute). 2005. upozilla nirdeshika: dumki (in bengali). 2nd edn. dhaka, bangladesh. pp.7-87. sultana, r. 2000. competitive ability of wet seeded boro rice against e. crusgalli and e. colonum. m. s. thesis bau, mymensingh, bangladesh. pp. 36-50. zhang, ze-pu. 1996. weed management in transplanted rice. in: b. a. auld and k. u. kim (eds.) weed management in rice. fao plant production and protection paper 139. food and agriculture organization of the united nations, rome, italy. http://ciifad.cornell.edu/sri/theses/kabirthesis http://ascidatabase.com/author.php?author=m.y.%20sarker&last= http://ascidatabase.com/author.php?author=m.%20mosaddeque%20hossain&last= http://ascidatabase.com/author.php?author=m.k.%20hasan&last= http://ascidatabase.com/author.php?author=m.a.h.%20khan&last= http://ascidatabase.com/author.php?author=m.r.%20amin&last= http://ascidatabase.com/author.php?author=f.%20begum&last= bangladesh agron. j. 2014, 17(1): 59-66 source-sink manipulation and population density effects on fodder and grain yield of hybrid maize shah-al-emran, k. m. s. haque, q. a. khaliq and m. y. miah1 department of agronomy,1 department of soil science, bangabandhu sheikh mujibur rahman agricultural university, gazipur1706, bangladesh corresponding author: s.emran@cgiar.com key words: source-sink, fodder, hybrid maize and bcr abstract an experiment was carried out in the field laboratory at the bangabandhu sheikh mujibur rahman agricultural university, gazipur, bangladesh, during rabi season of 2009-2010. planting material was maize var. bari hybrid maize 7.three levels of population density (66667, 83333 and 111111 plants ha-1) and four source-sink manipulation, viz. removed all leaf blades below the lower most cob, removed tassel and all leaf blades below the lower most cob, removed all leaf blades except those adjacent to cob and no clipping, were imposed at silking stage. during crop growth, removal of all leaf blades below the cob showed less adverse effect on grain yield and yield parameters and the leaves so removed can be used as green fodder. removal of tassel and all leaf blades except those adjacent to cob showed adverse effect on grain yield and yield parameters. complete defoliation severely reduced grains on cob. the highest gross return and benefit cost ratio (bcr) was obtained from the treatment having 1,11,111 plants ha-1 with no clipping while the lowest from the treatment with removal of all leaf blades excluding those adjacent to cob in 66667 plants ha-1. in case of dual purpose, 1,11,111 plants ha-1 with removal of tassel and all leaf blades below the lower most cob gave the highest gross return but 66667 plants ha-1 with removal of all leaf blades below the lower most cob gave the highest bcr (1.78) introduction maize (zea mays) is a major crop used as food, feed, fuel and a source of carbohydrate, oil, protein and fiber. dry-matter production and grain yield are limited by the source–sink affiliation of crop assimilates and the end nutrient availability in the grain is expected to be constrained by the sink capacity as well as by the contribution of source (zhang et al., 2012).various ways of leaf clipping have influences on dry matter accumulation and grain yield. it was reported that tassel clipping two days after silking, generally increases the grain yield at 6.7 percent more than the control due to increased grain weight (wang, 1996). leaf clipping of upper three leaves at 2 and 16days after tasseling, decreases grain yield by 24 and 9 percent, respectively (wang, 1996). when leaf clipping done at the primary stage of grain development, the grain yield decrease would arise due to increased grain number (wang, 1996). leaf clipping at early season significantly reduces both the stem length and leaf area; however, it did not have any effect on leaf emergence. also, leaf clipping at early season decreased soluble grain carbohydrate in order to devote the carbohydrates for vegetative growth and reduce sucrose sources (prioul and dugue, 1992). it was noticed that when the defoliation was severe and its time was closer to silking stage, forage yield and soluble sugars decreased greatly (burton, 2004). the effect of leaf defoliation on canopy photosynthesis and changing the sink and source carbohydrates showed that soluble sugars in plants with leaf clipped (control, above ear leaf clipping, below ear leaf clipping and full leaf clipping at flowering stage) was different (egile, 2000). it was observed that full leaf clipping treatment made the most decrement of canopy photosynthesis and changing the sink and source carbohydrates and the percentage of soluble sugar in different parts of plant such as grains (egile, 2000). the grains of plants which had limitation on their sinks were not able to use possible carbohydrates (burton, 2004). cultivar and leaf clipping treatments had significant effects on grain yield, 60 emran et al. globulin, glutenin, prolamine, albumin and soluble carbohydrates. the grain yield is mostly observed in above ear leaf clipping treatment which is followed by ear leaf clipping and below ear leaf defoliation. grain yield is a function of dry mass production and harvest index. yield is mostly related with its dry matter production ability. for a genotype, generally the higher the dry matter accumulation, the greater is the yield under favorable condition. however, there is little information on the interaction between leaf clipping and planting density to grain and fodder yield of maize. this study was undertaken to elucidate the effect of different levels of leaf clipping and population density on grain yield and yield attributing characters and green fodder yield of maize. materials and methods a field experiment was conducted in research field of bangabandhu sheikh mujibur rahman agricultural university (latitude: 24° 09' n., longitude: 90° 25’ e., and 8.4 meters above sea level) in winter 2009-10, to study the relations between source-sink manipulation and population density in corn plants. the soil of the experimental site was silty clay loam (clay of 35.6%, sand of 17.2%, and silt of 47.2%) with ph 5.6, and organic carbon of 0.65%. the experiment was conducted in a randomized complete block design with three replications. a total of three population densities viz. 66,667 (75 cm x 20 cm), 83,333 (60 cm x 20 cm) and 1,11111 (60 cm x 15 cm) plants ha-1 and four leaf & tassel clippings were used in this experiment. among the clipping treatments, no clipping was treated as control (c1), with other three levels, i.e. removal of all leaf blades below the lowermost cob (c2), removal of tassel and all leaf blades below the lowermost cob (c 3) and removal of all leaf blades except those adjacent to cob (c4). the seeds of bari hybrid maize-7 were planted by maintaining different population density, as mentioned above, and clipping treatments were applied during silking stage of plant growth. the sourcesink manipulation treatments were imposed by removing the designated source organs with scissors after silking stage. leaf area was measured, at 7 days intervals throughout the growth period by an automatic leaf area meter immediately after leaf clipping. three plants were randomly collected from each unit plot and all the green leaves were taken for measuring leaf area by a leaf area meter (model amm-8, hayashi dehnko co. ltd., tokyo, japan). leaf area index was calculated by using the following formula collected been haveleaves thefrom where area ground leaves allof arealeaf of thesum lai = the data on yields and yield contributing characters of maize varieties and soil parameters were statistically analyzed by “mstatc” software to examine the significant variation of the results due to different treatments. the treatment means were compared by lsd at 5% level of significance. results and discussion cob length cob length varied significantly among the plant population grown at different densities and clipping levels (table 1). length of cob decreased significantly with the increasing level of population density. the plants grown at the lower density (66667 plants ha-1) produced the longest cob (154.7 mm) where leaf blades were removed below the lower most cobs. however, no significant reduction was recorded in cob length in other clipping treatment in same density. in contrast, the lowest cob length (119.3 mm) was 61 sourch-sink manipulation and population density of hybrid maize found in plants grown at 1,11,111 plants ha-1 and removed the tassel and all leaf blades below the lowermost cob. similar finding was reported by osorio (1976), loesch et al. (1976) and rathore et al. (1976). cob diameter the data pertaining to cob diameter as influenced by plant density, levels of defoliation and their interactions are presented in table 1. significant differences in cob diameter were noticed due to plant density and levels of defoliation. maximum cob diameter (46.36 mm) was recorded in treatments where all leaf blades below the lowermost cob were removed with 66,667 plants ha-1. however, minimum cob diameter (39.04 mm) was recorded in 1,11,111 plants ha-1 where tassel and all leaf blades below the lowermost cob were removed. number of grains per cob significant variations were observed in number of grains per cob in all plant densities and clipping levels (table 1). however, increasing level of clipping decreased the number of grains per cob. a gradual reduction in number of grains per cob with increasing the level of clipping was observed. among the treatments, the highest number of grains per cob (406) was recorded at the density of 66,667 plants ha-1 with no clipping (c1). however, no significant difference in grain numbers was found in other clipping treatments except 66667 plants ha-1. on the other hand, the lowest grains per cob were found in 1,11,111 plants ha-1with removal of all leaf blades except those adjacent to cob. statistically similar result was also found in removal of tassel and all leaf blades below the lower most cobs. in 83,333 plants ha-1, clipping treatments gave statistically similar result except removal of all leaf blades except those adjacent to cob which gave lower grains per cob than other clipping treatments. similar finding was reported by rathore et al. (1976). 100-grain weight 100 grain weight of maize was subjective to different density levels (table 1). however, increasing level of clipping decreased the 100-grain weight, even, within same density level. a gradual reduction in 100grain weight per treatment with the increasing level of clipping was also observed among the plant densities. it was recorded that tested hybrid maize produced the highest 100-grain weight (28.79 g) in 83333 plants ha-1 with no clipping (d 2c1). however, the lowest 100-grain weight (24.49 g) was found in same density with removal of all leaf blades except those adjacent to cob. grain yield grain yield is the product of number of plant ha-1, cobs plant-1, grains cob-1 and individual grain weight. clipping treatment, at all density levels, there was a large impact on grain yield of maize (table 1) revealed that the grain yield significantly increased with the increasing level of density and decreased due to clipping. grain yield increased up to 7.9 t ha-1 in 1,11,111 plants ha-1 with no clipping (d 3c1) and thereafter decreased with the interaction in density and clipping levels. except 1,11,111 plants ha-1 with no clipping and those three, all treatment was statistically similar. only 83333 plants ha-1 with removal of all leaf blades except those adjacent to cob, 1,11,111 plants ha-1 with removal of all leaf blades except those adjacent to cob and 66667 plants ha-1 with removal of all leaf blades except those adjacent to cob produced less than 5.21 t ha-1 grain where all other treatments produced more than 5.9 t ha-1 grain yield with a central tendency of 6.5 t ha-1 grain yield. furthermore, the yield increment was mainly owing to improvement in yield attributing characters at higher leaf present. in 1,111,11 plants ha-1 with no clipping, lai was significantly highest and the number of plant as well as cob ha-1 showed same result. increased grain yield under increasing level of leaf present might have increased in photosynthetic capacity due to increase in photosynthetic leaf surface, chlorophyll content, leaf longevity and partitioning of more accumulated dry mass from source to sink, favorable growth and nutrient uptake resulted hence produced higher grain yield. plants grew healthy and produced long size of cobs with bold 62 emran et al. and heavy grains in 66667 plants ha-1density. the results of present study can be favorably compared with those of hassen (2003), zewdu (2003), li-xiangjun et al. (2005) and chaudhary et al. (2005). narayanaswamy et al. (1994) and simeonov and tsankova (1990) also reported similar result. in contrast, vivas et al. (1988) reported that plant density was not a critical factor in determining maize yield. table 1. yield attributes of three population densities grown under four different clipping levels treatment combination cob length (mm) cob diameter (mm) grains cob-1 (no.) 100-grain weight (g) grain yield (t ha-1) harvest index (%) d 1 c 1 152.5 45.91 406.0 28.56 6.572 45.75 d 1 c 2 154.7 46.36 401.2 27.90 6.232 54.18 d 1 c 3 148.9 45.89 371.5 27.70 5.927 51.50 d 1 c 4 141.1 43.67 304.3 25.46 4.238 39.66 d 2 c 1 141.6 43.99 331.2 28.79 6.486 44.17 d 2 c 2 135.1 42.98 302.9 27.48 6.149 50.79 d 2 c 3 134.8 44.48 308.5 28.05 6.323 59.14 d 2 c 4 132.1 42.58 280.3 24.49 4.695 44.73 d 3 c 1 131.3 43.30 314.3 28.41 7.906 48.06 d 3 c 2 123.3 40.25 272.1 27.13 6.478 51.06 d 3 c 3 119.3 39.04 213.9 25.90 6.536 52.03 d 3 c 4 120.9 39.66 195.6 26.45 5.206 48.97 lsd (0.05) 11.13 2.314 45.37 1.604 0.9473 8.288 cv (%) 4.82 3.16 8.69 3.48 9.23 9.95 d 1 = (75 cm x 20 cm ), 66667 plants ha-1 c 1 = control (no clipping was done) d 2 = (60 cm x 20 cm ), 83333 plants ha-1 c 2 = removal of all leaf blades below the lowermost cob d 3 = (60 cm x 15 cm ), 111111 plants ha-1 c 3 = removal of tassel and all leaf blades below the lowermost cob c 4 = removal of all leaf blades except those adjacent to cob the price of maize grain and fodder: tk. kg-1 12.50 and 2.5 harvest index the ratio of economic yield to biological yield is termed as harvest index. the highest harvest index (59.14%) was found in 83,333 plants ha-1 with removal of tassel and all leaf blades below the lower most cob treatment (table 2). the lowest hi (39.66%) was recorded in 66667 plants ha-1 with removal of all leaf blades except those adjacent to cob treatment with no clipping, 83333 plants ha-1. correlation analysis relationship between plant density and dependent variables correlation analysis evinces that cob length (r = -0.82), cob diameter (r = -0.745), number of grain per cob (r = -0.74), grain weight per cob (r = -0.67), total dry matter content (r = -0.69), light transmission rate before clipping (r = -0.685) had negative and significant (1%) relationship with crop density but none of the parameters exhibits significant positive relationship with crop density (table 2). this may be due to the struggle created by plant density. closer planting creates competition for nutrients and all other growth factors. grain yield showed affirmative but insignificant relationship with plant density might be that the number of cob increases with number of plant. the finding is consistent with the findings of osorio (1976), rathore et al. (1976), hsu and huang (1984) and loesch et al. (1976). relationship between leaf clipping and dependent variables 63 sourch-sink manipulation and population density of hybrid maize the computed pearson’s product moment correlation co-efficient at 5% level of probability implies that number of grain per cob (r = -0.48), grain weight per cob (r = -0.55), 100-grain weight (r = -0.71), grain yield (r = -0.71), total dry matter production (r = -0.67) and leaf area index (r = -0.91) maintained negative significant relationship with leaf clipping (table 2). the results confirms with the results of previous findings of zelitch (1982), chaudhary et al. (2005) and hassen (2003). the reason behind such type of relationship might be due to the fact that leaf clipping increases light transmission ratio and total photosynthetic activity may be reduced. on the other hand light transmission rate after clipping (r = 0.8) maintained positive significant relationship with leaf clipping. table 2. relationship between plant components with different treatment variables as influenced by leaf clipping and plant density cob length cob diameter no. of grain cob-1 grain wt. cob-1 100 grain wt. grain yield fodder yield total dry matter leaf area index light transmission ratio density -.823** -.745** -.742** -.674** -.116 .300 .243 -.686** .161 -.075 clipping -.305 -.306 -.482** -.549** -.710** -.713** .905** -.672** -.905** .805** cob length 1 .901** .897** .883** .387* .177 -.479** .787** .148 -.167 cob diameter 1 .869** .844** .421* .240 -.512** .735** .168 -.203 no.of grain cob-1 1 .907** .397* .297 -.643** .843** .311 -.353* grain wt. cob-1 1 .584** .485** -.703** .879** .401* -.532** 100 grain wt. 1 .588** -.696** .611** .645** -.687** grain yield 1 -.654** .322 .723** -.753** fodder yield 1 -.799** -.866** .773** total dry matter 1 .581** -.495** leaf area index 1 -.702** light transmission ratio 1 *indicates significant at 5% level ;**indicates significant at 1% level economic analysis the highest gross return and benefit cost ratio (bcr) was obtained from the treatment having 1,11,111 plants ha-1 with no clipping (tk. 98819 ha-1, bcr 1.78) while the lowest from the treatment with removal of all leaf blades except those adjacent to cob in 66,667 plants ha-1 (tk. 63604 ha-1, bcr 1.22) (table 3). in case of dual purpose,1,11,111 plants ha-1 with removal of tassel and all leaf blades below the lowermost cob gave the highest gross return (tk. 89520 ha-1) but 66667 plants ha-1 with removal of all leaf blades below the lowermost cob gave the highest bcr (1.6). table 3. yield and return of maize var.bari hybridmaize-7 production in three population densities grown under four different clipping levels treatment combination cost (tk.) fodder yield (t ha-1) grain yield (t ha-1) return from fodder (tk*) return from grain (tk.) gross return (tk.) bcr d 1 c 1 50387 0.00 6.57 0.00 82147 82147 1.63 d 1 c 2 51657 1.905 6.23 4763 77894 82657 1.6 d 1 c 3 52005 1.905 5.93 4763 74086 78849 1.52 d 1 c 4 52145 4.250 4.24 10627 52978 63605 1.22 d 2 c 1 52434 0.00 6.49 0.00 81080 81080 1.55 d 2 c 2 53755 2.397 6.15 5992 76862 82854 1.54 64 emran et al. d 2 c 3 54342 2.397 6.32 5992 79033 85025 1.56 d 2 c 4 54501 4.627 4.69 11567 58686 70253 1.29 d 3 c 1 55489 0.00 7.91 0.00 98820 98820 1.78 d 3 c 2 56338 3.127 6.48 7817 80976 88793 1.57 d 3 c 3 56867 3.127 6.54 7817 81704 89521 1.57 d 3 c 4 57265 6.258 5.21 15644 65080 80724 1.41 lsd (0.05) 0.9473 11840 0.2 cv (%) 9.23 8.53 7.87 d 1 = (75 cm x 20 cm), 66667 plants ha-1 c 1 = control (no clipping was done) d 2 = (60 cm x 20 cm), 83333 plants ha-1 c 2 = removal of all leaf blades below the lowermost cob d 3 = (60 cm x 15 cm), 111111 plants ha-1 c 3 = removal of tassel and all leaf blades below the lowermost cob c 4 = removal of all leaf blades except those adjacent to cob *75tk = 1 usd (approximately) conclusion grain yield increased up to 20% if no clipping was done with 1,11,111 plants ha-1, however, with the same density and removal of all leaf blades produced the highest fodder yield. the highest grain yield loss (35.5 %) was observed in 66,667 plants ha-1 with removal of all leaf blades, except those adjacent to cob. the highest gross return and bcr was obtained from 1,11,111 plants ha-1 with no clipping (tk. 98820 ha-1 and 1.78) and the lowest from 66667 plants ha-1 with removal of all leaf blades except those are adjacent to cob (tk. 63605 ha-1 and 1.22). in case of both grain and fodder yield, the combination of 1,11,111 plants ha-1 with removal of tassel and all leaf blades below the lowermost cob gave the highest gross return (tk. 89521 ha-1) but 66,667 plants ha-1 with removal of all leaf blades below the lowermost cob gave the highest bcr (1.6). references ahmad, n. and f. c. muhammad. 1999. plant density effect on yield and quality of maize seed. j. agric. res. 37 (1): 25-29. barthakur, b. c., s. nath and p. k. purkayastha. 1975. effect of dates of sowing, rates of nitrogen and planting densities on grain yield of hybrid maize ganga 11. indian j. agron. 20(3): 257-259. burton, w. j. 2004. effects of defoliation on seed protein concentration in normal and high protein lines of soybean. crop sci. 72: 131139. chaudhary, a. n., m. i. latif, haroon, m. ur-rasheed and g. jilani. 2005, profitability increase in maize production through fertilizer management and defoliation under rain fed cropping. int. j. of bio.and biotech., 2(4): 1007-1012. desiderio, e., l. cuocolo, g. mariani and m. monotti. 1989. effects of sowing date and plant density on yields of maize of different maturity groups. (in italian). informatore-agrario. 45(14): 57-69. egile, d. b. 2000. variation in leaf starch and sink limitations during seed filling in soybean. crop sci. 39: 1361-1368. hassen, h. 2003. effect of defoliation on yield components of maize and under sown forage. agri. topica, 18(1/2): 5-7. 65 sourch-sink manipulation and population density of hybrid maize hsu, a. n. and s.c. huang. 1984. effects of plant density on yield and agronomic characteristics of maize in spring and autumn cropping seasons. bull. taichung district agril. improv. sta. pub. no. 9. pp.13-21. kolcar, f. and z. videnovic. 1988. effect of time of planting and plant density on the grain yield of some zp hybrid of maize fao maturity group 200. arhiv-za-poljopri-vredne-nauke (yugoslavia) 49 (176): 309-320. li-xiangjun, s. anpinginanaga, a. e. enejj and a. m. ali. 2005. mechanisms promoting recovery from defoliation in determinate and indeterminate soybean cultivar. j. food agric. env.3(3/4):178-183. loesch, p. j. j., c.f. stark and m. s. zuber. 1976. effects of plant density on the quality of cobs used for corn cob pipes. crop sci. 16(5): 706-709. madhavan, m. v., s. shanmuegasundaram and s. p. palaniappar. 1986. effect of population on physiological growth parameters of pigeon pea genotypes in sole and inter cropped stand with sorghum co. 22. j. agron. crop sci. 157(1): 43-61. mostert, a. j. and j. n. marais. 1982. the effect of detasselling on the yield of irrigated maize. crop prod. 11: 163-167. mrityunjoy, b., i. m. ahmed, m. asaduzzaman and w. sultana. 2008. performance of intercropping grain maize with triticale and grasspea as forage crops. intl. j. sustain. crop prod. 3(6): 34-37. narayanaswamy, m. r., v. veerabadran, c. joyanthi and c. chinnuswammy. 1994. plant density and nutrient management for rainfed maize in red soil. madras agril. j. 81(5): 248-251. osorio, f.o. 1976. population effects on yield and other characteristics of maize in the e-1 zamorano valley, honduras. field crop abst. 33(2): 126-1980. rathore, d. m., k. singh and b. p. singh. 1976. effect of nitrogen and plant population on the yield attributes of maize. indian j. agric. res. 10(2): 7 9 8 2 . sabir, m. r., s. a. h. shah, m. a. shahzad and i. ahmed. 2001. effect of plant population on yield and yield components of maize. j. agric. res. 39(2): 125-129. sawhney, j. s., s. s. bhinder, m. s. sidhu and r. s. narang. 1989. agronomic practices for higher productivity in winter maize. indian j. agron. 34(1): 24-26. simenov, n. and g. tsankova. 1990. effect of fertilizers and plant density on yield of maize hybrids with two years. (in bularian). rasteniev’dni-nauki 27(8): 14-18. sufian, m. a. and m. z. abedin. 1985. effect of plant population and plants per hill on the growth and yield of sweet corn. bangladesh j. agri. 10(2): 17-22. tano, f., m. r. mannino and f. aiello. 1987. row spacing and plant density of grain maize (part two). (in italian). informatore-agrario. 43(26): 59-61. vasic, g., krzic. and d. budimirovic. 1988. effect of late planting on maize yield under irrigation. savremenapoljoprivreda (yugoslavia) 36(11-12): 506-516. vivas, h., r. moresco and s. gambaudo. 1988. effects of nitrogen and plant density on maize production in eastern argentina. turrialba 38(2): 127-131. wang, o. q. 1996. effects of altered source sink ratio on canopy photosynthetic rate and yield of maize. photosynthetica. 32: 271-267. wipo. 2006. improved grain quality through altered expression of seed proteins. pub. no.: wo/2006/071219. http://www.wipo.int/pctdb/en/ zelitch, i. 1982. the close relation between net photosynthesis and crop yield. bio-sci. 32: 796-802. zewdu, t. 2003. effect of defoliation and intercropping with forage legumes on maize yield and forage production. trop. sci. 43(4): 204-207. http://www.wipo.int/pctdb/en/ 66 emran et al. 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.banglajol.info port 443 genotypic differences in soybean in relation to growth and ions accumulation under nacl salinity and water stress conditions bangladesh agron. j. 2014, 17(1): 47-58 genotypic differences in growth and ions accumulation in soybean under nacl salinity and water stress conditions m. s. a. khan1, m. a. karim2 and m. m. haque2 1agronomy division, bari 2department of agronomy, bsmrau corresponding author: shawquatshahadat@yahoo.com key words: salt and water stress, dry matter production, ions accumulation abstract salt and water stress tolerance of the seven soybean genotypes viz. bari soybean 6, bd 2329, bd 2342, ags 95, bgh 02026, galarsum and bd 2331 were evaluated for their performance at 0 and 100 mm nacl under well watered & water stress (watering with 70% depletion of available water at wilting) conditions at the banghabandhu sheikh mujibur rahman agricultural university, salna, gazipur. the results indicated that all the growth parameters like plant height, shoot dry weight, root dry weight and dry matter distribution in different plant parts of the genotypes sharply decreased when the plants were exposed to water stress, salt stress and, combined salt and water stress conditions. among the genotypes reduction in dry matter production was the least in galarsum and bd 2331 in both the salt stress and, the combined salt and water stress conditions. these genotypes also accumulated lower amount of na+ and higher amount of k+ in leaf tissues under salt stress and, combined salt and water stress environments as compared to others. introduction soybean is classified as a moderately salt-tolerant crop and the yield will be reduced when soil salinity exceeds 5 ds m-1 (maas and hoffman, 1977). high levels of salts in the soil can often cause serious limitations to crop production. raptan et al. (2001) found that salinity decreased root, stem and leaf dry weights, and reduced plant height of mungbean plants. the adverse effect of salinity on plant is dependent on salt concentration in the substrate, duration of exposure to salinity and stages of plant growth (blum, 1988; maas and poss, 1989; gill, 1990). it is well known that salinity harms crop growth. plants under high saline conditions cannot always absorb sufficient water for metabolic activities or maintain turgidity because of the low osmotic potential in the growth media. at the same time, plants absorb damaging amounts of na and cl (blum, 1988; greenway and munns, 1980; karim et al., 1992). na+ is the primary cause of ion specific damage, resulting due to a range of disorders in enzyme activation and protein synthesis (tester and davenport, 2003). therefore, exclusion of na+ at root level and maintenance of high k+ at shoot level are vital for the plants to grow under saline conditions (munns et al., 2000; tester and davenport, 2003). it is very common in the arid and semi-arid regions that when the crop growth season progresses, the precipitation decreases, and temperature and evapo-transpiration increase, resulting in rising salt concentration in the soil solution (abdulrahman and williams, 1981). thus, salt and water stress prevails at the same time in the dry seasons, which very often add extra harm on plant growth (karim et al., 1993). normally, salinity stress produces high osmotic potential in the soil solution (hayward and spurr, 1943), whereas water stress impairs soil moisture transmission due to matric potential (gingrich and russell, 1957). however, the adverse effects of both salt and water stress are primarily due to the restriction of water uptake by the roots (karim et al., 1993). the response of soybean to salinity stress depends both on genotypes and environmental conditions (ghassemi-golezani et al., 2009). 48 khan et al. in the coastal area of bangladesh, soil salinity increases during dry period (march – may) due to lack of rainfall. thus, salinity and drought exist together during that particular period. it is well known that salinity exerts more deleterious effects on plant growth when drought prevails along with salinity. therefore, this study was undertaken to analyze the growth and mineral ions accumulation pattern in some soybean genotypes. materials and methods the experiment was conducted in a plastic house of the department of agronomy at banghabandhu sheikh mujibur rahman agricultural university (bsmrau), salna, gazipur, bangladesh. seven genotypes (bari soybean 6, bd 2329, bd 2342, ags 95, bgh 02026, galarsum and bd 2331) of soybean including barisoybean 6 were used for testing their salt and water stress tolerance. selected genotypes were denoted as moderately salt tolerant (khan, 2013). seeds were washed several times in the tap water for surface cleaning then sown in the soil medium on january 13, 2011 in plastic pots having 30 cm in height and 24 cm inner diameter. each pot contained 12 kg air dried sandy loam soil. chemical fertilizers of 0.30 g urea, 0.90 g tsp, 0.60 g mop and 0.60 g gypsum per pot were also incorporated into the soil before sowing. the pots were watered daily for easy germination. after the emergence and establishment, three uniform healthy seedlings per pot were allowed to grow for three weeks (21 dae) in equal environment. after three weeks of emergence, all the genotypes were divided into 6 groups. the treatment groups were; control (t 1), water shortage (irrigated with 70% depletion of available soil water when wilting sign developed) from 21 dae (t2), 50 mm nacl irrigated from 21 dae (t 3), 50 mm nacl irrigated from 21 dae + water shortage from 35 dae (t4), 100 mm nacl irrigated from 21 dae dae (t5) and 100 mm nacl + water shortage from 35 dae (t 6). the control groups of plants were irrigated with tap water only. the experiment was arranged in two factors completely randomized design (crd) with 8 replications. plant samples were collected in 42 dae and different plant parts were separated and then oven dried at 70 ºc for 4 days to measure the dry weight. dried leaves were finely ground and the samples were dry-ashed at 500 ºc for 8 hours and then digested with concentrated hydrochloric acid. na and k concentrations were determined by a flame spectrophotometer. data were analyzed by mstat-c program and the treatment means were compared by using least significant difference (lsd). results and discussion plant height plant height of soybean genotypes significantly decreased under water stress, salt stress and their combination (fig. 1). under only water stress condition, significantly the tallest plant recorded in bari soybean 6 and the shortest in bd 2331 genotype. plant height was affected more in combined salt and water stress conditions than only in salt stress conditions in both the salinity levels (50 and 100 mm nacl), though the reduction was higher at higher salinity levels. at higher salinity (100 mm nacl), the tallest plant was recorded in ags 95 (26.13 cm) followed by bd 2342 (25.63 cm) and the shortest in galarsum (22.47 cm). at higher salinity (100 mm nacl) combined with water stress condition, the tallest plant recorded in bd 2342 (25.23 cm) followed by bgh02026 (25.13 cm), while the shortest in bd 2329 (20.10 cm). the reduction of plant height was also more in higher salinity both in only salt stress and, combined salt and water stress conditions (fig. 2). at higher salinity, the maximum relative plant height was recorded in bd 2331 (97.70%) followed by ags 95 (95.82 %) and the lowest in bd 2329 (75.95 %). but at higher salinity combined with water stress condition, the highest relative plant height recorded in ags 95 (87.28 %) followed by galarsum (86.84 %) and the lowest relative plant height in bd 2329 (67.75%). salt stress and water deficit significantly affected the plant height of soybean which is in agreement with ozturk et al. (2004); sari and ceylan (2002). osmotic potential of soil decreased due to salt water, and matric potential decreased due to water shortage in soil, which made interruption in water 49 genotypic differences in soybean under nacl salinity and water stress uptake by the plant resulting in reduction of shoot growth, is commonly expressed by stunted shoot growth. genotypic difference in the reduction of plant height due to salinity were also reported earlier by aziz et al. (2005); sultana et al. (2009) and padder et al. (2012) in mungbean, mannan et al. (2012) in soybean. 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 soybean genotypes pl an t h ei gh t ( cm ) cont ws 50mm nacl 50mm+ws 100mm nacl 100mm+ws here, cont = control, ws = water stress, mm = nacl concentration. fig.1. plant height of soybean genotypes as affected by salinity and water stress, and their combination at 42 dae 0 20 40 60 80 100 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 soybean genotypes r el at iv e he ig ht (% ) cont ws 50mm nacl 50mm+ws 100mm nacl 100mm+ws here, cont = control, ws = water stress, mm = nacl concentration. fig. 2. relative plant height of soybean genotypes as affected by salinity and water stress, and their combination at 42 dae shoot dry weight shoot dry weight of soybean genotypes sharply decreased when plants were exposed to water stress, salt stress and, combined salt and water stress (fig. 3). under only water stress conditions, bd 2342 produced the highest shoot dry weight (1.94 g) followed by bari soybean 6 (1.87 g), and the least recorded in bd 2331 (1.03 g). shoot dry weight was affected more in the combined salt and water stress conditions than only in the salt stress in both the salinity levels (50 and 100 mm nacl). but the reduction was higher in higher salinity levels. at higher salinity (100 mm nacl), the highest shoot dry weight recorded in bd 2342 (1.89 g) followed by bari soybean 6 (1.75 g) and the lowest in bgh 02026 (1.18 g). at the higher salinity combined with water stress condition, the highest shoot dry weight recorded in by bari soybean 50 khan et al. 6 (1.64 g), which was followed by bd 2342 (1.63 g) and the lowest recorded in bgh 02026 (1.18 g). the relative shoot dry weight of soybean reduced in water stress, salt stress and, combined salt and water stress conditions (fig. 4). under only water stress condition, the highest relative shoot dry weight recorded in bari soybean 6 (77.5 %) followed by galarsum (76.7 %) and the lowest in ags 95 (39.7 %). the relative shoot dry weight was reduced more in the combined salt and water stress conditions than only salt stress in both the salinity levels. at higher salinity (100 mm nacl), the highest relative shoot dry weight was recorded in galarsum (79.9 %) followed by bd 2331 (77.9 %) and the lowest in bd 2329 (50.2 %). but at higher salinity combined with water stress condition, the highest relative shoot dry weight wasrecorded in galarsum (68.4 %) followed by bari soybean 6 (68.0 %) and the lowest recorded in bd 2329 (44.1%). 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 soybean genotypes sh oo t d ry w eig ht (g /p lan t) cont ws 50mm nacl 50mm+ws 100mm nacl 100mm+ws here, cont = control, ws = water stress, mm = nacl concentration. fig. 3. shoot dry weight of soybean genotypes as affected by salinity and water stress, and their combination at 42 dae 0.0 20.0 40.0 60.0 80.0 100.0 120.0 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 soybean genotypes re lat ive sh oo t d ry w eig ht (% ) cont ws 50mm nacl 50mm+ws 100mm nacl 100mm+ws here, cont = control, ws = water stress, mm = nacl concentration. fig. 4. relative shoot dry weight of soybean genotypes as affected by salinity and water stress, and their combination at 42 dae wang et al. (2011) also reported that total biomass, shoot biomass, leaf biomass decreased significantly in saltcedar (tamarix chinensis) seedlings due to water scarcity under salt and water stress condition. under only water stress, when soil dries up, the matric potential decreases, therefore increases the resistance of water flow to the roots in a non-linear fashion (homaee et al., 2002). application of salt water increases in soil salinity. at given salt water content, the soil water potential reduces but does not reduce water flow to the roots. root cortical cells can osmotic ally adjust to some extent allowing water to readily move into the root. therefore, shoot dry weight of soybean was affected more in combined salt and water stress conditions than only in salt stress conditions. the finding is also in agreement with the findings of meiri (1984) that the matric potential preferentially affected the shoot growth of bean more than did the osmotic potential. 51 genotypic differences in soybean under nacl salinity and water stress under salt stress condition, cell expansion is reduced due to low turgor, beside these excess sodium ion damages cell membrane and organelles, resulting in plant growth reduction. the reduction in shoot dry weight due to salinity was reported by karim et al. (1993) in triticale, khan et al. (1997) in rice, aziz et al. (2005) in mungbean, waheed et al. (2006) in pigeonpea, jamil et al. (2007) in sugarbeet, sultana et al. (2009) in mungbean, chookhampaeng (2011) in pepper plant and mannan et al. (2012) in soybean. root dry weight root dry weight of soybean genotypes decreased under water stress, salt stress and, combined salt and water stress condition (fig. 5). under water stress, the highest root dry weight (0.30 g) was recorded in bgh02026 and the lowest (0.10 g) in bd 2342. root dry weight affected more in combined salt and water stress than only in salt stress in both the salinity levels (50 and 100 mm nacl). at higher level of salinity, the highest root dry weight (0.31 g)was recorded in both bd 2342 and bd 2331, and the lowest in bgh02026 (0.21 g). at higher level of salinity combined with water stress condition, the highest root dry weight (0.24 g) was recorded in both bd 2342 and ags 95 genotypes, and the lowest in bd 2331(0.19 g). the relative root dry weight reduced in water stress, salt stress and, combined salt and water stress conditions (fig. 6). the relative root dry weight was reduced more in combined salt and water stress conditions than only salt stress in both the salinity levels (50 and 100 mm nacl). at higher level of salt stress condition, the highest relative root dry weight recorded in galarsum (88.4 %) which was followed by bd 2331 (74.6 %) and the lowest recorded in bd 2329 (49.4%). at higher level of salt combined with water stress condition, the highest root dry weight also recorded in galarsum (69.8 %), which was followed by bgh02026 (61.1%) and the lowest recorded in bd 2329 (42.4 %). 0.00 0.10 0.20 0.30 0.40 0.50 0.60 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 soybean genotypes ro ot d ry w ei gh t ( g/ pl an t) cont ws 50mm nacl 50mm+ws 100mm nacl 100mm+ws here, cont = control, ws = water stress, mm = nacl concentration. fig. 5. root dry weight of soybean genotypes as affected by salinity and water stress, and their combination at 42 dae 0.0 20.0 40.0 60.0 80.0 100.0 120.0 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 soybean genotypes re la tiv e ro ot d ry w ei gh t ( % ) cont ws 50mm nacl 50mm+ws 100mm nacl 100mm+ws 52 khan et al. here, cont = control, ws = water stress, mm = nacl concentration. fig. 6. relative root dry weight of soybean genotypes as affected by salinity and water stress, and their combination at 42 dae under salt and water stress condition, cell expansion is reduced due to low turgor, beside these excess sodium ion damages cell membrane and organelles, resulting in reduction of root growth. wang et al (2011) reported that root biomass decreased significantly in tamarisk seedlings due to water severity under salt and water stress condition. decreased in radical dry weight of mungbean under salinity and water stress was also reported by padder et al. (2012). the reduction in root dry weight due to salinity were reported by aziz et al. (2005); sultana et al. (2009) in mungbean, waheed et al. (2006) in pigeonpea, jamil et al. (2007) in sugarbeet and chookhampaeng (2011) in pepper plant. dry matter distribution dry matter distribution in different plant parts of soybean genotypes as affected by water stress, salt stress and, combined salt and water stress condition is presented in fig. 7. all plant parts were reduced by stresses. under water stress, the highest stem in bari soybean 6 (0.77 g), petiole (0.25 g) and leaves (0.95 g) in bd 2342 were recorded while the lowest stem (0.36 g), petiole (0.14 g) and leaves (0.53 g) were recorded in bd 2331. all plant parts reduced more in all genotypes in the combined salt and water stress than only in the salt stress in both the salinity levels (50 mm and 100 mm nacl). but the reduction was more in leaves than stem and petiole. at higher salinity, the highest leaves dry weight recorded in bd 2342 (0.93 g), which was followed by bd 2329 (0.92 g) and the lowest recorded in bgh02026 (0.71 g). but at higher level of salinity combined with water stress condition, the highest leaves dry weight recorded in bd 2329 (0.81 g) and the lowest (0.59 g) in bgh 02026. under water stress condition, cell expansion of leaf is reduced due to low turgor, which is controlled by the processes related to cellular water uptake and cell wall extension (cramer and bowman, 1993). therefore, leaf area was decreased resulted in decreased leaves dry weight under salt and water stress condition. long term exposure to salinity lead to premature leaf senescence; and thus reduced the photosynthetic area (cramer et al., 1991) in soybean plants. the highest reduction of leaf dry weight in the genotype bgh02026 at 100 mm nacl salinity might be due to high salt load in the leaf. the salt that exceeds the capacity of compartmentation in the cell vacuoles of leaf causing salt to build up in the cytoplasm to toxic levels (munns, 2002; munns et al., 2006). the reduction in leaf dry weight due to salinity was reported by karim et al. (1993) in triticale, khan et al. (1997) in rice, aziz et al. (2005) in mungbean and mannan et al. (2013) in soybean. 0.0 1.0 2.0 3.0 4.0 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 genotypes d ry m at te r ( g/ pl an t) stem petiol leaf pods control water stress 53 genotypic differences in soybean under nacl salinity and water stress 0.0 1.0 2.0 3.0 4.0 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 genotypes d ry m at te r ( g/ pl an t) stem petiol leaf pods 0.0 1.0 2.0 3.0 4.0 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 bari soy 6 bd 2329 bd 2342 ags 95 bgh02026 galarsum bd 2331 genotypes d ry m at te r ( g/ pl an t) stem petiol leaf pods here, cont = control, ws = water stress, mm = nacl concentration fig. 7. dry matter accumulation in different plant parts of soybean genotypes as affected by salinity and water stress, and their combination at 42 dae sodium accumulation sodium (na) uptake in leaf tissue (%) of soybean genotypes was significantly affected by water stress, salt stress and, combined salt and water stress condition (table 1). the accumulation of na was lower in leaves of all the genotypes under water stress than control. significantly the lowest na content was found in bd 2329 (0.072 %), which was identical with bari soybean 6 (0.091 %) in only water stress treatment. the accumulation of na was more in the salt stress than in the combined salt and water stress conditions in both the salinity levels (50 and 100 mm nacl). results reveal that concentration of na increased with increasing salinity levels. genotypic differences were also observed in na accumulation. at higher level of salt stress (100 mm nacl), galarsum (0.223%) accumulated significantly the lowest concentration of na, which was identical by the accumulation of bd 2331 (0.226 %) and the highest was accumulated by bgh 02026 (0.495%). at higher level of salinity combined with water stress condition, galarsum (0.173%) was also accumulated lower amounts of na which was at par with the accumulation of bd 2331 (0.182%) and the highest in ags 95 (0.330 %).the results are in agreement with the earlier reports that tolerant genotypes accumulate lower amount of na than the salt sensitive ones (karim et al., 1992; khan et al., 1997; ahmadi et al., 2009; mannan et al., 2013). kao et al. (2006) also reported that differences among soybean species in leaf accumulation of na+ might be responsible for the differential sensitivity to nacl treatments. plant responses to salt and water stress have much in common phenomenon. salinity leads to many metabolic changes identical to those caused by water stress, and there are still salt-specific effects. accumulation of na+ in leaves results in necrosis and premature leaf senescence (munns, 2002). 50 mm nacl 50 mm nacl + ws 100 mm nacl 100 mm nacl + ws 54 khan et al. table 1. sodium (na) uptake in leaf tissue (%) of soybean genotypes as affected by salinity and water stress genotypes control water stress (ws) 50 mm nacl 50 mm nacl + ws 100 mm nacl 100 mm nacl + ws bari soy-6 0.136 0.091 0.319 0.179 0.390 0.226 bd 2329 0.083 0.072 0.275 0.195 0.330 0.198 bd 2342 0.143 0.121 0.283 0.217 0.358 0.303 ags 95 0.162 0.094 0.286 0.239 0.385 0.330 bgh 02026 0.165 0.143 0.413 0.253 0.495 0.292 galarsum 0.132 0.105 0.160 0.138 0.223 0.173 bd 2331 0.105 0.094 0.162 0.143 0.226 0.181 lsd (0.01) 0.022 cv (%) 4.98 potassium accumulation accumulation of potassium (k) in leaf tissue (%) of soybean genotypes was also affected by water stress, salt stress and, combined salt and water stress condition (table 2). the accumulation of k was higher in leaves under water stress than control. under only water stress treatment, significantly the highest k content was found in bd 2331 (2.52 %), which was identical by the accumulation of bd 2342 (2.42 %) and the lowest in ags 95 (1.96 %). the accumulation of k was more in the combined salt and water stress than in the salt stress conditions in both the salinity levels (50 and 100 mm nacl) in all the genotypes, except bari soybean 6 and bgh 02026. the accumulation of k decreased with increasing salinity levels. at higher level of salt stress (100 mm nacl), galarsum (1.75 %) accumulated significantly the highest amounts of k which was identical by the accumulation of ags 95 (1.70 %), bd 2331 (1.70 %) and bari soybean 6 (1.65 %). the least amount of k was accumulated by bd 2342 (1.55 %) at this level of salinity. at higher level of salinity combined with water stress condition, galarsum (1.80 %) also accumulated significantly the highest amounts of k, which was identical by the accumulation of bd 2331 (1.75 %), ags 95 (1.75 %) and bd 2329 (1.70 %), while bgh 02026 (1.34 %) accumulated the least.under water stress as well as under salt stress conditions, k plays an important role in osmoregulation, and stress tolerant genotypes accumulate higher amounts of k than susceptible ones (blum, 1988; qadar, 1988). here, soybean genotype galarsum accumulated higher amount of k in leaves than others under the salt and water stress conditions. a greater degree of salt tolerance in plants was found to be associated with a more efficient system for selective uptake of k over na (neill et al., 2002). the selective uptake of k in contrast to na is considered as one of the important physiological mechanisms contributing to salt tolerance in many plant species (poustini and siosemardeh, 2004). there was a negative relationship between na and k concentration in leaves. similar results had been observed by khan et al. (1997) and goudarzi and pakniyat (2008). table 2. potassium (k) uptake in leaf tissue (%) of soybean genotypes as affected by salinity and water stress genotypes control water stress (ws) 50 mm nacl 50 mm nacl + ws 100 mm nacl 100 mm nacl + ws bari soy-6 1.96 2.16 2.06 1.56 1.65 1.44 bd 2329 2.06 2.37 1.96 2.11 1.56 1.70 bd 2342 2.37 2.42 1.75 1.96 1.55 1.65 ags 95 1.75 1.96 1.80 1.85 1.70 1.75 bgh 02026 2.16 2.22 2.01 2.06 1.56 1.34 galarsum 1.85 2.16 1.96 2.06 1.75 1.80 bd 2331 1.70 2.52 2.16 2.16 1.70 1.75 55 genotypic differences in soybean under nacl salinity and water stress lsd (0.01) 0.15 cv (%) 3.74 conclusion the results of this study indicated that all the growth characters of the soybean genotypes sharply decreased when plants were exposed to water stress, salt stress and, combined salt and water stress conditions. variation in salt and water stress tolerance of soybean genotypes was obvious. among the genotypes, reduction in dry matter production was least in galarsum and 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on germination, growth, yield, ionic balance and solute composition of pigeon pea (cajanus cajan l. millsp). pakistan j. bot. 38(4): 1103-1117. wang, wei, r. wang, y. yuan, n. du and w. guo. 2011. effects of salt and water stress on plant biomass and photosynthetic characteristics of tamarisk (tamarix chinensis lour.) seedlings. afr. j. biotechnol. 10(78): 17981-89. long-term bed planting trial for enhancing sustainable crop production in drought prone areas bangladesh agron. j. 2014, 17(1): 23-32 long-term bed planting effect on stabilizing productivity of rice and wheat in a drought prone area of bangladesh m. ilias hossain1, m. i. hossain2, m. r. i mondal3, m. k. sultan4, m. gathala5 and t. p tiwary5 1 senior scientific officer (agronomy), 2principal scientific officer (agril. engg.), 3director general and 4 director (research) of bangladesh agricultural research institute, gazipur and 5cropping system agronomists, cimmyt bangladesh corresponding author: iliasrwrc@gmail.com key words: bed planting, cropping system, productivity, sustainable, drought abstract the systems productivity, soil fertility and n use efficiency were evaluated in a drought area of rajshahi under five n fertilizer levels (0, 40, 80, 100 and 120 % n of the recommended dose, two straw retention (sr) (0 and 30%) and two tillage options [raised bed and conventional tillage (ct)] in a long term bed planting experiment with rice-wheat (rw) systems. the findings revealed that the permanent raised beds (prb) with 30% straw retention had the highest productivity for all the three crops in the sequence. within each n rate the total system (ricewheat-mungbean) productivity was higher with 30% sr on prb and the least in ct with 0 % sr. at 80 % of recommended fertilizer n rate, mean annual system productivity was 12.8 t ha-1 for prb with 30% sr, 11.2 t ha-1 with prb on 0% sr and 10.3 t ha-1 with ct without straw. n uptake and use efficiency increased with increasing n levels with bed planting up to 120% n application (120 kg n ha-1) in wheat, both 100% (80 kg n ha-1) in rice and (20 kgn ha-1 ) in mungbean for all the years. system productivity in n unfertilized plots increased when straw was retained. the results suggest that n fertilizer rates can be reduced when straw is retained. soil organic matter in surface soil layers of the prb had increased by 0.72% after eight years (8 ricewheat-mungbean crop cycles) with 30% sr. it may be inferred that straw retention is an important component of soil management and may have long term positive impacts on soil quality compared with conventional tillage with 0 % sr. the combination of prb with nutrients and residues retained appeared to be a very promising technology for sustainable intensification of rw systems in the drought prone area of bangladesh. introduction land degradation and soil fertility declining are among the main causes of the stagnation and fall of agricultural productivity in many tropical countries including those with intensive irrigated cropping systems. approximately 85% of the area planted with intensive rice-wheat (rw) sequential cropping is found in the indo-gangetic plain (igp) of south asia in india, pakistan, nepal and bangladesh (timsina and connor, 2001). rice is transplanted in flat fields are typically ponded for long periods or continuously from transplanting until shortly before harvest. this negatively affects soil properties for the following non-puddle crop (hobbs ad giri, 1998). wheat is then planted in these structurally disturbed soils, often after many tillage operations to get the prepared the seedbed or increasingly, with little soil disturbance using zero-till seed drills. a change from growing crops on the flat to raised beds offers more effective control of irrigation water and drainage. this may be particularly beneficial for non-rice crops grown in rotation with rice, allowing better rainwater management during the monsoon season for rice. connor et al. (2003) suggested that permanent raised beds might offer the farmers further significant advantages related to increased opportunities for crop diversification, mechanical weeding and placement of fertilizers, relay cropping and inter-cropping, and reduced tillage and water saving. there are also indications that crop yields from beds can be further increased by using higher rates of n fertilizer and later irrigation because of the reduced risk of lodging (sayre and ramos, 1997). raised beds are increasingly used in many developed and developing countries in mechanized agriculture but have been 24 hossain et al. introduced only recently in bangladesh, with the aim of improving system productivity (talukder et al., 2002). inclusion of grain legumes in the dry-wet transition of rice-wheat cropping system as a third crop may be the other option of increasing cropping intensity, soil fertility and productivity of the system. although the non rice season across the rice-wheat area is characterized with low rainfall, heavy pre-monsoonal rain can have disastrous effects on the third crop, such as maize or mungbean grown after wheat or before rice, both during establishment and grain filling causing water logging (timsina and connor, 2001; quayyum et al., 2002). due to lack of crop establishment technique and temporary water logging at reproductive stage, inclusion of a grain legume like mungbean in rice-wheat cropping system very often faces problem. bed planting may be a solution of this problem because raised beds not only facilitates irrigation but also drainage and therein lays their potential to increase the productivity of crops other than rice in the system. growing leguminous crops in a cropping system is beneficial not only for economic products but also for soil amelioration (singh et al., 1993). the common practice of rice in puddle soils destroys the soil physical structure that has implications for the following wheat crop (hobbs et al., 2000). crop residues are an important source of soil organic matter vital for the sustainability of agricultural ecosystems. about 25% of n and p, 50% of s and 75% of k uptake by cereal crops is retained in crop residues, making them valuable nutrient sources (singh, 2003). however, straw retention is not a common practice in the rw systems of bangladesh. wheat and rice straw are usually removed from fields for use as cattle feed and thatching material for houses or for fuel, leaving little for incorporation into the soil. as a result, soil organic matter levels have declined in these cropping systems, and optimization of nutrient uptake and absorption efficiency. in a study talukder et al. (2002) found that n use efficiency was the highest in permanent raised beds, giving higher yields than a conventional system. limon-ortega et al. (2000) observed that permanent beds with straw retention had the highest mean wheat grain yields (5.57 t ha-1), n use efficiency (28.2 kg grain kg-1 of n supply) and total n uptake (133 kg ha-1), with positive implications for soil health. thus, management of crop residues and beds, along with efficient n fertilization strategies are new farming practices that can increase and maintain yields from the intensive rw system in bangladesh. therefore, this study was undertaken in a drought prone area in north-western part at rajshahi to evaluate the system productivity, soil fertility and n use efficiency of intensive wheat-mungbean-rice crops sequence tested on permanent raised bed (prb) compared to conventionally tilled systems. materials and methods wheat (triticum aestivum)mungbean (vigna radiata)monsoon rice (oryza sativa) cropping pattern was followed for 8 times, at the regional wheat research centre, shyampur, rajshahi, bangladesh (24o3'n, 88041e, 18 m above sea level). the site has a subtropical climate and is located in agro ecological zone 1 (old himalayan piedmont plains) on flood-free high land, with course-textured, highly permeable soil (barc, 1997). the area receives 1,757 mm mean annual rainfall, about 97% of which occurs from may to september. total rainfall was the highest during the mungbean season and the lowest in the wheat season in all years (table 1). the trial involved a three-crop sequence i.e., rice-wheat-mungbean (rwm) planted on raised beds and conventional. rice was transplanted (one 25-day-old seedlings per hill) with spacing 30 cm x 15 cm in late july and harvested in late november by hand. wheat was seeded with 100 and 120 kg seed ha-1 for beds and conventional, respectively, in late november and harvested in late march. after harvest of wheat, mungbean were planted in march with seeding rate of 35 kg ha-1 in early april and harvested in mid july for both beds and conventional. the trial was originally established as a prb experiment with two straw management practices (main plots-30% straw retention (sr) and 0% sr) and five n levels (subplots 0, 40, 80, 100 and 120% of recommended). the area of each subplot was 15 m2 (5m x 3m). the 25 bed planting effect of rice and wheat in drought prone area experiment consisted of 20 subplots with four tillage/straw treatments (30% sr + prb, 30% sr + ctp, 0% sr + prb and 0% sr + ctp) and five n levels (0, 40, 80, 100 and 120% of recommended) with three replication. after planting the wheat or rice, straw from the preceding cereal crops was returned as a mulch into the plot from which it had been removed at harvest. after harvesting and threshing, the rice and wheat straw were returned without chopping as standing way. the width of the beds was 60 cm (furrow to furrow) and the depth of the furrows on average was 15 cm. two rows of wheat (var. shatabdi) or rice (var. brri dhan 49) with a spacing of 30 cm, were planted by hand sowing on the beds, two rows of rice on the beds, mungbean (var. bari mungbean-6) was sown by bed former in the furrows between the beds. the mungbean was harvested about 60 days after sowing (das). in ctp, wheat, rice and mungbean were planted in 20 cm, 30 x 15 cm and 30 cm in continuous rows. a basal dose of p (20, 22 and 26 kg ha-1) from triple super phosphate, k (15, 35 and 33 kg ha-1) from muriate of potash and s (10, 11 and 20 kg ha-1) from gypsum was applied to mungbean, rice and wheat, respectively. in rice the entire amount of pks was broadcasted before transplanting and mulching on both prb and ctp. for ctp the fertilizer was broadcast before tillage as is the usual practice. the recommended rate of n (80 kg ha-1for rice, 100 kg ha-1 for wheat and 20 kg ha-1 for mungbean) was applied as urea. for mungbean all n was applied before seeding. with ctp, n was broadcast, while with beds it was banded on top of the soil between two rows in three equal installments 15, 30 and 45 days after transplanting, while wheat, two-thirds of the n was applied before seeding and the remaining onethird at crown root initiation (cri). sufficient irrigation water was applied to fill the furrows between the raised beds. total system productivity total system productivity (tsp) was calculated using the method of tanaka (1983). based on the composition of harvested organs for mungbean and their conversion efficiencies, the equivalent yields for various crops can be calculated (tanaka, 1983). total system productivity (tsp) for each treatment was calculated as the total annual productivity (or the annual total of economic yield of the individual crops) based on equivalent yields. estimation of nitrogen uptake the result was expressed in percentage. n-uptake by grain and straw also were calculated by the following formulae: n-uptake by grain (kg ha-1) = total n (%) in grain x grain yield (kg ha-1) 100 n-uptake by straw (kg ha-1) = total n (%) in straw x straw yield (kg ha-1) 100 different measures of nitrogen use efficiency the different measures of n-use efficiencies; physiological efficiency (pe), fertilizer recovery efficiency (re), and agronomic efficiency (ae) were calculated as described by dobermann and fairhurst (2000). total n uptake as used in this term referred to n uptake by above ground biomass (grain and straw) only recovery efficiency (re) of added n was calculated as: re (%) = total n uptake (kg n ha -1) of the treatment total n uptake (kg n ha-1) of the control x 100 [1] applied n (kg n ha-1) of the treatment physiological efficiency (pe) of added n was calculated as: pe(kg grain kg -1 n uptake) = grain yield (kg ha-1) of the treatment – grain yield (kg ha-1) of the control [2] total n uptake (kg n ha-1) of the treatment – total n uptake (kg n ha-1) of the control 26 hossain et al. agronomic efficiency (ae) of added n was calculated as: ae(kg grain kg -1 n applied)= grain yield (kg ha -1) of the treatment – grain yield (kg ha -1) of the control [3] applied n (kg n ha -1) of the treatment statistical analysis of data the data were analyzed statistically following computer package mstat and the significance of mean differences was adjusted by duncan’s multiple range test. results and discussion total system productivity (tsp) tsp increased by 12-15% with 30% straw retention with prb (12 t ha-1yr-1) compared with ctp with 0% straw retention (fig. 1). for all crops the highest system yields obtained in prb + 30% sr. yields on prb consistently increased significantly as sr increased from 0% to 30. the lower system productivity with 0% sr with ctp was associated with reduced crop growth. similar observations were made by singh et al. (2003) in mexico. fig. 2 presents the system yields of different tillage options and n levels (means of three years), illustrating that tsp increased significantly by 11 % in rice and 14 % in mungbean with increasing n levels up to 100 %; and by 16 % in wheat up to 120 % n. for all crops the highest system productivity occurred in prb with 120 % n (120 kg n ha-1 in wheat) and 80 % n both in rice and mungbean (80 kg n ha-1 in rice, 20 kg n ha-1 in mungbean). yields tended to be lower with lower nitrogen levels for all crops. similar observations were made by yadvinder et al. (2006) in india. averaged over the years, prb + 30 % sr with 100 % n gave a 17 % increase in wheat yield over prb + 0 % sr at the same n rate, but there was no significant mungbean yield increase with additional n with 30% sr. however, yield of prb + 30% sr with 120% n was significantly higher than prb + 0 % sr with 100% n in wheat. average rice yield on prb + 30% sr with 50% n was significantly higher than with 0 % sr at the same n rate, and there was no further yield increase at higher n rates. rice yield declined with 30 % sr at the two highest n rates, mostly due to lodging. 0 2 4 6 8 10 12 14 bed x 0% straw conv x 0% straw bed x 30% straw conv x30% straw tillage options x straw levels to ta l s ys te m s pr od uc tiv ity (t /h a) rice wheat mungbean 0 2 4 6 8 10 12 14 be dx 0% n co nv x0 %n be dx 40 %n co nv x4 0% n be dx 80 %n co nv x8 0% n be dx 10 0% n co nv x1 00 %n be dx 12 0% n be dx 12 0% n tillage optionsx n levels to ta l s ys te m p ro du ct iv ity (t /h a) rice wheat mungbean fig 1. total system productivity under tillage options and straw levels in rice-wheatmungbean system fig. 2. total system productivity under tillage options nitrogen levels in rice-wheatmungbean systems lower system productivity also occurred from 0% n with ct due to less n uptake and use efficiency. yields tended to be lower in differences of nitrogen levels for all crops. similar observations were made 27 bed planting effect of rice and wheat in drought prone area by yadvinder et al. (2006) in india. yields tended to be lower in differences at four n levels in wheat, at three n levels in rice and at two lowest n levels in mungbean (fig. 2). averaged over the 7 years, prb + 30% sr with 100 % n gave 17 % increased in wheat yield over prb + 0 % sr at the same n rate (fig. 2). however, yield of prb + 30% sr with 120% n was significantly higher than prb + 0% sr with 100% n. average rice yield on prb + 30% sr with 50% n was significantly higher than with 0% sr at the same n rate, and there was no further yield increase at higher n rates, rice yield declined with 30% sr at the two highest n rates, mostly due to lodging. maximum average wheat grain yield was obtained on prb from 120 % n with 30 % sr and after 7 years yield was similar when 80 % n with 30% straw retention (fig. 2). these yield increases with straw retention are probably due to suppression of soil evaporation, less weeds and more efficient use of fertilizers. limon-ortega et al. (2000) reported that permanent beds both wheat and maize yields when grown with higher rates of n fertilizer. rice yield was comparatively low under the ctp system due to water logging and the resultant acute weed stress (poor crop growth could not compete as well with weeds) in early as well as late growth stages. variability in wheat yields in bangladesh is mostly the result of the high temperature that can occur during the grain filling phase, especially for late-sown crops (midmore et al., 1984). nitrogen uptake and use efficiency 0 20 40 60 80 100 120 140 160 0 40 80 100 120 applied n levels (% recom m ondation) n up ta ke (k g/ ha ) bed + 0%sr conv + 0%sr bed + 30%sr conv + 30%sr fig. 3. total nitrogen uptake under tillage options, straw and nitrogen levels in ricewheat-mungbean systems total n uptake increased with increasing up to 120 % and it was similar as 80 % in all crops. the increased n uptake was 31% in rice, 25 % in wheat and 19 % in mungbean over conventional (fig. 3). retention of straw resulted in increased n uptake in both n fertilized and zero n plots. nitrogen uptake was significantly (p<0.5) influenced by straw retention and n level. in prb + 30% sr plots, total n uptake by rice was maximum at 50-100 % by rice, 80-120 % by wheat and 50-100 % by mungbean. in contrast, in both prb and ctp without straw retention, there was a consistent trend for increasing n uptake up to 120 % n rate in all crops. limon-ortega et al. (2000) also observed that permanent beds with straw retention gave the highest wheat grain yields (5057 t ha-1), n use efficiency (28.2 kg grain kg-1 of n supply) and total n uptake (133 kg ha-1). yield in n unfertilized rice, wheat and mungbean increased when straw was retained and this appeared to be due to an increased uptake of n. fertilizer use efficiency may be increased by implementing permanent bed management in addition to reducing weed and crop lodging problems. n use efficiency (calculated pe, ae and re) decreased as n rate increased in all treatments (table 1). at the lowest n rate there was a consistent trend for higher ae on prb with 30 % sr and 0 % sr. there was a consistent trend for higher pe on prb as the amount of sr increased from 0 to 100% across all crops. similar observations were made by yadvinder et al. (2004). they reported that ae was significantly higher in straw retained + green manure cultivated treatments than other treatments for wheat. n uptake helps the decomposition of retained straw, resulting in a higher uptake of nutrients and more efficient use of water. n use efficiencies increases rice life 3-5 days. table 1. nitrogen use efficiency of rice, wheat and mungbean (2004-12) as influenced by straw retention, 28 hossain et al. tillage and n level at rajshahi, bangladesh. treatments ae (kg grain kg-1n applied) pe (kg grain kg-1n uptake) re (%) rice wheat mungbean rice wheat mungbean rice wheat mungbean 30 % sr + prb n 0 64.5 44.5 49.5 n 50 49.3 33.5 16.5 53.4 33.5 36.8 95.4 96.8 112.7 n 100 41.2 24.3 10.6 45.8 26.2 32.3 89.8 81.7 106.3 n 150 23.5 18.5 6.7 41.4 25.7 25.3 66.2 64.7 95.7 n 200 20.2 14.5 3.9 38.2 23.4 22.4 50.9 45.2 77.6 0 % sr + prb n 0 58.3 39.5 43.5 n 50 42.3 28.3 12.8 49.8 29.5 31.5 87.8 84.5 95.3 n 100 34.5 21.5 9.7 41.5 22.4 27.3 78.6 74.6 87.3 n 150 21.3 14.3 6.3 38.9 18.5 22.5 58.6 62.5 82.1 n 200 18.5 10.5 3.2 29.6 11.5 18.3 42.5 53.2 63.2 30 % sr + ctp n 0 59.6 44.5 44.5 n 50 45.3 29.5 14.5 50.2 34.2 32.4 90.2 87.3 98.6 n 100 38.5 22.3 10.2 43.2 25.3 28.3 82.3 77.3 89.3 n 150 25.4 19.3 6.4 37.8 22.3 23.2 60.5 65.3 82.5 n 200 20.3 12.4 3.4 30.5 13.5 19.7 44.5 53.4 68.5 0 % sr + ctp n 0 52.3 45.3 57.6 n 50 38.7 24.1 12.6 49.6 33.7 43.5 82.7 81.3 97.2 n 100 33.4 20.4 9.6 42.2 27.9 34.5 71.4 71.2 81.4 n 150 19.2 16.2 6.4 37.5 26.8 30.9 48.9 59.6 71.6 n 200 14.7 9.9 2.6 33.2 24.8 24.3 39.2 44.3 58.5 prb = permanent raised beds, sr = straw retention; ctp = conventional tillage practice soil organic matter (som) after 8 years (2004-12), retention of straw from all three crops in the zero-till prb system had increased the soil organic matter by 0.72% (table 2). while some of the increase may have been due to formation of the beds from topsoil, the change in organic c increased as the rate of residue retention increased from 100%, indicating that straw retention also affected organic c on the beds. 30% sr with prb, p, k and zn availability increased. at low n levels (0 and 50% of recommended) there appeared to be a slight decline in soil organic c. after 8 years of ctp without residues, soil organic c had decreased by a few percent at all n rates and there was a consistent trend for a large decline at lower n rate. the increase in soil organic c with 30% sr at 50-150% n was almost double that with 0 % n. kumar and goh (2000) reported that, in the longer term, residues and untilled roots from crops can contribute to the formation of som. after the seven rwm crop cycles, the soil color had darkened, presumably due to the build-up of organic matter in the topsoil (fig. 4). table 2. chemical properties changes in soil for 30% straw from 2004-2012 bed x 0 % straw bed x 0 % straw conv. x 0% straw bed x 30% straw conv. x 30% straw ph 8.2 8.3 7.7 7.9 om (%) 1.06 1.06 1.78 1.24 total n (%) 0.11 0.12 0.09 0.11 p (mg g-1 soil) 15.12 14.5 19.87 16.75 k ml (eq 100 g-1 soil) 0.37 0.39 0.48 0.43 29 bed planting effect of rice and wheat in drought prone area s (mg g-1 soil) 17.25 24.2 15.85 21.27 zn (mg g-1 soil) 0.23 0.12 0.37 0.17 b (mg g-1 soil) 0.31 0.21 0.35 0.24 ec (ds m-1) 0.97 1.24 0.92 1.17 table 3. soil chemical properties changes for 30 % straw retention after eight years characteristics initial final difference ph (1:2.5 in water) 8.3 8.0 0.3 organic matter (%) 1.10 1.82 + 0.72 total n (%) 0.12 0.09 0.03 exch. k (ml eq 100g-1 soil) 0.26 0.48 + 0.22 avail. p (mg g-1 soil) 24.5 52.5 + 38.0 avail. s (mg g-1 soil) 25.6 38.9 + 13.3 avail. zn (mg g-1 soil) 0.84 6.13 + 5.29 avail. b (mg g-1 soil) 0.19 0.37 + 0.18 ca (ml eq 100g-1 soil) 18.22 21.24 + 3.02 mg (ml eq 100g-1 soil) 5.05 6.17 + 1.12 fe (mg g-1 soil) 76.4 63.5 12.9 mn (mg g-1 soil) 22.9 12.7 10.2 economic evaluation of conservation agriculture (ca) for economic evaluation, considered 20 farmers for permanent bed and 25 farmers for new bed in both the cases. from table 4, observed that total 25% cost saved of t. aman rice production in prb and 17% cost saved in new bed over farmers practice as well as more than double net return from both permanent and new bed system over farmers practice (fp). it also observed that economically higher return from both prb (28%) and new beds (34%) than fp. however, ca is more economically viable than fp. table 4. economic performance of ca for t aman rice in 2010-12 from farmers factors permanent (n=20) new (n=25) bed fp change bed fp change tillage / land preparation 250 480 -47% 480 480 seed 140 200 -30% 140 200 -30% fertilizer & pest management 650 780 -16% 650 780 -16% irrigation 450 760 -40% 480 760 -36% weeding 395 550 26% 420 550 -23% harvest 510 560 -9% 520 560 -7% threshing 230 200 230 200 total costs 2625 3530 -25% 2920 3530 -17% yield (kg bigha-1) 760 590 28% 795 590 34% value @ tk 10 kg-1 7600 5900 28% 7950 5900 34% net return 4975 2370 2605 (2.1x) 5030 2370 2660 (2.12x) conclusion retention of 30% crop residues together with zero-till permanent bed system offers an important soil restorative management strategy likely to have a long-term positive impact on soil quality and crop productivity in intensive rice-wheat-mungbean (rwm) cropping systems in bangladesh. besides, residual straw and roots added more organic matter and nutrients into the soils under prb, resulting in increased nutrient uptake by the crops. crop productivity on beds with 30 % straw retention increased by 30 hossain et al. 11% for rice, 17% for wheat and 21% for mungbean at 100% n rates over a 7 year cycle of the rwm cropping pattern compared with 0 % sr+ prb at the same n rate. yield in n unfertilized rice, wheat and mungbean increased when straw was retained and this appeared to be due to an increased uptake of n. retention of crop residues as a mulch reduced moisture depletion and increased som content over relatively short periods of time. fertilizer use efficiency may be increased by implementing permanent bed management in addition to reducing weed and crop lodging problems. permanent raised beds would also help ameliorate the adverse effects of tillage on soil structure, which might lead to water logging under excess water conditions and hamper establishment, growth and development of most crops including mungbean. the use of prb reduces the overall cost of production and long turnaround time. thus, results showed that prb with straw retention could help to intensify rw systems to rwm systems under high degrees of management as such further on-farm adaptive trial with farmers is needed to verify the technology. acknowledgement we acknowledge the international wheat and maize improvement centre (cimmyt) for financial support for conducting this study. references gomez, k. a. and a. a. gomez. 1984. statistical procedures for agricultural research (second edition).john wiley & sons, inc., irri, philippines, 680p. govaerts b, k. d. sayre and j. deckers. 2006. towards minimum data sets for soil quality assessment. the case of zero-tillage wheat/maize rotations in the highland of mexico. soil till. res. 87: 163-174. gupta, r. k., r. k. naresh, p. r. hobbs and j. k. ladha. 2002. adopting conservation agriculture in ricewheat systems of the indo-gangetic plainsnew opportunities for saving on water. paper presented at the "water wise rice production workshop", 5-10 april 2002, irri, philippines. hobbs, p. r and r. k gupta. 2000. ‘soil and crop management practices for enhanced productivity of the ricewheat cropping system in the sichuan province of china’. rice-wheat consortium paper series 9. (rwc, new delhi, india). ippc. 2007. fourth assessment report of the intergovernmental panel on climate change: the impacts, adaptation and vulnerability. cambridge university press, united kingdom and new york, ny, usa. kataki, p. k. 2001. the rice-wheat cropping system in south: trends, constraints and productivitya prologue, j. crop prod. 3: 1-26. kumar, k. and k. m. goh. 2000. crop residue management, effects on soil quality, soil nitrogen dynamics, crop yield and nitrogen recovery. adv. agron. 68: 197-319. lauren, j. g., j. m. duxbury, m. i. hossain, g. sah, a. s. m. h. m. talukder and c. a. meisner. 2006. permanent raised bed cultivation improves nitrogen and water use in rice-wheat cropping systems of south asia. 18th world science congress, usa. limon-ortega, a. l., k. d. sayre and c. a. francis. 2000a. wheat nitrogen use efficiency in a bed planting system in northwest mexico. agron. j. 92: 303-308. limon-ortega, a., k. d. sayre and c. a. francis. 2000b. wheat and maize yields in response to straw management and nitrogen under a bed planting system. agron. j. 92: 295-302. quayyum, m. a., j. timsina, m. a. h. s. jahan, r. a. begum and d. j. connor. 2002. grain yield and system productivity for wheat-mungbean-rice and wheat-maize rice sequences in northern bangladesh. thai j. agric. sci. 35: 51-62. 31 bed planting effect of rice and wheat in drought prone area rwc-cimmyt. 2003. addressing resource conservation issues in rice-wheat systems of south asia: a resource book. (rwc-cimmyt, new delhi, india). sayre, k. d., a. limon, and b. govaerts. 2005. experiences with permanent bed planting systems. in: roth, c. h., fischer, r. a., meisner, c. a. (eds.). evaluation and performance of permanent raised bed cropping systems in asia, australia and mexico, proceedings of a workshop, griffith, australia, 1-3 march 2005. aciar proceedings no. 121, pp.12-25. singh, y. 2003. crop residue management in rice-wheat system. 2003. in: addressing resource conservation issues in rice-wheat consortium for the indo-gangetic plains. cimmyt, new delhi, india, p.153. singh, h., and k. p. singh. 1995. effect of plant residue and fertilizer on grain yield of dryland rice under reduced tillage cultivation. soil till. res. 34: 115–125. tanaka, a. 1983. physiological aspects of productivity in field crops. in: potential productivity of field crops under different environments. irri, los banos, philippines, pp.61-80. talukder, a. s. m. h. m., c. a. meisner, m. j. kabir, a. b. s. hossain and m. harun-ur-rashid. 2004. productivity of multi-crops sown on permanent raised beds in the tropics. in: new direction for a diverse planet: handbook and abstracts for the 4th international crop science congress, brisbane, australia, 26 september 01 october 2004, p.173. talukder, a. s. m. h. m., m. a. sufian and c. a. meisner. 2002. rice, wheat and mungbean yields in response to n levels and management under a bed planting system. in: proceedings published in the 17th world congress of soil science, bangkok, thailand, v. 1, symposium no. 11, p.351. timsina, j. and d. j. connor. 2001. productivity and management of rice–wheat cropping systems: issues and challenges. field crops res. 69: 93-132. witt, c., k. g. cassman, d, c. olk, u. biker, s. p. liboon, m. i. samson and j. c. g. ottow. 2000. crop rotation and residue management effects on carbon sequestration, nitrogen cycling and productivity of irrigated rice systems. plant soil. 225: 263-278. yadvinder, s., s. bijay, and j. timsina. 2005. crop residue management for nutrient cycling and improving soil productivity in rice-based cropping systems in the tropics. adv. agron. 85: 269-407. yadvinder, s., s. bijay, j. k. ladha, c. s. khind and t. s. kera. 2006. effects of residue decomposition on productivity and soil fertility in rice-wheat rotation. soil sci. soc. amer. j. 68: 851-864. m. ilias hossain1, m. i. hossain2, m. r. i mondal3, m. k. sultan4, m. gathala5 and t. p tiwary5 key words: bed planting, cropping system, productivity, sustainable, drought bangladesh agron. j. 2019, 22(2): 11-24 physiological basis of salinity tolerance in foxtail millet s. akter​1*​, m.a. mannan​1​, m.a.a. mamun​1​ and m.s. islam​2 1​department of agronomy,​ 2​department of soil science bangabandhu sheikh mujibur rahman agricultural university, gazipur-1706, bangladesh *corresponding e-mail: mannanbsmrau@yahoo.com (received: ​17 december 2019,​ accepted: ​04 january 2020​) keywords:​ physiology, salinity, tolerance, foxtail millet abstract a pot experiment was conducted to study the effects of salt stress on physiological parameters associated to salinity tolerance in foxtail millet plant in the department of agronomy, bangabandhu sheikh mujibur rahman agricultural university, gazipur, bangladesh during march to may, 2018. four foxtail millet genotypes namely i) bd-881 ii) bd-897 iii) bd-878 and iv) bari kaon-1 were grown and each pot was irrigated using three levels of saline water viz. control (tap water), 60 mm saline water and 120 mm saline water. results indicated that genotypic variability was profound in salinity tolerance in foxtail millet. the leaves of bd-878 maintained higher water content, higher accumulation of proline, and lower accumulation of malondialdehyde (mda) as well as less reduction of chlorophyll compared to other genotypes studied. bd-878 also showed relatively higher salinity stress tolerance, while bd-897 was susceptible in relation to yield. higher salinity tolerance in bd-878 was associated with higher relative leaf water and chlorophylls with accumulation of higher amount of proline and lower accumulation of malondialdehyde content. introduction the changes foreseen under climate change scenarios are the changes in the pattern of rainfall, rather than the quantum, leading to long spells of drought and spells of water-logging of the soils as well as salinity. foxtail millet is considered to be an ideal crop for the changing climate due to its short duration, high photosynthetic efficiency, nutritional richness and low incidence of pest and diseases (vetriventhan ​et al​., 2012) and has been reported to have comparable tolerant level to drought (doust ​et al​., 2009) and salinity (kafi ​et al​., 2009). foxtail millet can be a potential crop for salt affected soils due to its high level of tolerance to salinity (maas, 1985) and the salt ‘escape’ potential due to its short growing duration. salt stress induces several morphological, physiological, biochemical and molecular responses in several crop plants, which would help them to adapt to such limiting environmental conditions (arora ​et al., ​2002). it inhibits the photosynthesis of plants, causes changes of chlorophyll contents and damages the photosynthetic apparatus (escuredo ​et al., 1998). osmotic adjustment is the decrease of osmotic potential by the active accumulation of organic as well as inorganic solutes within the cells. high concentrations of inorganic ions become detrimental to cellular metabolism and must be sequestered in the vacuole. in order to keep osmotic balance, specific types of organic molecules (such as soluble sugars, betains, proline etc) are accumulated in the cytoplasm. those compounds protect plants 12 akter et al. against stresses by cellular adjustment through the protection of membranes integrity and enzymes stability (farooq ​et al., ​2009). these compounds are termed as compatible solutes, because they can be accumulated in high concentrations without impairing normal physiological function. so, aiming of this research work was to analyze the changes of morpho-physiological parameters that are associated with the salinity tolerance in foxtail millet as well as to study the effects of salinity on dry matter accumulation and yield of foxtail millet. materials and methods the experiment was conducted at the department of agronomy, bangabandhu sheikh mujibur rahman agricultural university, gazipur, bangladesh. the experimental site is the center of madhupur tract (aez 28) (24.09​ο n latitude and 90.26​ο e longitudes) at 8.4 m above the mean sea level. the experiment was carried out employing 4 foxtail millet genotypes namely i) bd-881 ii) bd-897 iii) bd-878 and iv) bari kaon-1. the plants were grown in plastic pots of 24 cm diameter × 30 cm height in size filled with soil inside plastichouse under natural light during march to may, 2018. the soil used in the pot was clay loam in texture and poor fertility status. the ph of the soil was 7.1, organic carbon0.60%, total n0.05%, available p 0.08 mg/100 g dry soil, exchangeable k0.33 cmol​c ​kg​-1 ​dry soil and cec14.58 cmol​c ​kg​-1 ​dry soil. compost (​1​/4 th of the soil volume) and 0.27-0.28-0.20 g of urea, triple super phosphate and muriate of potash per pot for supplying n, p​2​o​5 and k​2​o, respectively were incorporated uniformly into the soil. the compost was made mostly from cow dung which contained 0.8% n, 0.6% p​2​o​5 ​and 1.0% k​2​o on dry weight basis. ten to fifteen bold seeds were sown in each plastic pot containing about 12 kg air dried soil. after seedling establishment, six uniform and healthy plants were allowed to grow in each pot. three levels of salt solution viz. i) tap water (control) ii) 60 mm salinity and 120 mm salinity were applied from 14 days after sowing to maturity. normal management practices were applied for all the treatments. the experiment was conducted with completely randomized design (crd) with three replications. the plant height and total dry weight (stem +leaf) were measured at 20 and 40 days after salt imposition (dasi). leaf water content, proline, melondialdehyde (mda) content and chlorophyll content were measured at flowering stage. the leaf water content (rwc) was measured using the formula: [(fw ​˗ dw)/(tw ​˗ dw)] × 100 where, tw = turgid weight of the leaf, fw = fresh weight of the leaf, dw = dry weight of the leaf. proline, melondialdehyde (mda) content and chlorophyll content was measured according to bates ​et al​. (1973), health & packer (1968) and witham ​et al. (1986), respectively. at maturity two plants were collected from each pot, and tiller number / plant, panicle number / plant, panicle weight / plant and seed yield / plant were recorded. data of salinity stress (60 mm and 120 mm) were compared with those in control (non saline water) treatment in order to understand the relative growth reduction of the individual plant part. the recorded data on various parameters were statistically analyzed by “cropstat”. the treatment means were compared by least significance difference (lsd) test at 5% level of significance (gomez & gomez, 1984). results and discussion plant height the effect of salt stress on plant height was statistically significant at 20 and 40 days after salt imposition (table 1). at 20 days, the plant height under control condition was the highest in bd-897, while the lowest was in bari kaon-1. at 60 mm saline condition the highest plant height was recorded in bd-897 and the lowest was in bari-kaon-1. relative (per cent of physiological basis of salinity tolerance in foxtail millet 13 control) plant height of the genotypes ranged from 91.87% to 96.44%. highest relative plant height was obtained from genotype bari kaon-1 (96.44%), followed by bd-878 (96.04%), and bd-897 (91.94%) and it was lowest in bd-881 (91.87%). at 120 mm saline condition the highest plant height was recorded with bd-897 and the lowest was in bari-kaon-1. relative (per cent of control) plant height of the genotypes ranged from 84.88% to 87.09%. highest relative plant height was obtained from genotype bd-878 (87.09%), followed by bari-kaon-1 (86.67%) and bd-881 (84.98%) and it was lowest in bd-897 (84.88%). plant height reduction due to salinity was lower in bd-878 (12.91%) while that was higher in bd897 (15.12%). after 40 days, the highest plant height was recorded in bd-897 and the lowest was demonstrated from bari kaon-1 under control condition. at 60 mm saline condition the highest plant height was recorded with bd-878 and the lowest was in bari kaon-1. relative (per cent of control) plant height of the genotypes ranged from 85.41% to 91.10%. highest relative plant height was obtained from genotype bd-878 (91.10%), followed by bd-897 (86.90%) and bd-881 (86.71%) and it was lowest in bari kaon-1 (85.51%). at 120 mm saline condition the highest plant height was recorded with bd-878 and the lowest was in bari kaon-1. relative (per cent of control) plant height of the genotypes ranged from 70.12% to 75.95%. highest relative plant height was obtained from genotype bd-878 (75.95%), followed by bd-881 (73.08%) and bari-kaon-1 (72.22%) and it was lowest in bd-897 (70.12%). plant height reduction due to salinity was lower in bd878 (24.05%), while that was higher in bd-897 (29.88%). therefore, bd-878 showed relatively higher salinity tolerance in relation to plant height than other genotypes studied. the lower height in the plants under salinity occurred, probably due the aba action, in which it is produced in the cells under water stress condition and this way inhibit the cell division and / or dna synthesis. similar results on the height reduction in plant under stress were described by lacerda ​et al. ​(2003) working with genotypes of ​sorghum bicolor​ under salt stress. table 1. plant height (cm) of foxtail millet genotypes as affected by salinity at different days after salt imposition (dasi) genotype s 20 dasi 40 dasi control 60 mm salinity 120 mm salinity control 60 mm salinity 120 mm salinity bd881 135.33​±​78.13* 124.32​±​71.78 (91.87) 115.00​±​66.40 (84.98) 195.6​±​8.19 169.67​±​4.67 (86.71) 143​±​4.93 (73.08) bd897 136.67​±​78.90 125.65​±​72.55 (91.94) 116.00​±​66.97 (84.88) 208.67​±​2.72 181.33​±​3.52 (86.90) 146.33​±​2.8 (70.12) bd878 126.33​±​72.94 121.30​±​70.05 (96.04) 105.67​±​61.01 (87.09) 202.33​±​2.84 184.33​±​4.48 (91.10) 153.67​±​2.72 (75.95) bari kaon-1 75.00​±​43.30 72.33​±​41.76 (96.44) 65​±​37.53 (86.67) 96​±​2.08 82​±​2.89 (85.41) 69.33​±​3.18 (72.22) lsd​(0.05) 1.10 2.05 cv (%) 22.86 31.12 * indicate se value, values in parenthesis indicate per cent of control. studies carried out by wang (2005) revealed that the aba induce the gene expression that codify the inhibited protein of the cyclin-dependent activity (ickl), coinciding with the results found by jakoby ​et al. (2006) on extreme important of this metabolic in cell division process and consequently development and growth of plant. total dry matter weight 14 akter et al. the effect of salt stress on total dry weight (leaf + stem) was statistically significant at 20 and 40 days after salt imposition (table 2). at 20 days, the total dry weight under control condition was the highest in bd-878, while the lowest was in bari kaon-1. at 60 mm saline condition the highest total dry weight was recorded with bd-878 and the lowest was in bari-kaon-1. relative (per cent of control) total dry weight of the genotypes ranged from 70.73% to 82.88%. highest relative total dry weight was obtained from genotype bd-878 (82.88%), followed by bd-881 (79.70%), and bd-897 (73.66%) and it was lowest in bari kaon-1 (70.73%). at 120 mm saline condition the highest total dry weight was recorded with bd-897 and the lowest was in bari kaon-1. relative (per cent of control) total dry weight of the genotypes ranged from 53.60% to 73.90%. highest relative total dry weight was obtained from genotype bd-878 (73.90%), followed by bari-kaon-1 65.70%) and bd-897 (65.34%) and it was lowest in bd-881 (53.60%). total dry weight reduction due to salinity was lower in bd-878 (73.90%) while that was higher in bd-(881 53.60%). after 40 days, the highest total dry weight was recorded in bd-881 and the lowest was demonstrated from bari kaon-1 under control condition. at 60 mm saline condition the highest total dry weight was recorded with bd-878 and the lowest was in bari kaon-1. relative (per cent of control) total dry weight of the genotypes ranged from (70.44% to 86.92%). highest relative total dry weight was obtained from genotype bd-878 (86.92%), followed by bd-881 (78.16%) and bd-897 (72.72%) and it was lowest in bari kaon-1 (70.44%). table 2. total dry weight (g) of foxtail millet genotypes as affected by salinity at different days after salt imposition (dasi) genotypes 20 dasi 40 dasi control 60 mm salinity 120 mm salinity control 60 mm salinity 120 mm salinity bd881 11.43​±​6.60* 9.11​ ±​5.26 (79.70) 6.13​±​3.54 (​53.60​) 47.01​±​8.71 36.74​±​3.60 (78.16) 29.89​±​2.58 (63.58) bd897 11.59​±​6.69 8.54​±​4.93 (73.66) 7.57​±​4.37 (​65.34​) 45.31​±​3.15 32.97​±​4.12 (72.72) 24.5​±​2.30 (54.06) bd878 12.19​±​7.04 10.10​±​5.83 (82.88) 7.47​±​4.31 (​73.90​) 45.21​±​8.08 39.30​±​1.87 (86.92) 34.93​±​1.51 (77.26) bari kaon-1 8.75​±​5.05 6.19​±​3.57 (70.73) 5.75​±​3.32 (​65.70​) 27.17​±​0.95 19.14​±​1.50 (70.44) 15.78​±​1.60 (58.06) lsd​(0.05) 0.15 0.10 cv (%) 25.50 30.94 * indicate se value, values in parenthesis indicate per cent of control. at 120 mm saline condition the highest total dry weight was recorded with bd-878 and the lowest was in bari-kaon-1. relative (per cent of control) total dry weight of the genotypes ranged from 54.06% to 77.26%. highest relative total dry weight was obtained from genotype bd-878 (77.26%), followed by bd-881 (63.58%) and bari-kaon-1 (58.06%) and it was lowest in bd-897 (54.06%). total dry weight reduction due to salinity was lower in bd-897 (45.94%) while that was higher in bd-878 (22.74%). stress condition caused significant decrease in plant growth. these results were in harmony with abass and mohamed (2011) who reported that the plant growth parameters of common bean (shoot and root length, fresh and dry weights of shoots and roots) decreased significantly with increasing drought stress as compared with control plants. such decline in shoot and root growth in response to stress might be due to either decrease in cell elongation, cell turgor, cell volume and eventually cell growth (banon ​et al.​, 2006), and/or due to blocking up of xylem and phloem vessels thus hindering any translocation through (lavisolo and schuber, 1998). physiological basis of salinity tolerance in foxtail millet 15 leaf water content the effect of salt stress on leaf water was statistically significant (figure 1). at 60 mm saline condition relative (per cent of control) leaf water of the genotypes ranged from 69% to 87%. highest relative leaf water was obtained from genotype bd-878 (87%), followed by bari kaon-1 (79%), and bd-881 (78%) and it was lowest in bd-897 (69%). at 120 mm saline condition relative (per cent of control) leaf water content of the genotypes ranged from 63% to 84%. highest relative leaf water was obtained from genotype bd-878 (84%), followed by bari-kaon-1 (75%) and bd-881 (68%) and it was lowest in bd-897 (63%). the reduction in leaf rwc (%) was provoked by the water deficiency in soil, in which the water stress due to salinity effect simulated artificially in this experiment cause as direct consequence changes in lrwc, because during the transpiration process and photosynthesis occur water loss through of the stomata and the assimilation / reposition rate is strongly affected, occurred probably decrease of the conductance stomatal for reduce the water loss to the atmosphere (verslues ​et al., ​2006​). velu and palanisami (2001) also reported that water stress significantly reduced relative water content of the plant. fig. 1. relative leaf water content of four foxtail millet genotypes as affected by salinity. chlorophyll a the effect of salt stress on chlorophyll content was statistically significant (figure 2). at 60 mm saline condition relative (per cent of control) leaf water of the genotypes ranged from 69% to 85%. highest relative chlorophyll a content was obtained from genotype bari kaon-1 (85%), followed by bd-878 (82%) and bd-881 (75%) and it was lowest in bd-897 (69%). at 120 mm saline condition relative (per cent of control) chlorophyll a content of the genotypes ranged from 60% to 75%. highest relative leaf water was obtained from genotype bd-878 (75%), followed by bari-kaon-1 (70%) and bd-897 (61%).and it was lowest in bd-881 (60%). 16 akter et al. fig. 2. relative chlorophyll a content of four foxtail millet genotypes as affected by salinity. chlorophyll b the effect of salt stress on chlorophyll b was statistically significant (figure 3). at 60 mm saline condition relative (per cent of control) chlorophyll b content of the genotypes ranged from 47% to 78%. highest relative leaf water was obtained from genotype bd-878 (78%), followed by bd-881 (76%), bd-897 (60%) and it was lowest in bari kaon-1 (47%). at 120 mm saline condition relative (per cent of control) chlorophyll b content of the genotypes ranged from 24% to 63%. highest relative leaf water was obtained from genotype bd-878 (63%), followed by bd-881 (57%), bd-897 (57%) and it was lowest in bari-kaon-1 (24%). fig. 3. relative chlorophyll b content of four foxtail millet genotypes as affected by salinity. physiological basis of salinity tolerance in foxtail millet 17 total chlorophyll content the effect of salt stress on total chlorophyll content was statistically significant (figure 4). at 60 mm saline condition relative (per cent of control) total chlorophyll content of the genotypes ranged from 61% to 80%. highest relative total chlorophyll was obtained from genotype bd-878 (80%), followed by bd-881 (75%) and bd-881 (75%) and it was lowest in bd-897 (66%) bari kaon-1 (61%), at 120 mm saline condition relative (per cent of control) leaf chlorophyll content of the genotypes ranged from 41% to 70%. highest relative leaf total chlorophyll was obtained from genotype bd-878 (70%), followed by bd-897 (60%) and bd-881 (59%) and it was lowest in bari-kaon-1 (41%). the reduction of the total chlorophyll due to salt stress was lower in bd-878 (30%), while that was higher in bari kaon-1 (59%). abass and mohamed (2011) who reported that photosynthetic pigments contents in leaves of common bean plants were highly significantly decreased with increasing the level of drought stress. sairam ​et al​. (2002) showed higher decrease in pigment contents of wheat genotypes under salinity at the three stages. the observed decrease of chlorophyll content in the plants grown under saline conditions may be attributed to both of the increased degradation and the inhibited synthesis of that pigment (garsia ​et al.​, 2002). the reduction in chlorophyll content under stress has been considered a typical symptom of oxidative stress and may be the result of pigment photo-oxidation and chlorophyll degradation. the decrease in the photosynthetic activity under stress may be due to stomatal or non-stomatal mechanisms. stomata closure is one of the first responses to drought stress which result in declined rate of photosynthesis. the drought induced reduction in the chlorophyll content could be attributed to loss of chloroplast membranes, excessive swelling, and distortion of the lamellae vesiculation and the appearance of lipid droplets. it was also reported that this pigment was sensitive to increasing environmental stress (terzi ​et al.​, 2010). the decrease in total chlorophyll content may have resulted from a decrease in leaf water status in the soybean. 18 akter et al. fig. 4. relative total chlorophyll content of four foxtail millet genotypes as affected by salinity. proline content the effect of salt stress on proline content was statistically significant (figure 5). at 60 mm saline condition relative (per cent of control) proline content of the genotypes ranged from 124% to 157%. highest relative proline content was obtained from genotype bd-878 (157%), followed by bari kaon-1 (135%), and bd-897 (129%) and it was lowest in bd-881 (124%). at 120 mm saline condition relative (per cent of control) proline content of the genotypes ranged from 157% to 179%. highest relative proline content was obtained from genotype bd-878 (179%), followed by bari-kaon-1 (164%) and bd-897 (161%) and it was lowest in bd-881 (157%). the proline accumulation is a metabolic response characteristic of plants under abiotic stresses, it being showed the increase in this experiment because the free proline work as osmotic adjustor that objective reduce the negative effects provoked in the plants under adverse conditions zhu (2002). fig. 5. relative proline content of four foxtail millet genotypes as affected by salinity proline is known to play as an osmoprotectant in plants subjected to osmotic stresses resulted from drought and soil salinity. a positive correlation between proline accumulation and osmoticstress tolerance has been reported by muthulakshmi ​et al. (2013), abraham ​et al​. (2003), abdelhamid ​et al. (2013), khattab (2007), amirjani (2010), sadak and dawood (2014) and taie ​et al. (2013). remarkable increase in proline content under stress conditions could be due to changes in proline metabolism profile under salinity stress, with an increased expression of proline synthetic enzymes and breakdown of proline-rich protein (tewari and singh, 1991). according to kaouther ​et al​. (2012) investigations with chili pepper (​capsicum frutescens ) obtained results showing significant increase in proline in all cultivars with the physiological basis of salinity tolerance in foxtail millet 19 increase of salt concentration in irrigation water. the accumulation of osmolyte compounds is often proposed as a solution to overcoming the negative consequences of water deficits in crop production which has been proposed as an adaptive mechanism for drought and salt tolerance. indeed, osmolyte accumulation (oa) in plant cell results in a decrease of the cell osmotic potential and help in the maintenance of water absorption and cell turgor pressure, which might contribute to sustaining physiological processes, such as stomatal opening, photosynthesis and expansion growth (kaouther ​et al​., 2012). malondialdehyde (mda) content the effect of salt stress on melondialdehyde (mda) content was statistically significant (figure 6). at 60 mm saline condition relative (per cent of control) mda content of the genotypes ranged from 106% to 116%. highest relative mda content was obtained from genotype bd-881 (116%) followed by bd-897 (114%), and bari kaon-1 (112%) and it was lowest in bd-878 (106%). at 120 mm saline condition relative (per cent of control) mda content of the genotypes ranged from 107% to 119%. highest relative mda content was obtained from genotype bd-881 (119%), followed by bari-kaon-1 (116%), and bd-897 (110%) and it was lowest in bd-878 (106%). the relative mda content was significantly higher in saline condition than control in all the genotypes. the rise in mda content under stress conditions suggests that water/saline stress could induce membrane lipid peroxidation by means of ros (sairam ​et al., 2002). ​it is also generally accepted that the accumulation of mda, a measure of lipid peroxidation, is considered a potential marker of oxidative damage (jouve ​et al.​, 2003; ashraf, 2009; ashraf ​et al​., 2010). generally, mda concentration changes with increasing salt concentration e.g. in limonium bicolor, it decreased at 100 mm, while increased at 200 mm nacl indicating that l. bicolor plants were better protected from oxidative damage under saline regime (li, 2008). in the present investigation, the lower relative values of mda in bd-878 indicate that at cellular level this genotype is better equipped with efficient free radical quenching system that offers protection against oxidative stress. 20 akter et al. fig. 6. relative melondialdehyde content of four foxtail millet genotypes as affected by salinity. effect of salt stress on yield and yield contributing characters number of tiller the effect of salt stress on number of tiller/plant was statistically significant (table 3). at control condition, the tiller number was the highest in bd-878 (12.33), followed by bd-881 (9.33), bd-897 (9.00), while the lowest was in bari kaon-1 (8.67). at 60 mm saline condition the highest tiller number was recorded with bd-878 (10.33) and the lowest was in bbari kaon-1 (7.00). relative (per cent of control) tiller number of the genotypes ranged from 78.57% to 83.78%. highest relative tiller number was obtained from genotype bd-878 (83.78%), followed by bd-897 (81.48%), and bari kaon-1 (80.77%) and it was lowest in bd-881 (78.57%). at 120 mm saline condition the highest tiller number was recorded with bd-878 (7.00) and the lowest was in bd-881 (4.48)​. relative (per cent of control) tiller number of the genotypes ranged from 48.01% to 67.74%. highest relative tiller number was obtained from genotype bd-878 (67.74%), followed by bari-kaon-1 (57.69%) and bd-897 (55.56%) and it was lowest in bd-881 (48.01%). tiller number reduction due to salinity was lower in bd-881 (32.26%) while that was higher in bd-878 (51.99%). table 3. tiller number and panicle number of foxtail millet genotypes as affected by salinity genotypes tiller number plant​-1 panicle number-plant​-1 control 60 mm salinity 120 mm salinity control 60 mm salinity 120 mm salinity bd881 9.33 7.33 (78.57) 4.48 (48.01) 9.33 7.33 (78.57) 5.00 (53.57) physiological basis of salinity tolerance in foxtail millet 21 bd897 9.00 7.33 (81.48) 5.00 (55.56) 8.67 6.33 (73.08) 5.00 (57.69) bd878 12.33 10.33 (83.78) 7.00 (67.74) 8.00 7.00 (87.50) 6.00 (85.71) bari kaon-1 8.67 7.00 (80.74) 5.00 (57.69) 5.67 4.33 (76.47) 3.67 (64.71) lsd​(0.05) 2.61 2.13 cv (%) 20.0 20.0 values in parenthesis indicates percent of control number of panicle the effect of salt stress on number of panicle/plant was statistically significant (table 3). at control condition, the panicle number was the highest in bd-881 (9.33), followed by bd-897 (8.67), bd-878 (8.00), while the lowest was in bari kaon-1 (5.67). at 60 mm saline condition the highest panicle number was recorded with bd-878 (7.33) and the lowest was in bbari kaon-1 (4.33). relative (per cent of control) panicle number of the genotypes ranged from 73.08% to 87.50%. highest relative panicle number was obtained from genotype bd-878 (87.50%), followed by bd-881 (78.57%) and bari kaon-1 (76.47), and the lowest was in bd-897(73.08). at 120 mm saline condition the highest panicle number was recorded with bd-878 (6.00) and the lowest was in bari-kaon-1 (3.67). relative (per cent of control) panicle number of the genotypes ranged from 53.57% to 85.71%. highest relative panicle number was obtained from genotype bd-878 (85.71%), followed by bari-kaon-1 (64.71%) and bd-897 (57.69%) and it was lowest in bd-881 (53.57%). panicle number reduction due to salinity was lower in bd-881 (14.29%) while that was higher in bd-878 (46.43%). panicle weight the effect of salt stress on panicle weight (g/plant) was statistically significant (table 4). at control condition, the panicle weight was the highest in bari kaon-1 (8.00), followed by bd-878 (4.94), bd-897 (7.46), and the lowest was in bd-881 (4.44). at 60 mm saline condition the highest panicle weight was recorded with bari kaon-1 (5.59) and the lowest was in bd-881 (3.12). relative (per cent of control) panicle weight of the genotypes ranged from 42.78% to 85.48%. highest relative panicle weight was obtained from genotype bd-878 (85.48%), followed by bd-881 (70.26%), and bari-kaon-1. (69.86%) and it was lowest in bd-897 (42.78%). at 120 mm saline condition the highest panicle weight was recorded with bari-kaon-1 (2.34) and the lowest was in bd-881 (1.92). relative (per cent of control) panicle weight of the genotypes ranged from 27.71% to 54.05%. highest relative panicle weight was obtained from genotype bd-878 (54.05%), followed by bd-881 (43.29%) and bari-kaon-1(29.25) and it was lowest in bd-897 (27.71%). panicle weight reduction due to salinity was lower in bd-878 (45.95%) while that was higher in bd-897 (72.29%). seed yield the effect of salt stress on seed yield (g/plant) was statistically significant (table 4). at control condition, the seed yield was the highest in bd-897 (11.71), followed by bd-878 (9.51), bari kaon-1 (9.19), and the lowest was in bd-881 (9.10). at 60 mm saline condition the highest seed yield was recorded with bd-878 (7.60) and the lowest was in bd-897 (3.83). relative (per cent of control) seed yield of the genotypes ranged from 32.68% to 79.86%. highest relative seed yield was obtained from genotype bd-878 (79.86%), followed by bari kaon-1 22 akter et al. (67.30%) and bd-881 (59.08%) and it was lowest in bd-897 (32.68%). at 120 mm saline condition the highest seed yield was recorded with bd-897 (3.30) and the lowest was in bd-881 (1.01). relative (per cent of control) seed yield of the genotypes ranged from 11.13% to 28.21%. highest relative seed yield was obtained from genotype bd-897 (28.21%), followed by bd-878 (20.45%) and bari-kaon-1 (12.77%) and it was lowest in bd-881 (11.13%). seed yield reduction due to salinity was lower in bd897 (71.79%), while that was higher in bd-881 (88.87%). salinity induced yield reduction has been reported in many crop species, which depends upon the severity and duration of the stress period. salinity was also found to reduce the shoot length, number and size of spikes and the grain yield (hendawy ​et al​., 2012). table 4. panicle weight and seed yield of foxtail millet genotypes as affected by salinity genotypes panicle weight (g plant​-1​) seed yield (g plant​-1​) control 60 mm salinity 120 mm salinity control 60 mm salinity 120 mm salinity bd881 4.44 3.12 (70.26) 1.92 (43.29) 9.10 5.37 (59.08) 1.01 (11.13) bd897 7.46 3.19 (42.78) 2.07 (27.71) 11.71 3.83 (32.68) 3.30 (28.21) bd878 4.94 4.22 (85.48) 2.28 (54.05) 9.51 7.60 (79.86) 1.55 (20.45) bari kaon-1 8.00 5.59 (69.86) 2.34 (29.25) 9.19 6.19 (67.30) 1.17 (12.77) lsd​(0.05) 2.18 4.00 cv (%) 11.4 10.1 values in parenthesis indicates percent of control saline water irrigations with salinity increasing from 1 to 16 ds m​-1 had been noticed to linearly decrease seed and straw yield, harvest index and 1000 grain weights in foxtail millet and the harvested seeds from these treatments were found to germinate into normal seedlings (thimmaiah ​et al​., 1989). in the present study, the reduction in seed yield under salt stress was associated with dramatic decrease in all these yield components. conclusion based on the above results it may be concluded that bd-878 showed relatively higher salinity tolerance in respect of dry matter 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jasminedaisy.bari@gmail.com (received: 03 october 2022, accepted: 13 april 2023) keywords: chilli, legume vegetable, intercropping, chilli equivalent yield, benefit cost ratio abstract the field experiment was carried out on chilli legume vegetables intercropping system using five treatments at the agronomy research field of bangladesh agricultural research institute, gazipur during rabi season, 2019-2020 and 20202021. the study was conducted to find out the suitable intercrop combination for higher productivity and economic return. the treatments were viz., t1= sole chilli (60 cm × 50 cm), t2 = chilli (100%) + one row bush bean (50%), t3= chilli (100%) + two row bush bean (100%), t4= chilli (100%) + one row pea (50%), t5= chilli (100%) + two row pea (100%). significantly the highest yield (8.67 t/ha) was obtained in sole chilli. but chilli + one inter row pea intercropping system gave the highest chilli equivalent yield (21.47 t/ha). the highest gross margin (tk. 151896/ha) and bcr (3.42) were obtained from the same treatment. the results revealed that one row pea (50%) intercropped with chilli (100%) might be suitable intercrop combination for higher productivity and economic return. introduction intercropping system is an important feature of tropical agriculture which could be a viable option to increase productivity of crops per unit area and per unit time. intercropping is a crop management system involving growing of two or more dissimilar crops simultaneously on the same land area. it involves crop intensification in respect to both time and space dimensions (ahlawat and sharma, 2002) and increases total productivity through efficient utilization of land, labour, growth resources such as solar radiation and different inputs including fertilizer and water. it is a cropping system which integrates crop production with soil conservation. intercropping is an excellent technique to increase total productivity (islam et al., 2010), monetary return (begum et al., 2010) and resource use efficiency (islam et al., 2006) as well as to fulfill the diversified need of farmers (akhteruzzaman et al., 2008). moreover, it provides several major advantages namely; diversification reduces risk associated with crop failure, offers greater yield stability and utilizes the available growth resources more efficiently and sustainably (islam et al., 2006). the use of early maturing crop varieties, row arrangement, spacing and plant population are some important methods that help increase the yield of intercrop (rahman et al., 2009). better intercrop production could be achieved with the choice of the appropriate crops (santalla et al., 2001), population density and planting geometry of component crops (myaka 1995). benefits of intercropping may be briefed as: better use of resources, improvement of soil fertility by legume components of the system, soil preservation through covering the bare land between the rows, reduction of biotic and abiotic risks by increasing diversity, suppression of weed infestation etc. (van wolfswinkel, 2012). another advantage of mixing crop is the yield and quality improvement compared with sole cropping. the most 52 chowdhury et al. common crop combination in tropical intercropping systems is mixture of legumes and nonlegumes (wood and mayers 1987; fujita et al., 1990). inclusion of legumes enhances crop and nitrogen yields of the non-legumes (baker and blamey, 1985; wood and mayers, 1987). chilli is one of the major spices crops in bangladesh cultivated in 2, 49,748 acres of land (both winter and summer) with a production of 492000 metric tons (bbs, 2021). it is usually grown as sole and in some cases as intercrop in various parts of bangladesh. chilli is generally grown with wide row spacing about 60 cm, which makes it suitable for intercropping. intercropping of chilli with different vegetables offer greater scope to utilize the land and other resources to the maximum extent. productivity of the system can be enhanced by judicious selection of vegetables differing in duration and growth rhythms, so as to adjust the demand for the above and underground resources (suresha et al., 2007). so, in the inter-row space of chilli, legume crop such as french bean or pea can be introduced as intercrop for higher economic return as well as incorporated plant biomass can be improved soil nutritious status. therefore, this experiment was conducted to find out suitable legume vegetable species to grow as an intercrop with chilli for higher productivity and economic return. materials and methods a field experiment was conducted under irrigated condition during rabi season, 2019-2020 and 2020-2021 at the agronomy research field of bari, gazipur (23°53'-24°21'n latitudes and 90°09'-92°39'e longitudes). gazipur located at an elevation of 14 meters (45.93 feet) above sea level, a tropical wet and dry or savanna climate (classification: aw). the district’s yearly temperature is 28.95ºc (84.11ºf) and it is 1.21% higher than bangladesh’s averages. gazipur typically receives about 71.24 millimeters (2.8 inches) of precipitation and has 115.47 rainy days (31.64% of the time) annually. the soil of research area belongs to the chhihata series under aez-28. the soil was silty clay loam with ph 6.23, om 1.29% (very low), total n 0.112% (very low), exchangeable k 0.098 meq/100g soil (very low), available p 15.23μg/ml (optimum), available s 24.94 µg/g (optimum), available zn 0.654 µg/g (low) and available b 0.168 µg/g (very low). organic matter, n, k and b were under critical level in the soil. the experiment consisted of five different treatments viz., t1= sole chilli (60 cm × 50 cm), t2= chilli (100%) + one row bush bean (50%), t3= chilli (100%) + two row bush bean (100%), t4= chilli (100%) + one row pea (50%), t5= chilli (100%) + two row pea (100%). experiment was laid out in a randomized complete block design (rcbd) with three replications and each gross plot was of size 3.6 × 3.0 m2. bushbean (var. bari jharsheem-2) and pea (var. bari motorsuti3) were used as intercrop. chilli cv. bari morich-3 was transplanted with 2 seedlings per hill and later maintained one seedling per hill. the inter row spacing was 60 cm and intra row spacing was 50 cm. intercrops were sown between the rows. five tons of cowdung per ha was applied to the crop before transplanting. basal dose of fertilizer was applied @ 96-45-75-151.5-1.4 kg/ha n p k s zn b (frg, 2018). half of n and all other fertilizers were applied as basal during final land preparation. remaining n was applied in three equal splits at 25, 50 and 70 dat in chilli as ring method. under intercropping situation no additional fertilizer was applied. chemical fertilizers were used in the form of urea, triple super phosphate, muriate of potash, gypsum, zinc sulphate and boric acid. thirty days old seedling of chilli was transplanted on 21 november 2019 and 18 november 2020, respectively and intercrops were sown 10 days after planting of chilli in line according to the treatment combinations. intercultural operations and plant protection measures were taken up as and when required. first harvesting of chilli was done at 120 dap (days after planting) in 2020.and 118 dap in 2021 and harvesting was continued up to 196 dap in 2020 and 200 dap in 2021. french bean was harvested three comparative productivity and profitability of chilli-legume vegetable intercropping systems 53 times at 73, 78 and 85 das in 2020 and 75, 80 and 86 das in 2021. pea was harvested on 10 january 2020 and 8 january 2021. observations were taken on five randomly selected plants in each plot in respect to plant height, number of chilli fruits/plant, weight of chilli fruit, number of pods, pod length, single plant pod weight and yield. for economic analysis, gross income, total operational cost, gross margins and bcr were calculated. data on yield and yield contributing characters were taken and statistically analyzed following mstat-c software package. means were adjudged by lsd test at 5% level of significance. chilli equivalent yields (cey) were computed by converting yield of intercrops on the basis of prevailing market price of the individuals by using the formula of bandyopadhayay (1984). chilli equivalent yield (cey) = yield of component crop + where, yi = yield of component crop (pea/bushbean) in intercropping pi = price of component crop (pea/bushbean) in intercropping results and discussion yield and yield contributing characters of chilli the growth of chilli was found to be affected by the intercrops. the two years pooled yield and yield attributes data of chilli have been presented in table 1. the plant height was significantly lower in all the treatments than the sole (table 1). the plant height was comparatively higher in sole chilli (90.40 cm) and the lowest (61.15 cm) was recorded when two row bushbean intercropped with chilli at harvest. this might be due to insufficient nutrient uptake through competition in this intercropping system. similar results were also obtained by ahmed et al. (2018). the number of fruit/plant and weight of fruit/plant differed significantly due to influence exerted by different treatments. the maximum number of fruits/plant (232) and highest weight of fruit/plant (320.46 g) were observed in sole chilli, while the lowest number of fruits/plant (168) and weight of fruit/plant (186.44 g) were observed in chilli + two inter row bushbean intercropping. in sole chilli, the values of these parameters were more might be due to the utilization of wider space and less compitition for natural resources. similar results were observed by begum et al. (2015). yield of chilli varied from 6.72 t/ha to 8.67 t/ha due to influence exerted by different treatments. among the treatment combinations sole chilli gave the highest yield of 8.67 t/ha. among the intercropping systems, the highest chilli yield was recorded in chilli + single row pea cropping (8.57 t/ha) might be due to less competition for different growth resources. chilli yield was the lowest (6.72 t/ha) in the chilli + two inter row bushbean treatment, might be due to the large canopy of french bean which hampered the growth and yield of chilli. similarly, varghese et al. (1979) reported the negative effects of intercropping on yield of cabbage. islam et al. (2006) and santalla et al. (2001) also reported that seed yield was higher in monoculture as compared to their corresponding intercropped yield. the yield loss due to intercropping also reported by ahmed et al. (2013), muoneke and ndukwe (2008) and manga et al. (2003). intercropping system also significantly reduced chilli yield by 1 to 23% over sole chilli (table 1) might be due to inter-specific competition for space, solar radiation, nutrients and water. chilli + two row bush bean intercropping system reduced 23% chilli yield followed by chilli + two row pea (19%) while the minimum yield loss of chilli was found in chilli + one row pea (1%) followed by chilli + one row bush bean (4%) combinations. the yield loss due to intercropping also reported by ahmed et al. (2013). 54 chowdhury et al. table 1. crop characters and yield of chilli as influenced by different intercropping (pooled of 2019-2020 and 2020-2021) treatments plant height (cm) fruits/plant (no.) fruit weight/ plant (g) chilli yield (t/ha) intercropped chilli yield decreases over sole chilli (%) sole chilli (60 cm × 50 cm) 90.40 232 320.46 8.67 chilli (100%)+one row bush bean (50%) 72.15 196 255.65 8.31 4 chilli (100%)+two row bush bean(100%) 61.15 168 186.44 6.72 23 chilli (100%) + one row pea (50%) 78.70 215 229.55 8.57 1 chilli (100%) + two row pea (100%) 65.85 186 212.93 7.06 19 lsd(0.05) 13.56 11.11 77.05 0.22 cv (%) 6.49 4.55 3.89 2.29 yield of legume vegetables the two years pooled yield of pea and bush bean have been presented in table 2. the yield of pea and bush bean was significantly influenced by intercropped with chilli. among the intercropping combinations the higher yield of bushbean (11.15 t/ha) was recorded in t3 treatment (chilli 100% + two row bush bean 100%) and the lowest bushbean yield (8.17 t/ha) from t2 treatment (chilli 100% + one row bush bean 50%). this might be due to higher plant population in t3 treatment. in case of pea the similar trend also observed due to similar cause. the higher pea yield (7.14 t/ha) was recorded in t5 treatment (chilli 100% + two row pea 100%) and the lowest pea yield (6.45 t/ha) was obtained from t4 treatment (chilli 100% + one row pea 50%). ahmed et al., (2006) also reported similar result. table 2. yield of legume vegetables as influenced by intercropping (pooled of 2019-2020 and 2020-2021) treatments yield (t/ha) chilli (100%) + one row bush bean (50%) 8.17 chilli (100%) + two row bush bean (100%) 11.15 chilli (100%) + one row pea (50%) 6.45 chilli (100%) + two row pea (100%) 7.14 lsd(0.05) 1.57 cv (%) 3.89 equivalent yield and cost and return analysis total productivity of system was expressed in chilli equivalent yield (cey). chilli equivalent yield (cey) and cost benefit analysis data are presented in table 3. the chilli equivalent yield was influenced in response to different intercropping systems (figure 2). all intercropping gave higher cey than sole chilli indicating higher productivity than sole cropping. among those, the highest cey (21.47 t/ha) was observed in chilli + one row intercrop pea combination followed by t5 combination (21.34 t/ha) and the lowest (8.67 t/ha) was observed in sole chilli. maximum cey in aforesaid combination was observed due to additional yield of component crop. further, economics of different chilli intercropping system was analyzed taking into account the prices prevailed at local market. though, the sole chilli gave significantly the highest yield per ha but gross return and gross margin/ha were highest in all intercropped treatments because of higher cye. considering the economics of intercropping in chilli, chilli + one interrow pea was found to be the best with highest gross return (tk. 214700/ha) and gross margin (tk. 151896/ha) comparative productivity and profitability of chilli-legume vegetable intercropping systems 55 where as next best treatment was chilli + two inter row pea (tk. 213400/ha and tk. 150449/ha respectively. the highest bcr (3.42) was observed in chilli + one row intercrop pea intercropping system followed by chilli + two rows inter crop pea (3.39). cost of production of all intercropping systems was more than sole chilli because of the involvement of higher seed cost as well as cost of more labours engaged in different operations. chilli + legume intercropping system increased total productivity by 90 -148% over sole chilli (table 3). among the treatments, cey in chilli + one row pea combination was 148% higher over the sole chill and lowest in chilli + one row bush bean. similar results were also reported by begum et al. (2015) in chilli + root crop intercropping systems. table 3. chilli equivalent yield and economics of different chilli intercropping (pooled of 20192020 and 2020-2021) treatments chilli equivalent yield (t/ha) % increase cey over sole chilli gross return (tk/ha) cost of cultivation (tk/ha) gross margin (tk/ha) bcr t1 8.67 86700 57000 29700 1.52 t2 16.48 90 164900 62280 102620 2.65 t3 17.87 106 178700 62876 115824 2.84 t4 21.47 148 214700 62804 151896 3.42 t5 21.34 146 213400 62951 150449 3.39 market price (tk./kg): chilli= 10, bushbean= 10, pea= 20 t1= sole chilli (60 cm × 50 cm), t2 = chilli (100%) + one row bush bean (50%), t3= chilli (100%) + two row bush bean (100%), t4= chilli (100%) + one row pea (50%), t5= chilli (100%) + two row pea (100%). conclusion it can be concluded that chilli intercropped with bushbean or pea produced higher yield than sole chilli. all studied combinations can be cultivated for higher productivity but chilli (100 %) + one row of pea (50%) in between chilli lines combination could be more suitable combination for higher productivity and profitability of intercrop, reference ahlawat, i.p.s. and r.p. sharma. 2002. agronomic terminology. indian society of agronomy, division of agronomy, indian agricultural research institute, new delhi, india. ahmed, f., m.n. islam, m.s. alom, m.a.i. sarkar and m.a. mannaf. 2013. study on intercropping leafy vegetables with okra (abelmoschus esculentus l.). bangladesh j. agril. res. 38(1): 137143. akhetruzzaman, m., m.n. islam, b.l. nag and m.t. rahman. 2008. productivity of potato-hybrid maize relay cropping under different fertilizer levels. eco-friendly agril. j. 1(5): 300-303. baker, c.m. and f.p.c. blamey. 1985. nitrogen fertilizer effects on yield and nitrogen uptake of sorghum and soybean grown in sole cropping and intercropping system. field crop res. 12: 233-240. begum, s.a., m.s. zaman and a.s.m.m. rahman khan. 2015. intercropping of root crops with chilli in charlands of mymensingh. progres. agric. 26: 109-114. begum, s., m.n. islam, m.t. rahaman, j.a. chowdhury and m.i. haque. 2010. suitability study of different chilli varieties for intercropping with sweet gourd. expt. biosci. 1(2): 1-4. 56 chowdhury et al. frg (fertilizer recommendation guide). 2018. bangladesh agricultural research council (barc), farm gate, dhaka 1215. 223p. fujita, k., s. ogata, k. matsumoto, t. masuda, g.k.o. budu and k. kuwata. 1990. nitrogen transfer and dry matter production in soybean and sorghum mixed cropping system at different population densities. soil sci. plant nutr. 36(2): 233-241. islam, m.n., m.a.i. sarker, m.k. islam, s. begum and m.a. mannaf. 2010. intercropping of brinjal with chilli under different planting geometry for higher productivity and return. j. expt. biosci. 1(2): 51-55. islam, m.n., m.m. haque and a. hamid. 2006. planting arrangement and population density effect on the physiological attributes and productivity of maize-bushbean intercropping system. bangladesh 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system. karnataka j. agric. sci. 20(4): 807-809. van wolfswinkel, m. 2012. intercropping of annual foodcrops. from: www.allindiary.org. accessed: feb. 2nd. varghese, l., s.b. umale and m.p. kawthalkar. 1979. effect of intercrops on the growth and yield of cabbage. south indian hort. 38: 196-198. wood, i.m. and r.j.k. myers. 1987. food legumes in farming systems in the tropics and subtropics. in: wallis es, byth de (eds.) food legume improvement for asian farming systems. aciar, canberra, pp. 34–45. bangladesh agron. j. 2022, 25(2): 43-49 growth and yield performance of aus rice under agronomic managements m.h. mahmud1, p.k. biswas2, m.s. islam2 and m.d. hossain3 1project implementation unit-barc, national agricultural technology program-phase-ii project, barc, dhaka1215, 2department of agronomy, sau dhaka-1207, bangladesh, 3farm superintendent, bangladesh wheat and maize research institute, regional, station, jamalpur corresponding e-mail: h.mahmud193@gmail.com (received: 02 august 2022, accepted: 22 december 2022) keywords: agronomic management, growth, yield, aus rice abstract the experiment was conducted at the experimental field of sher-e-bangla agricultural university, dhaka during the period from march to june, 2018 to study the effects of agronomic managements on growth and yield of aus rice. the experiment comprised of split –plot design where varieties in the main plots viz., i) brri dhan65 (v1) and ii) nerica (v2) and five agronomic managements in the subplots viz., i) no management-m0, ii) no weeding, but all other managements-m1, iii) no fertilizer application, but all other managements-m2, iv) no irrigation application, but all other managements-m3 and v) recommended management-m4, respectively. almost all the studied characters were found statistically significant due to variation in treatments. significant variation was recorded different yield contributing characters and yield of aus rice. at 30, 50, 70 das and harvest, the taller plant (24.61 cm, 41.27 cm, 60.23 cm and 80.28 cm, respectively), grain yield (0.96 t ha-1) and straw yields (2.75 t ha-1) were recorded from v2 compared to that of v1. similarly, the tallest plant (27.11 cm, 49.66 cm, 71.49 cm and 91.07 cm at 30, 50, 70 das and harvest, respectively), grain yield (2.34 t ha-1) and straw yield (5.30 t ha-1) were observed from m4. in respect of interaction, the highest grain yield (2.43 t ha-1) and straw yield (5.31 t ha-1) were observed from v1m4 (brri dhan65 with recommended management), while the lowest grain yield (0.12 t ha-1) from v1m0 (brri dhan65 with no management) and straw yield (0.85 t ha -1) from v2m0 (nerica with no management). irrespective of variety with no management reduced 94-95% grain yield of aus rice that was 84-89% for no weeding and no fertilizer application. introduction rice (oryza sativa l.) is the most important food in tropical and subtropical regions (singh et al., 2012). it is the staple food of more than three billion people in the world, most of who live in asia (irri, 2009). it is the driving force of bangladesh agriculture covers about two-thirds of the cultivated land and constitutes 90% of the food grain production in bangladesh (bbs, 2020). in bangladesh, the geographical, climatic and edaphic conditions are favorable for year-round rice cultivation. rice yields are either decelerating/stagnating/declining in post green revolution era mainly due to imbalance in fertilizer use, soil degradation, irrigation and weeding schedule, type of cropping system practiced lack of suitable rice genotypes/variety for low moisture adaptability and disease resistance (prakash, 2010). the average yield of rice in bangladesh is about 3.07 t ha-1 (bbs, 2018). 44 mahmud et al. appropriate agronomic management practices greatly influence the growth and yield of rice. yield loss is occurred due to improper weeds, nutrient management and irrigation schedule. therefore, these managements are a complete package for satisfactory any crop production specially rice production in bangladesh. weed free condition during the critical period of competition, recommendation doses of fertilizer application and appropriate amount of water are essential for obtaining optimum rice yield. subsistence farmers in bangladesh spend more time and energy on control of weeds; do not give proper dose of fertilizer and optimum amount of water for rice cultivation. thus, the appropriate agronomic management practices need to be adopted by the farmers for maximizing rice yield. the present research work was, therefore, undertaken to find out the effect of agronomic management on growth and yield of aus rice. materials and methods the experiment was conducted at experimental field of sher-e-bangla agricultural university (2377n latitude and 9033e longitude) which belongs to the agro-ecological zone of the modhupur tract, aez-28 (anonymous, 1988). the soil of the experimental field classified as deep red brown terrace soils in bangladesh soil classification system (undp and fao, 1988). split -plot design with three replications was followed where variety in the main plots and agronomic managements in the sub-plots. there were 10 plots of size 5.0 m × 2.0 m in each of 3 replications. there were two rice varieties viz. nerica (v1) and brri dhan65 (v2) and five agronomic managements viz. (no management-m0, no weeding, but all other managements-m1, no fertilizer application, but all other managements-m2, no irrigation application, but all other managements-m3, and recommended management-m4. seeds were sown in line in main plot after good tilt of land. the experimental area was fertilized with 120, 100, 80, 60 and 10 kg ha-1 of n, p2o5, k2o, s and zn. the entire amount of tsp, mop, gypsum and zinc sulphate were applied during the final preparation of land. half of urea was applied during final land preparation and rest half applied two equal installments at 30 das and 45 das. plant height, number of tillers hill-1 and number of leaves hill-1 were calculated from randomly pre-selected 5 hills plot-1. dry matter was recorded from the mean oven dry weight of plants from 2 hills plot-1. filled grains panicle-1 and unfilled grains panicle-1 were counted from the average number of grains from ten panicles.1000-grain weight was measured at 12% moisture content. grain yield and straw yield were determined and biological yield was calculated by summing up the grain and straw yield. harvest index refers to the ratio of economic yield to biological yield and was computed with following formula (gardner et al., 1985). all the data collected on different parameters were statistically analyzed by technique using mstatc computer package program and the mean differences were calculated using least significant difference (lsd) test at 5 % level of probability. results and discussion effect of variety plant height, number of leaves hill-1, dry matter weight hill-1 and length of panicle varied significantly and number of effective tillers hill-1 and number of non-effective tillers hill-1 statistically identical a (table 1). the higher plant height (80.28 cm) and panicle length (19.84 growth and yield performance of aus rice under agronomic managements 45 cm) was obtained from nerica whereas, the higher value of dry matter content hill-1 (8.78 g), number of effective tillers hill-1 (5.24) and number of non-effective tillers hill-1 (1.72) was found from the brri dhan65. due to genetic makeup of different varieties, plant height among the varieties might be varied (murshida et al., 2017). amin et al. (2006) revealed that the variation of dry matter among rice varieties. number of filled grains panicle-1 and number of total grains panicle-1 varied significantly where number of unfilled grains panicle-1, weight of 1000-grain, grain yield, straw yield and biological yield varied numerically for brri dhan65 and nerica (table 2). rice var. nerica produced better in all aspect of the yield and yield contributing characters viz. the number of filled grains panicle-1 (49.09), number of unfilled grains panicle-1 (27.25), weight of 1000-grain (22.51g), grain yield (0.96 t ha-1), straw yield (2.75 t ha-1), biological yield (3.71 t ha-1) and harvest index (21.52%) compared to brri dhan65. effect of agronomic management different agronomic managements showed significant differences on plant height, number of leaves hill-1, dry matter weight hill-1, number of effective tillers hill-1, and panicle length except number of non-effective tillers hill-1 (table 1). both recommended management (m4) and no irrigation but all other managements (m3) gave the highest plant (91.07 cm), dry matter content hill-1 (14.12 g) and panicle length (21.91 cm) and number of leaves hill-1 (61.13), number of effective tillers hill-1 (8.50) and non-effective tillers hill-1 (2.33) was found from recommended management (m4) individually. on the other hand, no management (m0) produced lowest in all growth parameters which are similar to no weeding. table 1. effect of variety and agronomic management on growth parameters of aus rice treatments plant height (cm) number of leaves hill-1 dry matter weight hill-1 (g) number of effective tillers hill-1 number of non-effective tillers hill-1 panicle length (cm) v1 71.80b 44.63a 8.78a 5.24 1.72 17.53b v2 80.28a 34.80b 8.31b 4.92 1.71 19.84a se (±) 0.99 1.98 0.99 ns ns 0.35 cv (%) 11.43 13.63 12.11 28.63 26.15 5.13 m0 60.31d 24.20d 4.55b 3.00c 1.00 15.41c m1 75.72b 38.30c 7.87b 3.50c 1.83 17.99b m2 66.77c 26.77d 5.39b 3.33c 1.83 17.57b m3 86.38a 48.17b 11.78a 7.00b 1.50 20.57a m4 91.07a 61.13a 14.12a 8.50a 2.33 21.91a se (±) 1.78 1.48 0.81 0.65 ns 0.73 cv (%) 14.52 9.14 13.21 21.55 27.83 6.72 brri dhan65 (v1), nerica (v2), no management -m0, no weeding but all other managements-m1, no fertilizer application but all other managements-m2, no irrigation but all other managements-m3, recommended management-m4, not significant –ns means with dissimilar letters are significantly different at p ≤ 0.05 at lsd test. different agronomic managements showed significant differences on yield and yield contributing characters (table 2). recommended management (m4) gave highest value in attributes of yield and yield contributing characters, whereas no irrigation but all other managements (m3) 46 mahmud et al. performed highest in number of unfilled grains panicle-1, and harvest index. lowest performance was obtained from no management (m0) and no weeding but all other managements (m1) in all parameters except in number of unfilled grains panicle-1 and weight of 1000grains for m1. no management reduced 94% grain yield of aus rice that followed by 87% for no weeding and 86% for no fertilizer application. without irrigation reduced 32% yield that might be due to the contribution of rainfall during the growing period. singh et al. (1999) reported that no weed management until maturity removed significantly higher amount of nitrogen through weeds (12.97 kg ha-1) and reduced the grain yield of rice by 49% compared to that of weed free crop up to 60 dat. table 2. effect of variety and agronomic management on yield and yield contributing characters of aus rice treatments number of filled grains panicle-1 number of unfilled grains panicle-1 weight of 1000 grains (g) grain yield (t ha-1) straw yield (t ha-1) biological yield (t ha-1) harvest index (%) variety v1 36.58b 23.71 22.02 0.95 2.67 3.63 19.45 v2 49.09a 27.25 22.51 0.96 2.75 3.71 21.52 se (±) 2.26 ns ns ns ns ns ns cv (%) 14.46 13.73 6.71 24.59 3.21 5.11 24.70 agronomic management m0 26.33c 19.33b 20.36c 0.14c 0.94c 1.08c 12.97c m1 27.83c 29.67a 21.96b 0.31c 1.45c 1.77c 12.90c m2 33.33c 19.67b 22.31b 0.33c 1.98c 2.29c 17.51b m3 55.33b 29.17a 23.11ab 1.62b 3.87b 5.48b 28.53a m4 71.67a 29.67a 23.56a 2.39a 5.30a 7.70a 30.51a se (±) 6.20 3.10 0.51 0.24 0.37 0.58 1.37 cv (%) 25.03 21.28 3.99 22. 08 18.32 17.24 11.61 brri dhan65 (v1), nerica (v2), no management -m0, no weeding but all other managements-m1, no fertilizer application but all other managements-m2, no irrigation but all other managements-m3, recommended management-m4, means with dissimilar letters are significantly different at p ≤ 0.05 at lsd test. interaction effect interaction effect of variety and agronomic managements showed significant differences on all growth characters (table 3). the tallest plant (94.48 cm) and panicle length (22.61 cm) were observed from the nerica with recommended management which are 50.61% and 37.44% higher than no management of same variety. the highest number of leaves hill-1 (70.40), dry matter content hill-1 (14.48 g), number of effective tillers hill-1 (9.33) and number of noneffective tillers hill-1 (2.67) showed 60.41, 71.75, 71.38 50.19 and 65.72%, respectively lower performance observed from brri dhan65 with recommended management than no management.no weeding, but all management also reduced 41.66, 55.73, 64.31, 37.45 and 57.16%, respectively lower performance of same parameters. suresh kumar et al. (2016) reviewed that weed flora under transplanted condition is very much diverse and consists of grasses, sedges and broad-leaved weeds causing yield reduction of rice crop up to 76 %. growth and yield performance of aus rice under agronomic managements 47 table 3. interaction effect of variety and agronomic management on growth parameters of aus rice at harvest treatments plant height (cm) number of leaves hill-1 dry matter weight hill-1 number of effective tillers hill-1 number of non-effective tillers hill-1 panicle length (cm) v1m0 57.88f 27.87e 4.09e 2.67d 1.33bc 14.36e v1m1 70.37d 41.07c 6.41cd 3.33d 1.67a-c 16.50d v1m2 61.11ef 30.40e 4.41de 3.00d 2.00ab 16.31d v1m3 82.03c 53.40b 11.46ab 7.67b 1.00bc 19.29c v1m4 87.66b 70.40a 14.48a 9.33a 2.67a 21.20b v2m0 62.73e 20.53f 5.02de 3.33d 0.67c 16.45d v2m1 81.07c 35.53d 7.33c 3.67d 2.00ab 19.47c v2m2 72.42d 23.13f 6.39cd 3.67d 1.67a-c 18.83c v2m3 90.73ab 42.93c 10.81b 6.33c 2.00ab 21.84ab v2m4 94.48a 51.87b 13.76ab 7.67b 2.00ab 22.61a se (±) 2.543 2.09 1.14 0.63 0.57 0.73 cv (%) 5.79 9.14 25.64 21.55 57.83 6.72 brri dhan65 (v1), nerica (v2), no management -m0, no weeding but all other managements-m1, no fertilizer application but all other managements-m2, no irrigation but all other managements-m3, recommended management-m4, means with dissimilar letters are significantly different at p ≤ 0.05 at lsd test. interaction effect of variety and agronomic managements showed significant differences on yield and yield contributing characters (table 4). the highest number of filled grains panicle-1, weight of 1000grain, grain yield, straw yield, biological yield and harvest index were observed from the recommended management both the varieties except in number of unfilled grains panicle-1 for nerica and weight of 1000 grain for brri dhan65. the lowest performance gave brri dhan65 with no management combination. nerica with no management reduced number of filled grains panicle-1 (56.25%), grain yield (93.64%), straw yield (83.75%) and biological yield (86.81%) and no weeding, but all management also reduced 58.93, 32.80, 83.90, 54.50 and 63.84%, respectively from recommended management. jayadeva et al. (2009) and subha and ramana (2009) found that hand weeding at 20 and 40 dat recorded highest plant height, dry matter production, tillers m-2, nutrient uptake by crop and highest grain and straw yield of rice crop. table 4. interaction effect of variety and agronomic management on yield and yield contributing characters of aus rice treatments number of filled grains panicle-1 number of unfilled grains panicle-1 weight of 1000 grains (g) grain yield (tha-1) straw yield (tha-1) biological yield (t ha-1) harvest index (%) v1m0 20.00e 17.00ef 20.78e 0.12c 1.03de 1.15d 10.74f v1m1 25.00de 22.33de 21.62d 0.23c 1.58d 1.82cd 12.28ef v1m2 22.00de 16.33f 22.19cd 0.27c 1.32de 1.59d 15.82d v1m3 47.67c 29.67bc 22.59c 1.70b 4.12b 5.82b 28.06b v1m4 68.67ab 33.33ab 22.89bc 2.43a 5.31a 7.74a 30.38ab v2m0 32.67d 21.67d-f 19.95e 0.15c 0.85e 1.01d 15.19d v2m1 30.67de 37.00a 22.30cd 0.38c 2.38c 2.77c 13.53de v2m2 44.67c 23.00d 22.42cd 0.38c 1.58d 1.96d 19.20c v2m3 63.00b 28.67bc 23.63ab 1.53b 3.62b 5.15b 29.01ab v2m4 74.67a 26.00cd 24.22a 2.36a 5.23a 7.66a 30.65a se (±) 4.20 3.13 0.51 0.237 0.365 0.576 1.373 cv (%) 20.03 16.28 3.99 22. 08 18.32 17.24 11.61 brri dhan65 (v1), nerica (v2), no management -m0, no weeding but all other managements-m1, no fertilizer application but all other managements-m2, no irrigation but all other managements-m3, recommended management-m4, means with dissimilar letters are significantly different at p ≤ 0.05 at lsd test. 48 mahmud et al. conclusion considering the above results, it may be concluded that agronomic management had significant role in the grain yield of rice. among the treatments, variety with recommended agronomic management (var. brri dhan66 with recommended practices) gave comparable higher grain yield closely followed by var. nerica with same management. however, further experimentation will need to be executed in different agro-ecological zones with more varieties of aus rice under agronomic management to reach a specific conclusion and 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136-138. bangladesh agron. j. 2022, 25(2): 19-29 polyethylene glycol mediated osmotic stress on germination, seedling traits and seed metabolic efficiency of wheat s.k. pramanik, s. sikder and m.a. hasan department of crop physiology and ecology, hajee mohammad danesh science and technology university, dinajpur-5200, bangladesh corresponding e-mail: pramaniksk100@gmail.com (received: 07 august 2022, accepted: 09 october 2022) keywords: polyethylene glycol, osmotic stress, germination, seedling growth, seed metabolic efficiency. abstract germination characteristics, early seedling growth and seed metabolic efficiency of four wheat genotypes (bari gom 28, bari gom 29, baw 1177 and eswyt 29) were evaluated under 15% polyethylene glycol (peg-6000) induced osmotic stress (3 bar). germination characteristics (germination rate, co-efficient of germination and germination vigor index), shoot and root length, shoot and root dry weight, and seed metabolic efficiency decreased under osmotic stress induced by peg than control treatment. but the degree of reduction was different for various wheat genotypes. genotype baw 1177 showed the highest performance in respect to germination and early seedling traits at both control and peg induced osmotic stress than other three genotypes. so, genotype baw 1177 can be considered as relatively drought tolerant genotype. introduction in bangladesh wheat is the second most important cereal crop after rice (barma et al., 2019) grown over an area of 0.33 million hectares with an annual production of about 1.03 million metric tons (bbs, 2020). though wheat is an important cereal crop in bangladesh but its average yield is low (3.09 t ha-1) (bbs, 2020) as compared to that of the advanced countries. at present, the domestic production of the country can only encounter around 20% of total wheat demand (usda, 2018). however, wheat productivity has been declined due to various abiotic stresses over the last two decades particularly drought stress (shao et al., 2008). rising temperature and changing in precipitation pattern leads to increasing incidence and intensity of drought events in the country like bangladesh (khan et al., 2019) where drought employs expressively adverse effects on wheat production in northern and central part of the country (abhinandan et al., 2018). drought stress is responsible for either inhibition or delayed seed germination or seedling establishment (balkan and gençtan, 2013). it has negative effects on the morphological, physiological, and biochemical attributes of the wheat crop (chachar et al., 2016) and it results in a significant reduction in overall production (bilal et al., 2015 and abid et al., 2018). seed germination is a prerequisite and important transition stage for crop plants from seeds to seedlings. the semi-arid regions of the world experience low moisture availability during seed germination of wheat crop (farooq et al., 2019). low moisture availability during seed germination and subsequent growth stages of wheat crop declines final production of wheat as seedling stage of crop plants is highly vulnerable to the water deficit stress (rauf et al., 2007). 20 pramanik et al. seed germination and seedling emergence and/or establishment are important criteria for testing the tolerance of wheat genotypes to various abiotic stresses, particularly, drought stress (hubbard et al., 2012, rauf et al., 2007). evaluation of seed germination under polyethylene glycol (peg-6000) induced drought stress is the most common screening method used to test the drought tolerance of different crop plants during seed germination and early seedling establishment (awan et al., 2021). the use of osmotic substances of high molecular weight such as peg is a common method to test the drought tolerance of crop plants during seed germination and seedling establishment (zarei et al., 2007). several investigations indicated that in vitro screening using peg is one of the reliable approaches to select drought-tolerant genotypes based on germination indices (kocheva and georgiev 2003, shahbazi 2012). therefore, the present study was carried out to test the drought tolerance of four wheat genotypes at early seedling stage through peg-induced osmotic stress. materials and methods experimental site and period the experiment was conducted at crop physiology and ecology laboratory, hajee mohammad danesh science and technology university, dinajpur, bangladesh during november, 2021. experimental design and treatments four wheat genotypes were evaluated under two growing conditions control and 15% peg induced drought stress following completely randomized design with three replications. peg solution was prepared by dissolving calculating amount of peg (151.5 g / 1000 ml) in tap water as described by michel (1983). normal tap water was used as control treatment. characteristics of the wheat genotypes: bari gom 28: high yielding variety, duration: 105-110 days, plant height: 95-100 cm, 1000grain weight: 35-40 g, grain yield: 3.5-5.4 t/ha, tolerant to terminal heat stress, resistant to leaf rust and ug99 race of stem rust, moderately tolerant to bipolaris leaf blight, moderately susceptible to wheat blast and fit to the rice-wheat cropping system bari gom 29: high yielding variety, duration: 102-108 days, plant height: 95-100 cm, 1000grain weight: 44-48 g, grain yield: 4.0-5.0 t/ha, tolerant to terminal heat stress, and moderately susceptible to wheat blast baw 1177: advanced line of bangladesh wheat and maize research institute (bwmri) eswyt 29: advanced line of bwmri. spring bread wheat adapted to mega-environment 1 i.e. the optimally irrigated, low rainfall areas with an average minimum temperature in the coolest quarter between 3 and 11°c. (me1): seed placement and data collection on germination and seedling traits twenty-five seeds of each genotype were placed on filter paper soaked by treatment solution and distilled water according to treatment in 11 cm diameter sterilized petri dish. the 10 ml treatment solution or distilled water was poured on the filter paper and afterwards the solution or distilled water was given according to the needs. seedlings were allowed to grow up to 7 days after placement of germination. germination was counted at 24-hours interval starting from 72h after of seed set and continued up to 7th day. a seed was considered germinated as plumule and radicle came out and was larger than 2 mm long. the rate of germination was calculated according to krishnasamy and seshu, (1990) and co-efficient of germination and vigor index polyethylene glycol mediated osmotic stress on germination, seedling traits of wheat 21 were calculated using the formulae (copeland, 1976). at 7th days after seed placement for germination, five seedlings from each petri dish were sampled for shoot and root length. then shoot, root and remaining seeds were dried separately at 70oc for 72h in an electric oven (modele28# 03-54639, binder, germany) and weight were recorded with an electrical balance (modeland ek300i). the mean length and dry weight were calculated for each treatment combination. calculation of amount of seed material respired (smr) and seed metabolic efficiency (sme) smr was calculated as: smr = sdw – (shw + rtw + rsw), where, sdw = seed dry weight before germination, shw = shoot dry weight, rtw = root dry weight and rsw = remaining seed dry weight. seed metabolic efficiency was calculated using the formula (rao and sinha, 1993). the relative performance regarding different germination and seedling traits was calculated as described by asana and william (1965) using the following formula relative performance (%) = (variable measured under stress condition ÷ variable measured under normal condition) × 100 calculation of drought tolerance/resistance indices the drought tolerance/resistance indices based on different traits were calculated using the following formulas: i) tolerance (tol) = yp-ys (rosielle and hamblin 1981); where yp and ys are the mean values of genotypes under non-stress and stress conditions, respectively; the genotypes with low values of this index are more stable in two different conditions. ii) drought tolerance index (dti) = ys ÷ yp (goudarzi and pakniyat 2008); the genotypes with high value of this index will be more tolerant to stress. iii) drought sensitivity index (dsi) = (yp -ys) ÷ yp (farshadfar and javadinia 2011); the genotypes with low value of this index will be more desirable. iv) mean productivity (mp) (ys yp) ÷ 2 (rosielle and hamblin 1981); the genotypes with high value of this index will be more desirable. statistical analyses of data the experimental data were analyzed by partitioning the total variance using stata program (small stata 12.0) and the means were compared by tukey’s test at 5% level of probability. results and discussion germination characteristics the interaction effect of growing conditions and wheat genotypes significantly influenced the germination rate and germination vigor index but insignificant in co-efficient of germination (table 1). all the genotypes showed higher germination rate at control (84.83 to 98.48%) as compared to peg induced osmotic stress condition (64.11 to 79.12%). under stress condition, baw 1177 attained the highest germination rate (79.12%), whereas eswyt 29 had the lowest germination rate (64.11%). in relative performance, bari gom 29 showed the highest performance (87.49%) while eswyt 29 had the lowest performance (70.33%) and rest two genotypes bari gom 28 and baw 1177 showed moderate performance (77.12 and 80.34%, respectively). 22 pramanik et al. co-efficient of germination was found higher at control with a range from 35.49% in bari gom 29 to 36.44% in baw 1177 as compared to peg induced osmotic stress condition with a range from 33.73% in bari gom 29 to 34.91% in baw 1177. considering relative performance highest performance was found in baw 1177 (95.80%), while bari gom 28 had the lowest performance (94.35%). at control condition, the highest germination vigor index was found in baw 1177 (33.83), whereas the lowest in bari gom 29 (30.71). the moderate germination vigor index (32.44) was found in both bari gom 28 and eswyt 29. under stress condition, again baw 1177 attained the highest germination vigor index (27.15), while eswyt 29 had the lowest (23.87) which was statistically similar with bari gom 28 (24.02) and bari gom 29 (23.94). in relative performance, genotype baw 1177 showed the highest performance (80.25%), whereas eswyt 29 the lowest performance (73.58%). table 1. effects of polyethylene glycol induced osmotic stress (-3 bar) on germination characteristics of wheat genotypes genotypes growing conditions germination rate co-efficient of germination germination vigor index % rp (%) rp (%) rp (%) bari gom 28 control 96.57a 77.12 36.10 94.35 32.44a 74.04 stress 74.47b 34.06 24.02d bari gom 29 control 84.83a 87.49 35.49 95.04 30.71b 77.96 stress 74.22b 33.73 23.94d baw 1177 control 98.48a 80.34 36.44 95.80 33.83a 80.25 stress 79.12b 34.91 27.15c eswyt 29 control 91.15a 70.33 36.19 95.50 32.44a 73.58 stress 64.11b 34.56 23.87d cv (%) 1.34 1.96 1.44 in a column, means followed by the same letter(s) did not differ significantly at p ≤ 5% level by tukey test. rp = relative performance. a decline in germination percentage under moisture stress has been reported in wheat by sharma et al. (2022). they observed that the germination rate was reduced with the increment of water deficit stress but the degree of reduction in rate of germination was not similar for all wheat genotypes. development at the germination stage have been adopted a suitable growth stage for testing the drought stress tolerance in wheat. it could be assumed that the presence of increased concentrations of osmotic potential during the growth of germination stage inhibits the developmental traits and survival of wheat. differential degree of sensitivity in germination characteristics to peg induced water stress among the wheat genotypes may be due to genetic variability of wheat to water stress condition. mahpara et al. (2022) bilgili et al. (2019) and rana et al. (2017) similarly detected significant differences in germination characteristics of wheat genotypes under peg induced water deficit stress. early seedling growth early seedling growth (shoot length, root length, shoot dry weight, and root dry weight) of 7 days old seedling was significantly influenced by the interaction effect of growing conditions and wheat genotypes (table 2 and fig. 1). the longest shoot length was found at control with a range from 3.44 cm in bari gom 28 to 3.82 cm in baw 1177 as compared to stress condition with a range from 1.36 cm in bari gom 29 to 2.72 cm in baw 1177. at control condition, the longest shoot length (3.82 cm) was found in baw 1177 followed by 3.79 cm in eswyt 29 and 3.52 cm in bari gom 29, whereas the shortest shoot length (3.44 cm) was polyethylene glycol mediated osmotic stress on germination, seedling traits of wheat 23 found in bari gom 28. under stress condition, baw 1177 produced the highest shoot length (2.72 cm) followed by bari gom 28 (2.19 cm), while bari gom 29 had the lowest shoot length (1.36 cm) which was statistically identical with eswyt 29 (1.37 cm). normal tap water peg solution fig. 1. seven days old seedlings of wheat genotype grown under normal tap water and peg solution. considering relative performance, baw 1177 performed highest (71.20%), whereas eswyt 29 performed lowest (36.14%) followed by bari gom 29 (38.63%). moderate performance (63.66%) was found in bari gom 28. at control condition, baw 1177 produced the longest root (7.28 cm) followed by bari gom 29 (7.06 cm) and eswyt 29 (7.21 cm), whereas bari gom 28 produced the shortest root (6.18 cm). table 2. effects of polyethylene glycol induced osmotic stress (-3 bar) on early seedling growth of 7 days old seedlings of wheat genotypes genotypes growing conditions shoot length root length shoot dry weight root dry weight cm rp (%) cm rp (%) mg rp (%) mg rp (%) bari gom 28 control 3.44a 63.66 6.18b 78.64 0.030bc 76.66 0.040b 70.00 stress 2.19b 4.86c 0.023d 0.028d bari gom 29 control 3.52a 38.63 7.06a 64.44 0.033ab 72.72 0.035c 71.42 stress 1.36c 4.55c 0.024d 0.025e baw 1177 control 3.82a 71.20 7.28a 82.14 0.035a 77.14 0.045a 73.33 stress 2.72b 5.98b 0.027cd 0.033c eswyt 29 control 3.79a 36.14 7.21a 64.07 0.031abc 58.06 0.038bc 52.63 stress 1.37c 4.62c 0.018e 0.020e cv (%) 6.61 6.16 6.14 2.99 in a column, means followed by the same letter(s) did not differ significantly at p ≤ 5% level by tukey test. rp = relative performance. under stress condition, baw 1177 produced the longest root (5.98 cm), whereas bari gom 29 had the shortest root (4.55 cm). but under stress condition, all the genotypes produced statistically similar root length. in relative performance, it was found that genotype baw 1177 showed higher relative root length (82.14%) compared to others genotypes (78.64% in bari gom 28, 64.44% in bari gom 29 and 64.07% in eswyt 29). results showed that shoot dry weight was decreased at water stress condition. minor variations among the wheat genotypes both under control (0.030 mg to 0.035 mg) and peg induced water deficit (0.018 mg to 0.027 mg) conditions were observed. under control condition, baw 1177 attained the highest shoot dry weight (0.035 mg) followed by bari gom 29 (0.033 mg) and eswyt 29 (0.031 mg), whereas bari gom 28 had the lowest shoot dry weight (0.03 mg). 24 pramanik et al. under water stress condition, eswyt 29 showed the lowest shoot dry weight (0.018 mg) and highest shoot dry weight was found in baw 1177 (0.027 mg) followed by bari gom 28 (0.023 mg) and bari gom 29 (0.024 mg). in relative performance, it was found that the genotype baw 1177 and bari gom 28 showed the higher relative value (77.14 and 76.66%), whereas eswyt 29 attained the lowest relative value (58.06%) in shoot dry weight. bari gom 29 showed moderate performance (72.72%) compared to others. results showed that root dry weight was decreased at stress condition. there existed minor variations among the wheat genotypes both at control (0.035 mg to 0.045 mg) and peg induced osmotic stress (0.024 mg to 0.033 mg) conditions. under control condition, baw 1177 showed the highest root dry weight (0.045 mg), whereas bari gom 29 had the lowest (0.035mg) and it was at par with eswyt 29 (0.038 mg). under osmotic stress condition, eswyt 29 showed the lowest root dry weight (0.024 mg) followed by bari gom 29 (0.025 mg) and highest root dry weight was found in baw 1177 (0.033 mg). in relative performance, genotype baw 1177 showed the higher relative value (73.33%) and eswyt 29 lower relative value (52.63%). moderate performance was found in bari gom 29 (71.42%) followed by bari gom 28 (70.00%). reduction in seedling growth is the result of restricted cell division and enlargement, as drought stress directly reduces growth by decreasing cell division and elongation (kramer, 1983). reduction in shoot and root length might be due to less water absorption and decrease in external osmotic potential created by peg (kaydan and yagmur, 2008). significant reduction in term of shoot length, root length and seedling dry weight among the genotypes might be attributed to their differential response in term of tolerance level to moisture stress. these results of the present study are parallel to the findings of faisal et al. (2019) mahpara et al. (2022) and sharma et al. (2022). seed metabolic efficiency (sme) the significant variation of sme of four wheat genotypes at different growing conditions is presented in table 3. at control condition, genotype baw 1177 attained the maximum sme (3.36 g g-1) which was statistically identical with eswyt 29 (2.91 g g-1), whereas lowest sme in bari gom 29 (1.41 g g-1) followed by bari gom 28 (1.47 g g-1). at peg induced osmotic stress, genotype baw 1177 attained the highest sme (2.4 g g-1), whereas eswyt 29 the lowest sme (0.65 g g-1) followed by bari gom 29 (0.72 g g-1) and bari gom 28 (0.96 g g-1). stress condition reduced the sme in all genotypes but the magnitude of reduction in sme was not similar in all genotypes. in relative performance, highest performance was performed by baw 1177 (71.43%) and lowest performance by eswyt 29 (22.33%). table 3. effects of polyethylene glycol induced osmotic stress (-3 bar) on seed metabolic efficiency of wheat genotypes genotypes growing conditions seed metabolic efficiency g g-1 relative performance (%) bari gom 28 control 1.47b 65.30 stress 0.96c bari gom 29 control 1.41b 51.06 stress 0.72c baw 1177 control 3.36a 71.43 stress 2.40a eswyt 29 control 2.91a 22.33 stress 0.65c cv (%) 6.15 in a column, means followed by the same letter(s) did not differ significantly at p ≤ 5% level by tukey test. polyethylene glycol mediated osmotic stress on germination, seedling traits of wheat 25 the reduction in sme at water stress condition suggested that at water stress, substrate respiration was not linked to building useful plant parts (shoot and root) and could lead to thermal dissipation of respiratory energy by an alternate oxidase pathway or cyanide resistant pathway. reduction in sme may be attributed to inability to accumulate respiratory product to wheat seedlings. the results are in accordance of findings of sikder et al. (2010). they concluded that seed metabolic efficiency of wheat genotypes was affected to a greater extent under stress condition. correlation analysis among different germination and early seedling traits correlation analysis among different germination and early seedling traits in this investigation presented in table 4 indicates that all the traits maintained a significant positive relation with each other. table 4. correlations (pearson) among the different germination and seedling traits of wheat genotypes germination rate co-efficient of germination germination vigor index shoot length root length shoot dry weight root dry weight seed metabolic efficiency germination rate 1.000** co-efficient of germination 0.926** 1.000** germination vigor index 0.889** 0.972** 1.000** shoot length 0.835** 0.902** 0.891** 1.000** root length 0.833** 0.868** 0.880** 0.923** 1.000** shoot dry weight 0.799** 0.780** 0.780** 0.872** 0.850** 1.000** root dry weight 0.9311** 0.9210** 0.8795** 0.9014** 0.8345** 0.8855** 1.0000** seed metabolic efficiency 0.768** 0.649** 0.556** 0.533* 0.561** 0.647** 0.756** 1.000** ** and * indicate significant at the 1% and 5% probability level, respectively. relationship of different seedling traits with seed metabolic efficiency different seedling attributes (shoot length, root length, shoot dry weight and root dry weight) of wheat genotypes maintained a positive linear relationship with seed metabolic efficiency (fig. 2). the results revealed that the genotype with higher sme produced higher shoot length, root length, shoot dry weight and root dry weight, while the genotype with lower sme provided lower values of that attributes. it indicated that the seedling traits of wheat genotypes increased with the increment of sme and decreased with the decreasing of sme. the higher shoot length, root length, shoot dry weight and root dry weight resulted from higher sme probably due to the genotype with higher sme links adequate substrate respiration to build useful plant parts (shoot and root). it also might be due to the more ability of genotype with higher sme to accumulate respiratory product to wheat seedlings. drought tolerance/resistance indices drought tolerance, drought tolerance index, drought sensitivity index and mean productivity of wheat genotypes based on different germination and early seedling traits are presented in table 5. variation in different indices observed in different wheat genotypes indicating different levels of drought tolerance under peg induced osmotic stress. the genotype with the least tol and dsi and the highest dti, and mp showed more tolerance to stress condition than the other 26 pramanik et al. genotypes. farshadfar et al. (2013) and hooshmandi (2019) used tol, dti, dsi and mp as a tolerance criterion for wheat genotypes in stress conditions. fig. 2. linear relationship of different seedling traits with seed metabolic efficiency. table 5. drought tolerance /resistance indices of wheat genotypes based on different germination and seedling traits wheat genotypes tolerance/resistance indices germination and seedling traits gr cg gvi sl rl sdw rdw sme bari gom 28 tol 22.10 2.04 8.42 1.25 1.32 0.007 0.012 0.51 dti 0.77 0.94 0.74 0.64 0.79 0.770 0.700 0.65 dsi 0.23 0.06 0.26 0.36 0.21 0.230 0.300 0.35 mp 85.52 35.08 28.23 2.82 5.52 0.027 0.034 1.22 bari gom 29 tol 10.61 1.76 6.77 2.16 2.51 0.009 0.010 0.69 dti 0.87 0.95 0.78 0.39 0.64 0.730 0.710 0.51 dsi 0.13 0.05 0.22 0.61 0.36 0.270 0.290 0.49 mp 79.53 34.61 27.33 2.44 5.81 0.029 0.030 1.07 baw 1177 tol 19.36 1.53 6.68 1.10 1.30 0.008 0.012 0.96 dti 0.80 0.96 0.80 0.71 0.82 0.770 0.730 0.71 dsi 0.20 0.04 0.20 0.29 0.18 0.230 0.270 0.29 mp 88.80 35.68 30.49 3.27 6.63 0.031 0.039 2.88 eswyt 29 tol 27.04 1.63 8.57 2.42 2.59 0.013 0.018 2.26 dti 0.70 0.95 0.74 0.36 0.64 0.580 0.530 0.22 dsi 0.30 0.05 0.26 0.64 0.36 0.420 0.470 0.78 mp 77.63 35.38 28.16 2.58 5.92 0.025 0.031 1.78 gr = germination rate, cg = co-efficient of germination, gvi = germination vigor index, sl = shoot length, rl = root length, sdw = shoot dry weight, rdw = root dry weight, sme = seed metabolic efficiency, tol =tolerance, dti = drought tolerance index, dsi = drought sensitivity index, mp = mean productivity polyethylene glycol mediated osmotic stress on germination, seedling traits of wheat 27 conclusion based on different germination and early seedling traits evaluated as well as drought tolerance indices, genotype baw 1177 was found comparatively drought tolerant, whereas eswyt 29 was found drought susceptible and bari gom 29 and bari gom 28 were found moderately drought tolerant. references abhinandan, k., l. skori, m. stanic, n. hickerson, m. jamshed, m.a. samuel. 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osmotic stress impacts on growth and biochemical aspects of wheat (triticum aestivum l.) j. crop sci. biotech. 22(3): 213223. usda. 2018. foreign agricultural service. bangladesh, grain and feed annual. 2018. retrieved from https ://gain.fas.usda.gov/. accessed on 31 jan 2019. zarei, l., e. farshadfar, r. haghparast, r. rajabi and m.m.s. badieh. 2007. evaluation of some indirect traits and indices to identify drought tolerance in bread wheat (triticum aestivum l.). asian j. plant sci. 6(8): 1204-1210. bangladesh agron. j. 2022, 25(2): 31-41 effect of defoliation on growth and yield of maize m.n. jahan, m.a. hasan and m.r. islam department of crop physiology and ecology, faculty of agriculture, hajee mohammad danesh science and technology university, dinajpur–5200, bangladesh corresponding e-mail: rabiulislam@hstu.ac.bd (received: 02 august 2022, accepted: 26 november 2022) keyword: defoliation, green fodder, light intensity, spad value, zea mays abstract the experiment was conducted to evaluate the effect of defoliation on grain and fodder yield of maize at the research field and laboratory of crop physiology and ecology department, hajee mohammad danesh science and technology university, dinajpur during the period of december 2018 to june 2019. the trial was carried out in a randomized completely block design with three replications. the experimental treatments were: t1– control (without leaf removal), t2– defoliating all leaves except ear and adjacent two leaves above the ear at 7 days after silking (das), t3–defoliating all leaves except ear and adjacent two leaves above the ear at 14das, t4–defoliating all leaves below the ear at 7 das, t5– defoliating all leaves below the ear at 14 das, t6– detopping except two leaves above the ear at 7 das and t7–detopping except two leaves above the ear at 14 das. light intensity was increased (66.9 to 81.05%) when only lower leaves (t5) or both upper and lower leaves (t2) were removed, but when only the upper leaves (t6) were removed it was not increased. spad value was increased (13.58 to 24.5%) but number of leaves and leaf area plant-1 were reduced (60.5 to 63.09% and 64.4%) due to defoliation. substantial amount of green fodder was obtained (0.776 kg m-2) due to defoliation of maize. grain yield of maize was reduced (5.56 to 21.83%) due to different defoliation treatments but the yield reduction was not significant when only lower (t4) or upper (t7) leaves were removed. introduction maize (zea mays l.) belongs to the family poaceae is the world’s most widely grown cereal and global production revealed 1398.3 million metric tons in 2018–2019 (usda, 2019), it is one of the most important crops in bangladesh, which can be well–fitted in the cropping systems (hashem et al., 1983). its demand is increasing day by day and becoming an important cereal crop for its high productivity and diversified use (food items for human, fodder for livestock, feeds for poultry, fuel and raw materials for industry) in bangladesh (islam and kaul, 1986). maize production in bangladesh was 3500 thousand metric ton in the year 2018–2019 (usda, 2019). maize can be conserved as silage, which is a nutritious green fodder for livestock. artificial defoliation provides lot of green fodder at the time of fodder scarcity; hence, defoliation in maize has great impact at broad spectrum for livestock production. location of individual leaves with respect to the ear and photosynthetic efficiency of a variety decides photosynthate translocation rate to the ear. it is estimated that the middle four leaves (2 above and 2 below the ear) approximately contributes 50 percent of the total dry matter accumulation in the ear (allison and watson, 1966). defoliation of maize hybrids at later developmental stages (e.g. v11, vt, r3 and r5) reduced grain yield (hicks et al., 1977). but, when defoliation of leaves occur after ear development; plant l have the advantage of some 32 jahan et al. photosynthetic activity of the leaves and therefore, produces more seeds than the leaves defoliated earlier. proper time and level of defoliation seems to be very important for controlling lodging and obtaining enough forage without reducing grain yield (usman et al., 2007). the information on proper timing and level of defoliation in maize leaves is scarce in bangladesh. therefore, the present study was conducted to know the impact of different levels of defoliation on growth and yield (grain and forage) of maize. materials and methods the experiment was set up at the research field (latitude, longitude and elevation were 25º39′ n, 88º41′ e and 37.58 m, respectively) of crop physiology and ecology department, hajee mohammad danesh science and technology university, dinajpur during december 2018 to june 2019. the unit plot size (2.4 m × 2.0 m) was used for the experiment. the research was conducted following randomized completely block design (rcbd) with three replications and seven treatments. the treatments were: t1 (control i.e. without leaf removal), t2 (defoliating all leaves except ear and adjacent two leaves above the ear at 7 das),t3 (defoliating all leaves except ear and adjacent two leaves above the ear at 14 das), t4 (defoliating all leaves below ear at 7 das), t5 (defoliating all leaves below ear at 14 das), t6 (detopping except two leaves above the ear at 7 das) and t7 (detopping except two leaves above the ear at 14 das). a fertilizer dose of 86.0, 26.0, 41.0, 19.0, 6.0, 1.0 and 0.5 kg ha-1 n, p, k, s, mg, zn and b was applied in the form of urea, triple super phosphate (tsp), muriate of potash (mop), gypsum, magnesium sulphate, zinc sulphate and boric acid (frg, 2018). all fertilizers were applied as basal dose together with 1/3 urea and after irrigations 2/3 urea was top dressed. seeds of hybrid maize pac 293, advanta-brac were sown on december 1, 2018 at a row spacing of 60 and plant spacing 20 cm. two seeds were placed in each hole and after emergence healthy one seedling was kept. maize cobs harvested manually at physiological maturity stage (husk has turned yellow and the seeds were hard enough), dehusked and dried separately under shade. shelling was done with single cob maize sheller and seeds were dried under shade till moisture content reached 12%. five maize plants from each plot were randomly selected for data collection. the parameters first cob height, leaf number plant-1, light intensity in crop canopy and spad (soil plant analyses development) values were collected at 21, 28 and 35 das. light intensity in crop canopy (lux) was recorded using light meter (model: lx–102, origin: china) at noon under bright sunshine and less wind conditions. the sensor of the instruments was placed on the ground level at away from the edges of four corners. spad value was recorded from tagged plants from each plot using self–calibrating minolta chlorophyll meter (model: spad– 505, minolta co. ltd., japan) using the middle portion of cob bearing leaves. leaf area (cm2) was calculated using the formula of kvet et al. (1971) as leaf area plant-1 = mean leaf area × 0.75 × leaf number; where, 0.75 is a factor. cob length, cob diameter, number of rows of grains cob–1, number of grains row-1, grain number cob-1, single cob weight, weight of hundred grains, and grain, stover and green fodder yield also evaluated. the data were analyzed using statistix 10 program and treatment means compared by tukey’s range test at p ≤ 5% level. results and discussion growth parameters, light intensity and spad values of maize growth attributes such as the first cob height (figure 1) of maize plants was not significantly influenced by different defoliation treatments at 21, 28 and 35 days after silking (das) but number of leaves (figure 2) and leaf area plant-1 (figure 3) varied significantly. the maximum number of leaves were obtained by t1 (10.84, 10.66 and 10.13, respectively) followed by t7, effect of defoliation on growth and yield of maize 33 t6, t5 and t4; whereas the lowest number of leaves (4.00) in t2 and t3 treatments. the maximum leaf area plant-1 (0.749 m2) was recorded in t1 which was followed by t7, t4, t5 and t6 treatments and the lowest (0.2667 m 2) in t2 which was statistically similar to t3 treatment. here, t1 = control (without leaf removal), t2 =defoliating all leaves except ear and adjacent two leaves above the ear at 7 das, t3 = defoliating all leaves except ear and adjacent two leaves above the ear at 14 das, t4 = defoliating all leaves below ear at 7 das, t5 = defoliating all leaves below ear at 14 das, t6 = detopping except two leaves above the ear at 7 das and t7 = detopping except two leaves above the ear at 14 das, treatment means compared by tukey’s range test at p ≤ 5% level. fig. 1. effect of defoliation on first cob height of plant at 21, 28 and 35 das in maize. here, t1 = control (without leaf removal), t2 =defoliating all leaves except ear and adjacent two leaves above the ear at 7 das, t3 = defoliating all leaves except ear and adjacent two leaves above the ear at 14 das, t4 = defoliating all leaves below ear at 7 das, t5 = defoliating all leaves below ear at 14 das, t6 = detopping except two leaves above the ear at 7 das and t7 = detopping except two leaves above the ear at 14 das. treatment means compared by tukey’s range test at p ≤ 5% level. fig. 2. effect of defoliation on number of leaf plant-1at 21, 28 and 35 das in maize. 80 82 84 86 88 90 92 94 96 98 100 21 das 28 das 35 das f ir st c o b h e ig h t (c m ) treatments t1 t2 t3 t4 t5 t6 t7 a a a c c c c c c b b b b b b b b b b b b 0 1 2 3 4 5 6 7 8 9 10 11 12 21 das 28 das 35 das n o . o f le a f treatments t1 t2 t3 t4 t5 t6 t7 34 jahan et al. here, t1 = control (without leaf removal), t2 =defoliating all leaves except ear and adjacent two leaves above the ear at 7 das, t3 = defoliating all leaves except ear and adjacent two leaves above the ear at 14 das, t4 = defoliating all leaves below ear at 7 das, t5 = defoliating all leaves below ear at 14 das, t6 = detopping except two leaves above the ear at 7 das and t7 = detopping except two leaves above the ear at 14 das. treatment means compared by tukey’s range test at p ≤ 5% level. fig. 3. effect of different levels of defoliation on leaf area plant-1 in maize. the light intensity in canopy (figure 4) and spad values of leaves (figure 5) at 21, 28 and 35 das were significantly influenced by different defoliation treatments of maize. the maximum light intensity in canopy (9.84 thousand lux) at 21 das was recorded in t2 which was followed by t5, t4 and t3 and the lowest light intensity in canopy (5.08 thousand lux) in t6 which was statistically identical to t7 and t1 treatment. similar pattern of light intensity in canopy also found at 28 and 35 das. the maximum spad value (55.86) at 21 das was found in t3 which was statistically at par to t6, t4, t2, t7 and t5 treatments. the lowest spad value (47.56) was recorded in t1 treatment. the maximum spad value (55.2) at 28 das was found in t7 which was statistically identical to those observed in t3, t5, t4 and t6 treatments. the lowest spad value (46.6) was recorded in t2followed by t1 treatment. the maize plant showed almost similar spad values at 35 das as like as 28 das. the significant differences in number of leaves at 21, 28 and 35 das was noticed and it might be due to the obligation of defoliation treatments after 7 and 14 das. these findings are quite similar to those of vasilas and seif (1985) in corn. they revealed significant differences in number of leaves, leaf area plant-1 and lai at 90 das and at harvest noticed among the levels of defoliation may be due to imposition of defoliation treatments after 65 das. removing of leaves either 3 or 4 had a greater impact on lai than removal of 1 and 2 leaves because of the difference in size of leaves; leaves nearest ear were larger than those further from the ear (keating and wafula 1992). effects of leaf removing on lai were different according to the intensity of defoliation and leaf position (barimavandi et al., 2010). the results of the present study revealed that when only lower leaves or both upper and lower leaves removed, the canopy density at lower portion was decreased and light intensity was increased but when only the upper leaves were removed light intensity in the canopy was not increased. heidari (2012) also reported that the upper leaves are more efficient in absorbing light than lower leaves. the variation in spad value due to application of leaf clipping and density was found more a d d c c c b 0 1 2 3 4 5 6 7 8 t1 t2 t3 t4 t5 t6 t7 l e a f a re a p e r p la n t (t h o u sa n d c m 2 ) treatment effect of defoliation on growth and yield of maize 35 conspicuously at later stage of crop growth rather than early stages. in general, the higher the level of leaf clipping, higher was the spad value at the later stage of crop growth except highest density of leaf clipping (d3c4). here, t1 = control (without leaf removal), t2 =defoliating all leaves except ear and adjacent two leaves above the ear at 7 das, t3 = defoliating all leaves except ear and adjacent two leaves above the ear at 14 das, t4 = defoliating all leaves below ear at 7 das, t5 = defoliating all leaves below ear at 14 das, t6 = detopping except two leaves above the ear at 7 das and t7 = detopping except two leaves above the ear at 14 das. treatment means compared by tukey’s range test at p ≤ 5% level. fig. 4. effect of defoliation on light intensity in canopy at 21, 28 and 35 das in maize. here, t1 = control (without leaf removal), t2 =defoliating all leaves except ear and adjacent two leaves above the ear at 7 das, t3 = defoliating all leaves except ear and adjacent two leaves above the ear at 14 das, t4 = defoliating all leaves below ear at 7 das, t5 = defoliating all leaves below ear at 14 das, t6 = detopping except two leaves above the ear at 7 das and t7 = detopping except two leaves above the ear at 14 das. treatment means compared by tukey’s range test at p ≤ 5% level. fig. 5. effect of defoliation on spad value at 21, 28 and 35 das in maize. d c d a a a c a c c b c b a b d e d d e c e 0 1 2 3 4 5 6 7 8 9 10 11 21 das 28 das 35 das l ig h t in te n si ty ( t h o u sa n d l u x ) treatment t1 t2 t3 t4 t5 t6 t7 b b c a b c a a a b a a b c a b a a b a a a b a b a a 30 35 40 45 50 55 60 65 70 21 das 28 das 35 das s p a d v a lu e treatments t1 t2 t3 t4 t5 t6 t7 36 jahan et al. regardless of density spad value in every treatment plants declined sharply from 14 das compared to clipping treatments. this might be due to the greater demand of cob development and its maturation along with scarcity of leaves (emran, 2010). yield contributing traits yield contributing traits such as cob length, number of grains row–1, and number of grains cob-1, single cob weight, grain weight cob-1, 100-grain weight were significantly influenced by different defoliation treatments but cob diameter and number of rows cob–1 insignificant (table 1). the maximum cob length (17.01 cm) was found in t7 which was followed by t6 and t5 and the lowest cob length (14.41 cm) in t2 which followed by t3. however, the cob length was reduced 8.39 percent in t2, 3.6 percent at 14 das (t3), while it was increased 5.72% in treatmentt4, 6.48% in t5, 6.99% at t6 and 8.13% in treatment t7. the percent reduction in number of grains row-1 were 19.78 in treatment t2, while 3.31, 4.72, 1.05, 2.62, t3, 3.31% reduction revealed in t4, t5, t6 and t7 treatments, respectively. the maximum number of grains cob -1 (573.25) was found in t1 which was statistically identical to t4, t5, t7 and t3 treatments and the lowest number of grains cob-1 (472.33) in t2. defoliating all leaves except ear and adjacent two leaves above the ear at 7 das (t2) reduced the number of grains cob -1 compared to other treatments. the highest single cob weight (185.8 g) was found in t1 which was statistically identical to t4, t7 and t5 treatments and the lowest single cob weight (130.5 g) in t2. however, the percent reduction in single cob weight were 29.76 percent in t2, 13.61 percent in t3, 5.16 percent in t4, 6.67 percent in t5, 10.22 percent in t6 and 5.22 percent in t7 treatments. the maximum grain weight cob-1(156.9 g) was recorded in t1 which was statistically similar to t4 and t7. the lowest grain weight cob -1 (112.6 g) was obtained from in t2 treatment. however, the percent reduction in grain weight cob-1 were 28.23 percent in t2, 12.81 percent in t3, 4.39 percent in t4, 6.30 percent in t5, 9.24 percent in t6 and 3.95 percent in t7 treatments. the maximum 100–grain weight (28.93 g) was found in t1 which was statistically identical to t4, t5, t7 and t6 treatments and the lowest 100–grain weight (25.86 g) in t2 treatments. however, the percent reduction in 100–grain weight, were 10.61 percent in t2, 4.59 percent in t3, 1.97 percent in t4, 0.95 percent in t5, 3.45 percent in t6 and 2.86 percent in t7 treatment. the intensities of defoliation and position of leaves on the plant and defoliation time are the most effective factors on the ear length (tilahun, 1993). emam et al. (2013) and souza et al. (2015) revealed the artificial defoliation in reproductive stages responsible for reduction of cob length. these outputs support the present findings. leaf situated one or two above the ear is the principle source of assimilates for the cob development. reductions of the ear diameter in maize at vegetative and reproductive stages due to defoliation were observed by souza et al. (2015), this result is in parallel with the present findings. this result are in accordance with the findings of barimavandi et al. (2010), heidari (2013) and jalilian and delkhoshi (2014) who reported that removing of above leaves of ear could decrease the number of grains in row. kabiri (1996) and echarte et al. (2006) stated that leaf removal at 50% silking resulted in the loss of grain number and so, less stem reserves were exploited because of the deficiency of physiological sinks. these outputs support the findings of present investigation. according to alvim et al. (2011), photosynthetically active leaf area loss above the ear affects the cob mass of maize due to defoliation. zewdu and asregid (2001) also reported that cob weight was reduced under defoliation. heidari (2012) who noted that cob weight was decreased with increasing defoliation intensity. presence of two above leaves is important to form ear with thick and big skin. this skin photosynthesis and reserves had a remarkable effect on row number, length and weight of cob. these findings are in agreements with the present outputs. it seems that seed weight is more dependent on genetic factors than environmental factors (heidari et al., 2009). however, effect of defoliation on growth and yield of maize 37 it was reported that in maize no defoliation produced the maximum seed weight cob-1 and minimum seed weight cob-1 was obtained in defoliation of all leaves below cob at two weeks after mid silking stage (chaudhary et al., 2005). the reason for decreasing grain weight cob-1 in d1 might be due to lower dry matter accumulation and less translocation of assimilates to grains as affected by early stages of detopping (maposse and nhampalele, 2009). assimilate availability can effect mean grain weight at early grain development stages, so that increasing availability of assimilate at later stages of grain filling would not affect mean grain weight (lauer et al. 2004). table 1. influence of different levels of defoliation on yield contributing traits of maize at different days after silking treatments cob length cob diameter number of rows cob–1 number of grains row–1 cm % change over control cm % change over control no. % change over control no. % change over control t1 15.73 d – 15.52 – 15.06 – 38.06 a – t2 14.41 f –8.39 14.54 –6.31 15.46 +2.65 30.53 b –19.78 t3 15.15 e –3.60 15.17 –2.25 14.80 –1.72 36.80 a –3.31 t4 16.60 c +5.72 15.37 –0.96 15.46 +2.65 36.26 a –4.72 t5 16.75 bc +6.48 15.14 –2.44 14.80 –1.72 37.66 a –1.05 t6 16.83 b +6.99 15.01 –3.28 14.13 –6.17 37.06 a –2.62 t7 17.01 a +8.13 15.31 –1.35 14.80 –1.72 36.80 a –3.31 cv (%) 4.35 3.29 3.11 1.42 table 1 continued treatments number of grains cob-1 single cob weight grain weight cob-1 100 -grain weight no. % change over control g % change over control g % change over control g % change over control t1 573.25 a – 185.8 a – 156.9 a – 28.93 a – t2 472.33 c –17.60 130.5 d –29.76 112.6 d –28.23 25.86 c –10.61 t3 544.77 ab –4.96 160.5 c –13.61 136.8 cd –12.81 27.60 b –4.59 t4 560.93 ab –2.14 176.2 ab –5.16 150.0 ab –4.39 28.36 ab –1.97 t5 557.38 ab –2.76 173.4 ab –6.67 147.0 b –6.30 28.66 ab –0.95 t6 524.00 b –8.59 166.8 bc –10.22 142.4 c –9.24 27.93 ab –3.45 t7 545.58 ab –4.82 176.1 ab –5.22 150.7ab –3.95 28.10 ab –2.86 cv (%) 3.70 4.05 13.07 2.21% here, t1 = control (without leaf removal), t2 =defoliating all leaves except ear and adjacent two leaves above the ear at 7 das, t3 = defoliating all leaves except ear and adjacent two leaves above the ear at 14 das, t4 = defoliating all leaves below ear at 7 das, t5 = defoliating all leaves below ear at 14 das, t6 = detopping except two leaves above the ear at 7 das and t7 = detopping except two leaves above the ear at 14 das, treatment means compared by tukey’s range test at p ≤ 5% level. defoliating all leaves except ear and adjacent two leaves above the ear at 7 das (t2) reduced the 100–grain weight compared to other treatments (table 1). these results are in accordance with the findings of emam et al. (2013) who reported that maximum 1000–grain weight (220 g) was obtained from control as well as 50% defoliation at 30 days after mid–silking and minimum (90 g) was obtained from 100% defoliation at mid–silking. jalilian and delkhoshi (2014) observed the effect of leaf clipping treatments on the 1000 -grain weight was significant. 38 jahan et al. grain, fodder and stover yields of maize table 2 reveals that different yields of maize such as grain, green fodder and stover yields were significantly influenced due to various defoliation treatments. the maximum grain yield (1193 g m-2) was found in t5 which was statistically identical to t7 and t1 treatments and the lowest grain yield (913 g m-2) in t2 treatments. however, the percent reduction in grain yield were 21.83 percent in t2 treatment , 11.81 percent in t3, 5.56 percent in (t4) and 6.25 percent in treatment t6 and the percent increase in grain yield were 2.14 percent in t5, and 0.06 percent when detopping done except two leaves above the ear at 14 das (t7). table 2. influence of different levels of defoliation on yields of maize at different days after silking treatments grain yield green fodder yield stover yield plant-1 g m-2 % change over control g m-2 g % change over control t1 1160 ab – 0.00 f 209.40 a – t2 910 d –21.83 776.06 a 151.40 c –27.69 t3 1030 c –11.81 758.40 a 162.90 bc –22.20 t4 1100 bc –5.56 706.50 b 196.40 ab –6.20 t5 1193 a +2.14 587.10 c 171.80 bc –17.95 t6 1090 bc –6.25 489.10 e 192.60 ab –8.02 t7 1170 ab +0.06 547.80d 220.40 a +5.25 cv (%) 4.39 2.26 9.93 t1 = control (without leaf removal), t2 =defoliating all leaves except ear and adjacent two leaves above the ear at 7 das, t3 = defoliating all leaves except ear and adjacent two leaves above the ear at 14 das, t4 = defoliating all leaves below ear at 7 das, t5 = defoliating all leaves below ear at 14 das, t6 = detopping except two leaves above the ear at 7 das and t7 = detopping except two leaves above the ear at 14 das, treatment means compared by tukey’s range test at p ≤ 5% level. defoliating all leaves except ear and adjacent two leaves above the ear at 7 das (t2) reduced the grain yield compared to other treatments. the maximum green fodder yield (776.06 g m-2) was found in t2 which was statistically identical to t3 and the lowest green fodder yield (0.00 g m-2) was found in t1 which was followed by t7 and t6. the maximum stover yield plant -1 (220.4 g) was found in t7 which was statistically identical to t1, t4 and t6 treatments and the lowest stover yield plant-1 (151.4 g) in t2 which was at par to t5 and t3 treatments. however, the percent reduction in stover yield plant-1 were 27.69 percent in t2, 22.20 percent in t3, 6.20 percent in t4, 17.95 percent in t5, 8.02 percent in t6 and the percent reduction in stover yield plant-1 was 5.25 percent in t7. grain yield is the product of number of plant m-2, cobs plant-1, grains cob-1 and individual grain weight. a change in any of these characters due to defoliation ultimately affects the grain yield. hassen (2003) reported that the seed yield and stover yield of maize were significantly influenced by the rate of various defoliation levels (0, 25, 50, 75 and 100%). however, adee et al. (2005) calculated that the upper 8 to 10 leaves contributed 88% of the grain yield. grain yield losses associated with defoliations around tasseling/silking are mainly explained by fewer kernel number (kn) (severini et al., 2011), while losses for defoliations right before or at grain filling period (r2, blister stage and on) are largely related to decline in kernel weight (echarte et al., 2006; abendroth et al., 2011). reduction in yield with defoliation treatment in maize was reported by gaias et al. (2017), battaglia (2014), heidari (2017) and alvim et al. (2011). defoliation of all leaves above ear (l3) recorded lesser dry matter production compared to other effect of defoliation on growth and yield of maize 39 levels of defoliation which may be due to heavy loss of foliage’s and photosynthetically active leaf area and their inability to intercept the light which resulted in inadequate synthesis of food reserves. hassen (2003) reported that the grain yield and stover yield of maize were significantly influenced by the rate of defoliation (0, 25, 50, 75 and 100%) treatments. conclusion from the overall results it was concluded that light intensity in the crop canopy was increased when only lower leaves or both upper and lower leaves were removed, but when only the upper leaves were removed light intensity in the canopy was not increased. spad value which indicated the greenness of leaf was increased due to defoliation. grain yield of maize was reduced due to different defoliation treatments but the yield reduction was not significant when only lower or upper leaves were removed and it was significant when both upper and lower leaves were removed. so, farmers could harvest green fodder either from lower or upper leaves to ear without significant yield reduction of maize. references abendroth, l.j., r.w. elmore, m.j. boyer and s.k. marlay. 2011. corn growth and development, pmr 1009. iowa state university extension, ames, iowa. adee, e.a., l.e. paul, e.d. nafziger and g. bollero. 2005. yield loss of corn hybrids to incremental defoliation. crop manag. 4(1), doi:10.1094/cm-2005-0427-01-rs. allison, j.c.s. and d.j. watson. 1966. the production and distribution of dry matter in maize after flowering. ann. bot. 30: 365–38. alvim, k.r.t., c.h. brito, a.m. brandão, l.s. gomes and m.t.g. lopes. 2011. redução da área foliar em plantas de milho na fase reprodutiva. revista ceres. 58: 413–418. barimavandi, a.r., s. sedaghathoor and r. ansari. 2010. effect of different defoliation treatments on yield and yield components in maize (zea mays l.) cultivar of s.c704. aust. j. crop sci. 4(1): 9–15. battaglia, m.l. 2014. corn (zea mays l.) yield response to defoliation at different row widths. an m. sc. 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(ag) thesis. department of seed science and technology, dharwad university of agricultural sciences, dharwad – 580005. usda, 2019. united states department of agriculture (usda).world agricultural production, foreign agricultural service. p.14. usman, k., e.j. khan, q. khan, a. wakil and m.u. khan. 2007. effect of detopping on forage and grain yield of rice under agro–climatic conditions of d.i. khan. sarhad j. agric. 23(1): 1–4. vasilas, b.l. and r.d. seif. 1985. defoliation effects on two corn inbreds and their single–cross hybrid. agron. j. 77: 816–820. zewdu, t. and d. asregid. 2001. effect of growing annual forage legumes with maize and maize leaf defoliation on grain and stover yield components and under sown forage production. in: 7th eastern and southern africa regional maize conference, nairobi. pp. 487–490. bangladesh agron. j. 2022, 25(2): 73-82 foliar application effects of zinc oxide nanoparticles on growth, yield and drought tolerance of soybean d.b. dola and m.a. mannan department of agronomy, bangabandhu sheikh mujibur rahman agricultural university gazipur-1706, bangladesh corresponding e-mail: mannanagr@bsmrau.edu.bd (received: 16 november 2022, accepted: 29 december 2022) keywords: soybean, nano fertilizer, drought mitigation abstract in modern agriculture, the application of nano fertilizers is increasing the productivity and stability of different crops by reducing the destructive effects of abiotic stresses. the nano particles are significant for their particle shape, potential reactivity, tunable pore size and high surface area. a pot experiment was conducted at the department of agronomy, bangabandhu sheikh mujibur rahman agricultural university, gazipur during rabi season (december 2020 to march 2021) to evaluate the effects of foliar spray of nano zinc (zno) in varying doses (0, 100 and 200 ppm) on growth, dry matter accumulation and yield of soybean under drought (40% of field capacity, fc) and control (80% of fc) conditions. the trial was conducted in a completely randomized design (crd) with three replications. plant height; fresh and dry weight of leaf, stem and whole plant; number of pods per plant; number of seeds pod-1; 100-seed weight and seed yield of soybean were suppressed due to drought stress. under both drought and control conditions, the foliar application of nano zinc substantially improved the growth, dry matter accumulation and yield of soybean. in drought condition, the foliar spray of 200 ppm nano zinc solution increased plant height, total fresh and dry weight by 21.69, 34.23 and 76.03%, respectively. in drought conditions, nano zn particles at 100 and 200 ppm increased seed yield by 26.79 and 63.50%, and in control conditions by 13.07 and 23.56%, respectively. as such the results indicated that foliar application of nano zinc oxide improved growth, yield and drought tolerance of soybean. introduction soybean (glycine max) is an annual self-pollinated diploid legume under the family fabaceae. soybean is recognized as an oil seed containing several useful nutrients including protein, carbohydrate, vitamins, and minerals. according to index mundi (2021), the soybean production in 2020 was 156,000 mt and also it has been increased about 44% for last decade in bangladesh. the annual soybean production and imports are increasing gradually to meet the feed requirements for the livestock, poultry and fisheries sectors, and soybean oil for human consumption (usda, 2019). among the abiotic factors, the drought is considered the most devastating, affecting all plants growth and development stages causing huge losses in soybean yield (engels et al., 2017). drought stress is a multidimensional stress and causes changes in the physiological, morphological, biochemical, and molecular traits in plants which ultimately affects negatively on mailto:mannanagr@bsmrau.edu.bd 74 dola et al. yield of plants (salehi-lisar and bakhshayeshan-agdam, 2016). since drought tolerance is a quantitative trait and many genes are involved, it is difficult to create a molecular marker for a plant’s response to a water deficit (sinclair, 2011). furthermore, the timing, intensity, and duration of a drought varies (mir et al., 2012), creating a hurdle for properly testing varieties. therefore, plant breeders typically combine data from multi-location trials to test new varieties, determine how genotypes respond across environments, and minimize effects of genotype by environment interactions (crossa, 1990). the use of nano fertilizers has led to the increased productivity, stability due to reduction of biotic and abiotic stresses as well as reduced production costs in the last decade (kashyap et al., 2016, 2017). according to davar et al. (2014), different trace elements and their oxides of nano particles were used for enhancing drought stress resistance in different plants. additionally, sharifi and khoramdel (2016) was found that foliar application of zn nano particles combined with the inoculum of bradyrhizobium japonicum improved yield of soybean. sheykhbaglou et al. (2010) observed that foliar application of nano-iron oxide at the concentration of 750 ppm increased leaf and pod dry weight over the control. nano particles are characterized by its particle shape, tunable pore size, potential reactivity and high surface area (seleiman et al., 2021). in plants, the cellular organelles are targeted, and certain contents are released through the nano particle target (cunningham et al., 2018). in agriculture, a wide scope of nano technology is still unexplored. above circumstances, the present research was conducted to study the effect of the foliar application of nano zno fertilizer on growth, dry matter accumulation and yield of soybean plant under drought condition. materials and methods location the pot experiment was conducted under semi-controlled environment in poly house condition in the department of agronomy, bangabandhu sheikh mujibur rahman agricultural university (bsmrau), bangladesh during 2020-2021. the experimental site was situated in a subtropical climatic zone of madhupur tract (aez 28) (24.09° n latitude and 90.26° e longitude) above 8.4 m above the mean sea level and about 40 km north of dhaka. plastic pots (30 cm length and 24 cm diameter) were used in the experiment which was filled with soil, holds about 28% moisture at field capacity (fc). soil used in the plastic pots was clay loam with 40.51% sand, 28.78% silt and 30.71% clay having ph of 6.93. the soil organic carbon, available p, exchangeable k were 0.61%, 0.8 mg 100g-1 soil and 0.79 cmolc kg -1 dry soil, respectively. the soil was mixed with cowdung at 1:0.25 ratio and dried well. then each pot was filled with 11 kg of that soil mixture. plant materials and preparation of nano solution soybean variety bu soybean-1 was used in this experiment. this high yielding variety was released by the bangabandhu sheikh mujibur rahman agricultural university. for the preparation of nano zinc solution, zinc nano powder of having 50-100 nm particle size and 1525 m2/g have been used and zinc was 79.1-81.5% (complexometric titration) (sigma-aldrich, 2016). to prepare 100 ppm nano zno solution, 100 mg of this powder was added to 1 l of distilled water and similarly, 200 ppm nano zno solution was prepared by adding 200 mg of that zno powder into 1 l of distilled water. both of the solutions were heated at 60°c temperature for 16 hours on magnetic stirrer with hot plate. after that, sonication bath was given to both solutions with vibration to mix all the particles into the water homogenously, so that the solution can foliar application of nanoparticles on growth, yield and drought tolerance of soybean 75 penetrate through the plant leaves effortlessly during the application (sandhya et al., 2021). then those solutions were stored in a plastic bottle at room temperature. the required amount of solution was inserted into the hand sprayer during the application of the solution into the plant. treatments and intercultural operation ten healthy seeds were sown maintaining uniform spacing in each pot. after sowing, minimal irrigation was applied by using a beaker to maintain uniform germination. thinning was done during the appearance of first two leaf stage and kept three uniform and apparently healthy plants in each pot. uniform application of 0.32 g urea, 0.933 g tsp and 0.64 g mop was given into each pot corresponding to 80-205-128 kg urea, triple super phosphate and muriate of potash ha-1, respectively (frg, 2018). after trifoliate stage the pots were investigated regularly to identify the moisture level of soil by using portable digital moisture meter (pogo soil sensor ii, stevens, usa) and 1 l of water was added on a regular basis to maintain the field capacity to 80% in nine pots of well-watered (control) plants and 500 ml was added to the rest of the each pot which were kept in water stressed condition by having 40% field capacity (drought) throughout the growing season. the experiment consisted of two factors. factor a: i. well water (control), ii. drought, factor b: 3 doses of nano zno. the control and drought treated plants leaves were sprayed with water (0 ppm nano zno), 100 ppm nano zno solution and 200 ppm nano zno solutions through a hand sprayer after 15 days beginning of drought stress. the experiment was laid out in completely randomized design (crd) with three replications. growth and yield parameters morphological growth related parameters, such as height of plants, leaf, stem fresh weight and total dry weight were observed after 15 days of spraying (at flowering stage). at the physiological maturity stage, seed yield plant-1, number of pods plant-1, number of seed pod-1, and 100-seed weight were also recorded. statistical analysis the crop stat statistical software version 7.2 has been used to analyze the recorded data. mean values of all treatments were compared using least significance difference (lsd) test at 5% level of significance results and discussion plant height plant height is one of the most important morphological traits to determine the growth and development of the plant. the scarcity of water affected the increment of plant height remarkably (figure 1). the height of soybean plants had been decreased by 15.85% under drought relative to the control condition. in control condition, plant height had reached maximum to 32.07 cm after the application of 200 ppm of nano zno fertilizer and the lowest was 26.95 cm in untreated plants. in drought condition the highest height was found into the plants which were treated with 200 ppm nano fertilizer. among all of the treatments, the untreated plants remained to the rock-bottom level with only 22.68 cm height under drought. more specifically, at 15 days after the application of 100 and 200 ppm of nano zno fertilizers, the height of the bu soybean-1 had been increased by 17.17 and 18.1%, respectively in control condition compared to the untreated plants. simultaneously, in drought condition, plant height had been increased significantly by 12.87 and 76 dola et al. 21.7%, due to the application of 100 and 200 ppm of nano zno fertilizers, respectively. similar result was reported by gholinezhad (2017), that application of nano fertilizer increased plant height by 20% in comparing to the control (no fertilizer) condition. according to dola et al. (2022), application of 200 ppm nano iron fertilizer enhanced the plant height by 21.24% in drought condition compared to the untreated plants. due to having small and high solubility compound, nano fertilizer absorbed quickly by plants and solved food shortages plants and increased plant growth (rasht, 2013). according to linh et al. (2020), height of nano particle treated plants reached approximately 50 cm, while 40 cm in the untreated control plants under drought conditions. fig. 1. effect of zinc fertilizer on plant height of soybean after 15 days of spraying. bars indicate (±se). znn0, znn1, znn2 = 0, 100 and 200 ppm nano fertilizer, respectively. fresh weight drought is one of the most alarming abiotic stress for soybean plants which affects almost all of the morphological traits of the plants severely. the water stressed condition affects fresh weight of leaf, stem and finally the total fresh weight of soybean plants adversely. due to drought condition, fresh weight of soybean leaves had been attenuated drastically by 28.36% compared to the control condition (table 1). but after the application of nano fertilizers, the amount of loss had been minimized. in control condition, the maximum leaf fresh weight was recorded 14.28 g after 200 ppm nano zinc solution spray, whereas, 11.32 g was the lowest. considering the water deficit condition, maximum fresh weight of leaves was 9.92 g found into 200 ppm nano zinc solution treated plants. among all of the experimental plants, untreated drought stressed plants were bearing the lowest sized leaves which were only 8.11 g. in drought stressed condition, fresh weight of soybean leaves increased by 13.07 and 22.32% at 15 days later of the foliar application of 100 and 200 ppm nano zno solution, respectively relative to untreated plants. in control condition, 100 and 200 ppm nano zinc fertilizers incremented the leaf fresh weight by 19.43 and 26.15%, respectively compared to the untreated plants. stem weight is also an impactful parameter which influences the total weight of a plant. the drought condition in vegetative stage of soybean plants deteriorated the fresh weight of stem by 37.24% compared to the control condition (table 1). the highest stem fresh weight of soybean was encountered as 6.08 g into the plants treated with 200 ppm nano zinc fertilizer and the minimum of 4.35 g into the untreated plants in control condition. in drought condition, the maximum fresh weight of soybean stem was 4.63 g achieved by the application of 200 ppm nano fertilizer and the lowest bc d a c a b 0 5 10 15 20 25 30 35 control (80% of fc) drought (40% of fc) p la n t h e ig h t (c m .) water regimes znn0 znn1 znn2 foliar application of nanoparticles on growth, yield and drought tolerance of soybean 77 stem fresh weight only 2.73 g into the untreated plants. in control condition, stem fresh weight improved by 17.47 and 39.77% at 15 days after 100 and 200 ppm nano zno fertilizers treatments application, respectively related to untreated plants. moreover, in drought condition, 100 and 200 ppm nano zinc solution accelerate the fresh weight of soybean plants exponentially by 28.94 and 69.6%, respectively compared to the plants remained untreated. evaluating all of the data mentioned above, it could be manifested that the solution of nano zinc particles also had a great impact on the total fresh weight of soybean plants. certainly, the water deficit condition into the soybean plants curtailed the total fresh weight by 30.82% compared to the plants grown in control condition (table 1). in control condition, the highest total fresh weight of soybean was found 20.36 g after the exogenous use of 200 ppm nano zno fertilizer and the minimum value was 15.67 g observed in totally untreated plants. in drought condition, the untreated plants had the lowest total fresh weight of 10.84 g only. but 15 days after the application of 200 ppm nano zinc particles in drought condition increased the total fresh weight of soybean to 14.55 g. in control condition, 100 and 200 ppm solution of nano zno improved the total fresh weight of soybean plants by 18.89 and 29.93%, respectively compared to the untreated plants. furthermore, the acceleration of the total fresh weight of soybean plants was 17.01 and 34.23% with the foliar application of 100 ppm and 200 ppm nano zinc fertilizer, respectively in drought condition relative to the untreated plants. this phenomenon should be considered as a noticeable increment in morphological growth of soybean plants. similar result was reported in green gram (vigna radiata l.) by raju et al. (2016). according to gülser et al. (2019), the highest stem fresh weight was found after the application of 30 mg kg-1 iron. linh et al. (2020) also found that treatment of nano particles improved the shoot development in both well-watered and drought-stressed plants at the vegetative stage. liu and lal (2014) have also claimed the similar result that using nano solutions increased the growth rate of soybeans by 33%. according to askary et al. (2017), the application of fe2o3 nanoparticles had significantly increased plant growth than the untreated plants. table 1. effect of zinc nano fertilizer on leaf fresh weight, stem fresh weight and total fresh weight of soybean after 15 days of spraying nano zinc (ppm) leaf fresh weight (g plant-1) stem fresh weight (g plant-1) total fresh weight (g plant-1) control drought control drought control drought 0 11.32b 8.11c 4.35ab 2.73b 15.67b 10.84c 100 13.52ab 9.17bc 5.11ab 3.52b 18.63ab 12.69bc 200 14.28a 9.92bc 6.08a 4.63ab 20.36a 14.55b lsd(0.05) 1.72 2.28 1.81 cv (%) 11.6 23.2 11.5 means followed by diverse letters differ significantly by lsd at p < 0.05 dry weight the harmful effect of water stressed condition in soybean plants declined the dry weight of different plant parts in vegetative stage remarkably. due to the drought condition, dry weight of soybean leaves had been decreased by 55.37% in vegetative stage of plants compared to the control condition (table 2). at 15 days after the foliar application of 200 ppm nano zinc fertilizer in control condition, the highest dry weight of soybean leaves was estimated as 2.48 g, whereas in this similar condition and stage, the untreated plants provided only 1.77 g dry weight of leaves in soybean plants. in drought condition, maximum 1.47 g of leaf dry weight was observed due to the foliar application of 200 ppm nano zinc solution. evidently, among all of 78 dola et al. the treatments and conditions, the lowest leaf dry weight (0.79 g) was found into the untreated drought affected plants. after the application of 100 and 200 ppm nano zno solution in control condition, dry weight of soybean leaves increased by 18.64 and 40.11%, respectively compared to the untreated plants. in drought condition, a significant increment of leaf dry weight by 37.97 and 86.08%, had been observed after the application of 100 and 200 ppm solution of nano zinc particles, respectively relative to the untreated plants. stem dry weight of soybean plants at vegetative stage had been deteriorated by 70.83% due to the hazardous effect of drought condition compared to the control condition (table 2). the highest amount of stem dry weight of soybean was 2.12 g, achieved by the foliar application of 200 ppm nano zinc solution in control condition. but due to avoiding all of the doses of nano zinc solution, stem dry weight of soybean plants was measured as only 1.44 g in control condition. conversely, the lowest stem dry weight of soybean plants was only 0.42 g found into the untreated plants grown in drought condition. in vegetative stage of soybean plants, 100 and 200 ppm nano zinc solution enhanced stem dry weight by 29.86 and 45.83%, respectively in control condition relative to the untreated plants. in drought condition, application of 100 and 200 ppm of nano zno fertilizer incremented stem dry weight by 35.71 and 59.52%, respectively compared to the untreated plants. table 2. effect of zinc nano fertilizer on leaf dry weight, stem dry weight and total dry weight of soybean after 15 days of spraying nano zinc (ppm) leaf dry weight (g plant-1) stem dry weight (g plant-1) total dry weight (g plant-1) control drought control drought control drought 0 1.77b 0.79c 1.44b 0.42c 3.22c 1.21f 100 2.1ab 1.1c 1.87a 0.57c 3.97b 1.66e 200 2.48a 1.47bc 2.12a 0.67c 4.60a 2.13d lsd(0.05) 0.41 0.27 0.40 cv (%) 14.1 13.0 8.1 means followed by diverse letters differ significantly by lsd at p < 0.05. after the analysis of the above mentioned data, it was evident that the nano zinc particles could outperform to improve the dry weight of soybean plants in vegetative stage. due to the harmful effect of drought, the total dry weight of soybean plants had dropped down by 62.42% relative to the control condition (table 2). the maximum total dry weight of soybean had been observed as 4.60 g into the plants treated with 200 ppm nano zno fertilizer in control condition. in control condition, only 3.22 g of total dry weight had been also noticed into the untreated plants. in drought condition, the highest amount of total dry weight of soybean plants was 2.13 g, attained after the application of 200 ppm nano zinc whereas, the lowest amount was only 1.21 g, obtained from the untreated plants suffering from drought condition. after the foliar application of 100 and 200 ppm of nano zno fertilizer in control condition, the total dry weight of soybean plants increased by 23.29 and 42.86%, respectively compared to untreated plants. in drought condition, the total dry weight had been accelerated sharply by 37.19 and 76.03% with the application of 100 and 200 ppm of nano zno fertilizer, respectively. chakralhoseini et al. (2002) found that iron at low concentration of 2.5 mg kg-1 in soil increased dry matter weight of soybean. sheykhbaglou et al. (2010) reported that application of nano-iron oxide at the concentration of 750 ppm caused an increase in dry pod weight and dry weight of leaf plus pod in soybean. according to vaghar et al. (2020), in early grain filling stage, the combined fe and zn foliar application increased the total dry matter content by 20.9%. foliar application of nanoparticles on growth, yield and drought tolerance of soybean 79 yield and yield contributing characters the number of pods is considered as one of most important yield components of soybean plants. due to the drought condition, the number of pods of soybean plants decreased by 25.36% compared to the control condition (table 3). the highest number of pods plant-1 was 61.86 found into 200 ppm nano zno fertilizer treated plants in control condition. in control condition, 54.11 pods plant-1 on average also found due to the lack of nano iron solution. the lowest number of pods were counted as 40.39 pods plant-1 into drought condition when none of the treatments were applied. in drought condition, about 52.94 pods plant-1 was also found after the application of 200 ppm of nano zno fertilizer. this foliar application of 100 and 200 ppm nano zno fertilizer in control condition increased the number of pods plant -1 by 8.43 and 14.32%, respectively in relation to the untreated plants. in drought condition, the application of 100 and 200 ppm nano zno fertilizer raised the average number of pods plant -1 by 47.78 and 52.94%, respectively compared to the untreated plants. the number of seeds pod-1 is directly related with the final yield content of soybean plants. about 27.62% less number of seeds pod-1 was found into a drought affected soybean plants compared to the control condition (table 3). the highest average number of seeds pod-1 (2.66) was recorded into 200 ppm nano zno fertilizer treated plants in control condition. in control condition, an average number of seeds pod-1 (2.10) when the plants remained untreated. the lowest number of seeds pod-1 was only 1.82 encountered into the untreated plants in drought condition. the foliar application of 200 ppm of nano iron solution increased seeds pod-1 to 1.86 seeds in drought condition. the application of 100 and 200 nano zno fertilizer increased the number of seeds pod-1 by 17.62 and 26.66%, respectively compared to the untreated plant. also in drought condition, the application of 100 and 200 ppm nano zno fertilizer improved the average number of seeds pod-1 in soybean plants by 13.16 and 19.74%, respectively relative to the untreated plants. table 3. effect of zinc nano fertilizer on number of pods plant-1, number of seeds pod-1, 100 seeds weight and seed yield of soybean nano zinc (ppm) number of pods plant-1 number of seeds pod-1 100seeds weight (g) seed yield (g plant-1) control drought control drought control drought control drought 0 54.11b 40.39d 2.1b 1.52c 9.94ab 6.41c 11.63c 4.74f 100 58.67ab 47.78c 2.47ab 1.72bc 10.1a 7.52bc 13.15b 6.09e 200 61.86a 52.94bc 2.66a 1.82bc 10.49a 8.76b 14.37a 7.75d lsd(0.05) 5.89 0.50 1.26 1.18 cv (%) 6.3 13.8 8.0 6.9 means followed by diverse letters differ significantly by lsd at p < 0.05. the obvious negative effect of drought condition also affects the 100-seeds weight noticeably. due to the drought condition in soybean plants, the 100-seeds weight of soybean had been declined by 35.51% compared to control condition (table 3). the maximum 100-seeds weight of soybean plants (10.49 g) was estimated into the 200 ppm of nano zno fertilizer treated plants in control condition. moreover, into this control level, 9.94 g of 100-seeds weight was also measured when the plants remained totally untreated. the lowest value of 100-seeds weight of soybean plant was only 6.41 g found into the untreated plants suffering from drought. whereas, the 100-seeds weight of 8.76 g was also observed in drought condition when the plants treated with 200 ppm nano zno fertilizer. the application of 100 and 200 ppm nano zno fertilizer incremented the 100-seeds weight of soybean plants in control condition by 1.51 and 5.53%, respectively compared to the untreated plants. the soybean under drought 80 dola et al. condition also manifested an increase of 100-seeds weight by 17.32 and 36.66%, due to the application of 100 and 200 ppm nano zno fertilizer, respectively compared to the untreated plants. the yield is one of the most vital components of any crop which defines the productivity of that crop. the average yield of soybean had been declined due to the adverse effect of drought condition by 59.24% compared to the control condition (table 3). the highest seed yield was 14.37 g plant-1 in 200 ppm of nano zno fertilizer treated plants in control condition. in control condition, only 11.63 g plant-1 yield was also calculated into the untreated plants. the lowest amount of yield was only 4.74 g plant-1 estimated into the drought affected plants which remained untreated. an increased yield of 7.75 g plant-1 was also found in drought condition, after the application of 200 ppm nano zno fertilizer. the application of 100 and 200 ppm nano zno fertilizer in control condition increased the yield by 13.07 and 23.56%, respectively compared to the untreated plants. in drought condition, the soybean plants treated with 100 and 200 ppm nano zno fertilizer depicted a raise by 26.79 and 63.50% of yield, respectively compared to the untreated plants. similar result was also found by vaghar et al. (2020) that under stressed conditions in the flowering, pod formation and seed filling stage, fe and zn nanochelates increased the number of grains plant-1, average seed yield of soybean by 43.8% and, reached the production rate of 2901.93 kg ha-1 more than other treatments. zn and mn foliar application increased the number of pods plant-1 by 23.2% compared with control (vaghar et al., 2020). in irrigation withheld conditions in pod formation, and seed filling stages, the treatment of zn and mn increased the number of pods plant-1 by 25.2%, and 20.6%, respectively compared to the control treatment. zn and mn treatment raised the 100-seed weight, where this increase was 16.5% higher than in the control. under stress conditions, it was 22% (vaghar et al., 2020). conclusion the growth, dry matter accumulation, and yield of soybean have been negatively impacted by the water deficiency condition. however, the negative effects of drought stress reduced when zno nanoparticles were applied as 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