Microsoft Word - BAJ 361C__Press Bangladesh Agron. J. 2020, 23(1): 91-99 POST-EMERGENCE WEED CONTROL OF STRIP-PLANTED WHEAT BY HERBICIDES T. Zahan1, M.R. Islam2, M.A. Hossain3, M.F. Hossain3, Q. Naher3, S. Ishtiaque1, and M.A. Ali4 1SO, 3SSO and 4CSO, On-Farm Research Division, BARI, Gazipur 2CSO, DG Office, BARI, Gazipur Corresponding E-mail: taslimazahan_tzp@yahoo.com (Received: 01April 2020, Accepted: 17 July, 2020) Keywords: Conservation agriculture, minimum tillage, productivity, weed management, wheat Abstract Transformation of a wheat field from conventionally heavy tillage to strip- planting is beneficial considering soil health improvement and savings in cultivation cost. Therefore, an experiment was conducted at the experimental field of On-Farm Research Division, Bangladesh Agricultural Research Institute, Gazipur during Rabi season of 2017-18 and 2018-19 to evaluate some available post-emergence herbicides for managing weeds in strip-planted wheat var. BARI Gom-30 and to find out the most effective post-emergence herbicide and its suitable rate for controlling weeds under strip tillage system. Three post- emergence herbicides (ethoxysulfuron, carfentrazone-ethyl plus isoproturon and carfentrazone-ethyl) were tested at their label rate and double of the label rate and their performance were compared with two times manual weeded control treatment. The study revealed that application of ethoxysulfuron at label rate and double of the label rate was effective for grass weed control, but not for broadleaf weeds. Application of carfentrazone-ethyl plus isoproturon both at label rate and double of the label rate was effective to control all types of weeds. Moreover, the highest grain and straw yields were recorded from label rate application of carfentrazone-ethyl plus isoproturon and its double rate application was also offered similar results in case of grain and straw yields. However; considering undetermined herbicide residual issue and having adverse effect on wheat leaves and finally on yield, the study discourages double of the label rate application of carfentrazone-ethyl plus isoproturon for managing weeds in wheat under strip tillage system. Introduction Intensive crop cultivation is seriously affecting health and quality of soil. Heavy tillage is considered as the major reason of soil erosion as well as soil quality depletion. Moreover, high cultivation cost is involved with heavy tillage because of using enough fuel and labour. On the other hand, strip tillage reduces cultivation cost as it requires less fuel, labour and saves time of cultivation (Hossain et al., 2015). Additionally, strip tillage reduces the rate of soil erosion compare to the conventional tillage because of less disturbance of soil. This minimum tillage also helps to preserve moisture in soil and it keeps soil micro-environment cool by practicing for long period (Salahin et al., 2017). Furthermore, wheat gives better yield and economic return under strip tillage than conventional system (Hossain et al., 2014). 92 Zahan et al. But weed is the major barrier to get targetable yield in the strip tillage system (Zahan et al., 2016). Now-a-days, unavailability and high wage of labour are diverting farmers to choose herbicides for weed control rather than manual weeding. Broadleaf weed infestation in wheat not only reduces the yield drastically but it also deteriorates the grain quality (Zand et al., 2007). To control broadleaf weeds, there are very few post-emergence herbicides are registered and available in the market of Bangladesh. Besides, the response of wheat varieties to different post-emergence herbicides might be different because of the genetic and physiological variability within the varieties (Punia et al., 1996). Therefore, an experiment was designed to evaluate weed controlling efficiency of some available post-emergence herbicides at different application rates in strip-planted wheat cv. BARI Gom-30 and to identify most suitable and effective herbicide for this new promising wheat variety. Materials and Methods The experiment was conducted at on-station field of On-farm Research Division, Bangladesh Agricultural Research Institute (BARI), Gazipur (23°59ˊ12.67567ˊˊ N and 90°24ˊ38.17521ˊˊ E) during Rabi season of 2017-18 and 2018-19. The soil of the experimental land was sandy in texture having low organic matter (1.41%) and soil pH 5.02. During the study period prevailing monthly average of maximum and minimum temperature and monthly total rainfall of the experimental site has been presented in Fig 1. Three post-emergence herbicides named ethoxysulfuron (early post-emergence), carfentrazone-ethyl plus isoproturon (late post- emergence) and carfentrazone-ethyl (late post-emergence) were evaluated at their label rate and double of the label rate comparing with a control treatment (manually weeded for two times at 20 and 40 days after sowing). The trade names of the used products of ethoxysulfuron, carfentrazone-ethyl plus isoproturon and carfentrazone-ethyl for the experiment were Sunrise 150WP,Affinity 50.75WP and Hammer 24EC, respectively. The experiment was laid out in RCB design with three replications. The unit plot size was 5 m x 3 m. Fig 1. Prevailed monthly maximum and minimum averaged air temperature and monthly total rainfall at BARI, Gazipur during November 2018 to April 2019 0 5 10 15 20 25 30 35 40 N ov '1 7 D ec '1 7 Ja n' 18 Feb '1 8 M ar '1 8 A pr '1 8 M ay '1 8 Ju ne'1 9 Ju ly '1 8 A ug '1 8 Sep t'1 8 O ct '1 8 N ov '1 8 D ec '1 8 Ja n' 19 Fe b'1 9 M ar '1 9 A pr '1 9 A ir T em p er a tu re (o C ) 0 50 100 150 200 250 300 350 400 450 R a in fa ll ( m m ) Tmax Tmin Rainfall Post-Emergence Weed Control of Strip-Planted Wheat 93 Previous crop, T. Aman rice was harvested by retaining 20 cm residue in the field. The field was weed-free; therefore, no pre-planting herbicide was applied. Seeds of wheat var. BARI Gom-30 were sown at the rate of 150 kg ha-1 by a two-wheel tractor driven strip planter within the strips apart by 20 cm on 21 November 2017 and 17 November 2018. Before strip till, the land was fertilized with phosphorus, potassium and sulphur in the form of triple super phosphate (TSP), muriate of potash (MoP) and Gypsum @ 160, 50 and 110 kg ha-1, respectively. All fertilizers were broadcasted in the field just before seeding wheat. Nitrogen fertilizer was applied in the form of Urea @ 200 kg ha-1 in two equal installments. First installment of urea was applied at 15 days after sowing (DAS) and the second one was at the spike initiation stage. Early post-emergence herbicide (ethoxysulfuron) was applied at 15 DAS and late post-emergence herbicides (carfentrazone-ethyl plusisoproturon and carfentrazone- ethyl) were applied at 25 DAS. Shallow irrigation was provided for four times to ensure proper germination and growth of wheat. Crop protection measures were also taken as and when necessary. Wheat was harvested on 19 March 2018 and 26 March 2019 at maturity. During 2019, crop required 11 days more to get maturity compared to the previous year because crop received heavy rainfall during February 2019 as well as March 2019 and the maturity period was delayed. Data on weed density and biomass were collected at 35 DAS from randomly selected two spots of 50cm×50cm sized quadrat. Weed species were also identified and weed population of each species was also counted. Data on yield contributing characters were recorded from randomly selected ten plants. Yield data were collected from the central 2m×3m area of each plot and converted in to t ha-1. The collected data were analyzed by using a statistical package program ‘R’ (version 3.3.3). Results and Discussion Effect of herbicides on weeds The wheat field was infested by seventeen (17) weed species during rabi season of 2017-18 among which four were grass weeds (Cynodon dactylon, Digitaria sanguinalis, Echinochloa colona and Elusina indica), one were sedges (Cyperus rotundus) and twelve broadleaf weeds (Polygonum hydropiper, Chenopodium album, Vicia virsuta, Physalis heterophylla, Enhydra fluctuans, Gnaphalium affine, Nicotiana plumbaginifolia, Portulaca oleracea, Eclipta prostrate, Amaranthus viridis, Alternanthera sessilis and Brassica kaber). During 2018-19, nine (09) weed species were identified among which five were grass weeds (Cynodon dactylon, Digitaria sanguinalis, Echinochloa colona, Elusina indica and Oryza rufipogon) and four (04) were broadleaf weeds (Enhydra fluctuans, Blumea lacera, Brassica kaber, Marsilea quadrifolia and Amaranthus viridis). The most infested weed species of strip planted wheat was Echinochloa colona during both years (Table 1). Grass weeds were dominant over other types of weeds (73% and 97% of the total infested weeds during 2017-18 and 2018-19, respectively). The study revealed that herbicide treatments reduced densities of all weed species at 35 days after sowing (DAS) compared to the control. In case of grass weeds, application of ethoxysulfuron at double of the label rate offered the highest density reduction in 2017-18 whereas carfentrazone-ethyl plus isoproturon at double of the label rate gave the highest in 2018-19 (Table 2). In case of broadleaf weeds, carfentrazone-ethyl plus isoproturon at double of the label rate provided the highest reduction in densities during both years. During 2017- 18, sedge weed were fully reduced by all herbicide treatments whereas this type of weed was absent in 2018-19. 94 Zahan et al. Table 1. Infested weed species in controlled plots of wheat at 35 days after sowing under strip tillage system in Gazipur during rabi season of 2017-18 and 2018-19 Weed species Local name Family Life cycle % infestation 2017-18 2018-19 Grass Cynodon dactylon Durba Poaceae Perennial 13.7 11.6 Digitaria sanguinalis Angulighas Poaceae Annual 13.6 25.8 Echinochloa colona Khudeshama Poaceae Annual 41.6 41.2 Elusina indica Chapra Poaceae Perennial 4.1 12.5 Oryza rufipogon Wild rice Poaceae Annual - 5.4 Sedge Cyperus rotundus Mutha Cyperaceae Perennial 2.1 - Broadleaf Polygonum hydropiper Biskatali Polygonaceae Perennial 4.3 - Vicia sativa Wild lentil/vetch Fabaceae Perennial 1.8 - Physalis heterophylla Foska begun Solanaceae Perennial 1.5 - Portulaca oleracea Nuneshak Portulaceae Perennial 2.5 - Eclipta prostrata Keshuti Asteraceae Perennial 1.8 - Chenopodium album Bathua Chenopodiaceae Perennial 3.2 - Gnaphalium affine Shetolomi/ Bon copi Asteraceae Perennial 3.2 - Nicotiana plumbaginifolia Bon tamak Solanaceae Perennial 1.2 - Enhydra fluctuans Helencha Asteraceae Perennial 2.1 1.6 Blumea lacera Shialmutra Asteraceae Perennial - 0.4 Amaranthus viridis Shaknotey Amaranthaceae Perennial 2.1 - Alternanthera sessilis Chanchi Amaranthaceae Perennial 1.2 - Marsilea quadrifolia Shushnishak Marsileaceae Perennial - 0.7 Brassica kaber Bon sharisha Brassicaceae Perennial - 0.8 Table 2. Effect of post-emergence herbicides on density reduction of weeds at 35 days after sowing of strip-planted wheat during Rabi season of 2017-18 and 2018-19 at on- station, OFRD, BARI, Gazipur Treatments % density reduction over control Grass weeds Sedge weed Broadleaf weeds 2017-18 2018-19 2017-18 2017-18 2018-19 Control - - - - - Ethoxysulfuron@RD 71.1 61.3 100 90.5 77.8 Ethoxysulfuron@2RD 76.4 72.0 100 95.8 88.9 Carfentra+isop@RD 52.9 72.7 100 83.9 100.0 Carfentra+isop@2RD 54.9 73.7 100 94.0 100.0 Carfentra@RD 53.1 59.6 100 88.1 11.1 Carfentra@2RD 60.2 66.6 100 96.4 55.6 Here, carfentra+isop = carfentrazone-ethyl + isoproturon, carfentra = carfentrazone-ethyl, RD = label rate, 2RD = double of the label rate Post-Emergence Weed Control of Strip-Planted Wheat 95 The study demonstrated that herbicide treatments had significant effect on total weed density and biomass at 35 DAS (Fig. 1). The highest number of weeds as well as the highest weed biomass was recorded from control plots during both years. The lowest weed density was counted from ethoxysulfuron at double of label rate application during 2017-18 and from double of the label rate application of carfentrazone-ethyl plus isoproturon during 2018-19. In case of weed biomass, the lowest weight was obtained from double rate application of carfentrazone-ethyl plus isoproturon during both years because of giving effective control on broadleaf weeds. Fig. 1. Effect of herbicides on (a) total weed density and (b) total weed biomass at 35 days after sowing of wheat under strip tillage system during 2017-18 and 2018-19 at on- station, OFRD, BARI, Gazipur. Effect of herbicides on wheat leaves The effect of the tested post-emergence herbicides on wheat was visually assessed from the day of herbicide application up to harvest. No herbicide had any visual effect on wheat except carfentrazone-ethyl plus isoproturon. In case of carfentrazone-ethyl plus isoproturon, bleaching was observed on leaves of wheat from 3 days of application and later on bleaching turned into leaf yellowing and necrosis. The chemical family of this late post-emergence herbicide is triazolinone plus urea and because of being the family member of urea the site of action of carfentrazone-ethyl plus isoproturon is inhibition of photosynthesis at photosystem II. That’s why; this herbicide had the bleaching effect on wheat leaves. But the fact is the length of the recovery period from adverse visual effect carfentrazone-ethyl plus isoproturon on wheat leaves. It was visually examined that wheat leaves recovered within 15 days after application (DAA) of carfentrazone-ethyl plus isoproturon at label rate; whereas those took 25-30 DAA to recovery at double of the label rate application (Fig. 2). 0 50 100 150 200 250 300 350 400 450 T o ta l w e e d d e n si ty ( n o . m -2 ) 2017-18 2018-19 p<0.001 at 35 DAS p<0.001 at 50 DAS (a) 0.0 10.0 20.0 30.0 40.0 50.0 60.0 T o ta l w e e d b io m a ss ( g m -2 ) 2017-18 2018-19 p<0.001 at 35 DAS p<0.001 at 50 DAS (b) 96 Zahan et al. Fig. 2. Effect of carfentrazone-ethyl plus isoproturon at (a) label rate and (c) double of the label rate on wheat leaves at 5 days after application (DAA) and at 20 DAA for (b) label rate application and for (d) double of the label rate application. Effect of herbicides on yield contributing characters and yield of wheat Herbicide treatments had significant effect on yield contributing characters as well as yield of strip-planted wheat during both years except spike length and grains spike-1 (Table 3 and Table 4). During both years, the highest number of tillers and heads m-2, grain yield and straw yield were obtained from carfentrazone-ethyl plus isoproturon at label rate of application and similar results except straw yield were also found from double rate application. The lowest numbers of tillers and heads m-2 and straw yield were recorded from control plots however the lowest grain yield was found from the double rate application of carfentrazone-ethyl. (a) (b) (c) (d) Post-Emergence Weed Control of Strip-Planted Wheat 97 Table 3. Effect of herbicides on yield and yield contributing characters of wheat under strip tillage system during 2017-18, Gazipur Treatments Tillers m-2 (no.) Spikes m-2 (no.) Spike length (cm) Grains spike-1 (no.) Grain yield (t ha-1) Straw yield (t ha-1) Control 280 d 272 d 15.6 34 3.86 c 4.69 c Ethoxysulfuron@RD 335 c 322 c 15.3 36 3.89 c 4.86 bc Ethoxysulfuron@2RD 348bc 337 c 15.7 36 4.04 bc 5.01 bc Carfentra+isop@RD 415 a 405 a 15.8 39 4.82 a 5.85 a Carfentra+isop@2RD 390ab 377ab 15.3 34 4.56 ab 5.19 b Carfentra@RD 360bc 347bc 15.6 37 4.22 bc 4.78 c Carfentra@2RD 350bc 328 c 14.9 34 3.81 c 5.00 bc Level of significance *** *** ns ns * *** CV (%) 6.97 6.60 5.14 9.34 8.08 3.93 In a column, means with similar letter(s) are statistically identical as per LSD0.05 Here, carfentra+isop = carfentrazone-ethyl + isoproturon, carfentra = carfentrazone-ethyl, CV = co- efficient of variance, *** = 0.1% level of significance, * = 5% level of significance, ns = non-significant Table 4. Effect of herbicides on yield and yield contributing characters of wheat under strip tillage system during 2018-19, Gazipur Treatments Tillers m-2 (no.) Spikes m-2 (no.) Spike length (cm) Grains spike-1 (no.) Grain yield (t ha-1) Straw yield (t ha-1) Control 239 d 236 e 17.5 45.3 2.63 e 3.83 d Ethoxysulfuron@RD 253 c 249 de 17.8 47.1 3.10 de 4.73 bc Ethoxysulfuron@2RD 255 c 255 cd 17.7 47.9 3.67 bc 4.90 b Carfentra+isop@RD 281 a 281 a 18.1 49.1 4.37 a 5.63 a Carfentra+isop@2RD 271 ab 271 ab 17.6 51.4 4.13 ab 5.10 b Carfentra@RD 266 b 262 bcd 17.7 48.7 3.20 cd 4.43 c Carfentra@2RD 271 ab 265 bc 17.9 49.4 3.13 cde 4.73 bc Level of significance *** *** ns ns *** *** CV (%) 2.42 2.92 2.60 5.84 8.79 5.22 In a column, means with similar letter(s) are statistically identical as per LSD0.05 Here, carfentra+isop = carfentrazone-ethyl + isoproturon, carfentra = carfentrazone-ethyl, CV = co- efficient of variance, *** = 0.1% level of significance, * = 5% level of significance, ns = non-significant Economic Analysis The results showed that plots with recommended dose of carfentrazone-ethyl plus isoproturon had the highest gross return as well as the highest gross margin (Table 5). The lowest gross return and gross margin were calculated from the control plots and the reason was related to the high cost involvement for manual weeding. 98 Zahan et al. Table 5. Cost effectiveness of herbicides in strip-planted wheat during 2017-18 and 2018-19 at Gazipur Treatments 2017-18 2018-19 Total cost of production (Tk. ha-1) Gross return (Tk. ha-1) Gross margin (Tk. ha-1) Total cost of production (Tk. ha-1) Gross return (Tk. ha-1) Gross margin (Tk. ha-1) Control 56770 82833 26063 56070 82833 26763 Ethoxysulfuron@RD 43395 97733 54338 42695 97733 55038 Ethoxysulfuron@2RD 44295 114900 70605 43595 114900 71305 Carfentra+isop@RD 45390 136633 91243 44690 136633 91943 Carfentra+isop@2RD 48285 129100 80815 47585 129100 81515 Carfentra@RD 43211 100433.3 57222 42511 100433 57922 Carfentra@2RD 43926 98733.2 54807 43226 98733 55507 Market price (Tk. ha-1) of commercial herbicides: pendimethalin = 2525, ethoxysulfuron @ RD = 900, ethoxysulfuron @ 2RD = 1800, carfentrazone-ethyl+isoproturon @ RD = 2895, carfentrazone- ethyl+isoproturon @ RD = 5790, carfentrazone-ethyl = 716, carfentrazone-ethyl = 1431 Manual weeding cost (Tk.): 50labours ha-1 for 2 times weeding (in weed-free check) @ 350 labour-1 day-1, Herbicide application cost (Tk.): 1labour ha-1 round-1 @ 350 labour-1 day-1, Irrigation cost (Tk.): 6labours ha-1 for 3 times irrigation during 2017-18 and 4 labours ha-1 for 2 times during 2018-19 @ 350 labour-1 day-1, Harvest and post-harvest processing cost (Tk.): 45 labours ha-1 @ 350 labour-1day- 1, Market price of grain (Tk. 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