Bangladesh Agron. J. 2020, 23(2): 111-117 GROWTH, FLOWER DROPPING, POD SET AND YIELD RESPONSE OF SOYBEAN VARIETIES AS AFFECTED BY SUPLEMENTAL FERTILIZER SPRAY AT FLOWERING N. Chakma, P.K. Biswas and M. Hasanuzzaman Department of Agronomy, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh Corresponding E-mail: nidhichakma045@gmail.com (Received: 17 October, 2020, Accepted: 04 December, 2020) Keywords: Foliar spray, Urea, MoP, DAP, flower and pod dropping, yield, soybean Abstract A field experiment was conducted during the period from January to May 2014 to study the response of growth, flower dropping, pod setting and yield of two soybean varieties to foliar fertilization of urea at early stage of flowering. Soybean varieties, BARI Soybean-5 and BARI Soybean-6, were feeded with four supplemental foliar spray treatments of fertilizer, viz. M1: Control i.e., no additional nutrient spray; M2: 20% of recommended urea spray at flowering; M3: 20% dose of the recommended MoP; and M4: 20% dose of the recommended DAP at early flowering stage. The experiment was laid out in a split- plot design with three replications. There was no significant effect of variety, fertilization spray or their interaction observed on growth parameters. However, flower and pod dropping was affected with higher flower dropping (55.2%) in BARI Soybean-5 and maximum pod dropping (16.44%) with DAP spray treatment. Higher yield attributes’ values such as seeds pod -1 (2.42), seed yield (1.18 t ha -1 ), stover yield (1.02 t ha -1 ), and biological yield (2.21 t ha -1 ) were obtained with foliar DAP spray treatment. The interaction of BARI Soybean-5 and foliar DAP spray showed the highest seed yield (1.48 t ha -1 ), stover yield (1.26 t ha -1 ) and biological yield (2.75 t ha -1 ). Introduction Soybean is the most important oil seed crop in the world, which belongs to Fabaceae family. The crop not only provides oil, it also supplies vegetable protein to millions of people. The multipurpose use of soybean is gradually increasing day by day in Bangladesh thus the cultivated area of soybean also increasing. The area harvested for soybean in Bangladesh was above 62000 ha and the production was 96921 ton with average yield of 1.5 t ha -1 . However, the world average yield of soybean was about 2.9 t ha -1 (FAOSTAT, 2018). The reason for low yield rate of soybean is mainly due to use of low yielding varieties and insufficient agronomic management (Khanam et al., 2016). Experimental evidences reveal that soybean is highly responsive to different fertilizers and its yield can be increased remarkably through the judicious fertilization (BARI, 1988; Mohamed, 1984; Kazi et al., 2002). Soybean yield depends on number of pods produced per unit area and seed weight. The number of pods depend on the number of floral buds which attain maturity. Although the crop produces abundant flowers, but a large proportion of them drop away during development (Kokubun, 2011). According to Shibles et al. (1975), the flower and pod dropping rate were estimated to reach 80%. Reduction of flower and pod dropping rate is an important factor in increasing yield of soybean. Generally, essential plant nutrients are applied as a basal dose during land preparation to attain maximum yield of a crop. Although soil application is the most effective method, but under some circumstances foliar fertilization is more effective and economic (Fageria et al., 2009). 112 Chakma et al. Foliar spraying is helpful when crop roots are unable to provide enough nutrients and much more economic since foliar application rate is less compared to soil application. Many researchers reported that supplemental nutrients applied at different reproductive stages of crop through foliar application increases the yield of soybean. Specially, at early flowering or pod initiation stage, soybean requires more nutrients for the development of pod and seed along with optimum soil moisture (Dandge et al., 2018). It is suggested that nitrogen (N) is the determinant of seed production for crops with high seed N content (Kinugasa et al., 2012). Rigorous researches are still necessary to identify and specify the right nutrients for highest potential yield of soybean. The experiment was undertaken to investigate the influence of foliar nutrient spray on flower and pod droppings of soybean, and to study the growth and yield response of two soybean varieties towards urea, MoP and DAP spray at early flowering stage. Materials and Methods The experiment was carried out at research field of Agronomy department, Sher-e-Bangla Agricultural University, Dhaka during the period of Jan-May, 2014. The soil of the experimental site is belonged to the Modhupur tract (AEZ No. 28). The topography of the experimental site was adequately uniform, leveled and soil was deep red brown terrace soil with pH 5.6. The full amount of recommended dose @ 60, 175, 120, 115 and 10 kg ha -1 of Urea, Triple super phosphate (TSP), Muriate of potash (MoP), gypsum and boric acid respectively (FRG, 2012) were applied during final land preparation. Two soybean varieties, BARI Soybean-5 and BARI Soybean-6 were used for this experiment. The experiment consisted two factors and it was laid out in a split-plot design with three replications. Total number of plots was 24 and the size of each unit plot was 3m  3m. Two soybean varieties were assigned in the main plot, V1: BARI Soybean-5 and V2: BARI Soybean-6 and the sub-plots had four supplemental spray treatments, M1: Control (no additional nutrient spray); M2: 20% of recommended Urea spray at flowering; M3: 20% of recommended MoP spray at flowering and M4: 20% of recommended DAP spray at flowering. The supplemental spray was done at flowering stage (60 days after sowing). Different intercultural operations such as thinning, irrigation, weeding and plant protection measures were done as and when needed. Five plants from each plot were randomly selected and different growth parameters (plant height, leaflet number, branches plant -1 and dry matter plant -1 ) were recorded at 75 DAS and 100 DAS. Another five plants were randomly selected for documenting flower and pod dropping rate by using a clean paper. The harvesting was done when 90% of the pods become brown in color and the plants were harvested from 5.4 m 2 central area of each plot. Yield attributes such as no. of pods plant -1 , no. of seeds pod -1 , grain yield, stover yield and harvest index were recorded at the time of harvesting. The collected data were statistically analyzed by using Statistix 10 statistical program and the significant differences were compared by the least significant difference (LSD) test at 5% level of probability (Gomez and Gomez, 1984). Results and Discussion Growth parameters The growth parameters of two soybean varieties didn’t show any significant variation in regards of effect of variety, fertilization, and interaction of variety x fertilizers at 75 DAS and 100 DAS (Table 1). While in terms of variety, BARI Soybean-5 performed comparatively better for plant height (57.57 cm and 58.67 cm) and branch number plant -1 (4.03 and 3.62), highest dry weight plant -1 (7.59 g and 15.17 g) was recorded in BARI Soybean-6 at 75 DAS and 100 DAS, respectively. Among the fertilizer treatments, DAP fertilization (M4) showed highest plant height (55.69 cm and 58.42 cm) at 75 DAS and 100 DAS, highest branch number plant -1 (3.83) and dry weight plant -1 (16.92) at 100 DAS. In Growth, Flower Dropping, Pod Set and Yield Response of Soybean 113 terms of the interaction effect of variety and fertilization, V1M4 (BARI Soybean-5 and DAP) presented highest plant height and branch number plant -1 at 75 DAS and 100 DAS, and V2M4 (BARI Soybean-6 + DAP) produced highest dry matter plant -1 at 100 DAS. It seems that the combination of nitrogen and phosphorous fertilizer showed better result in soybean plants growth traits. A similar foliar spray was performed by Kaur and Singh (2019) at pod initiation stage with the treatments of water, urea, Mop, DAP, NPK 19:19:19, molybdenum and zinc spray, and similarly, the treatments didn’t significantly influence the growth attributes of soybean. Table 1. Effect of foliar urea, MoP and DAP spray on different growth parameters of soybean at 75 DAS and 100 DAS Treatments Plant height (cm) Leaflet numbers plant-1 Branch number plant-1 Dry weight plant-1 (g) 75 DAS 100 DAS 75 DAS 100 DAS 75 DAS 100 DAS 75 DAS 100 DAS Variety V1 57.57 58.67 70.36 24.57 4.03 3.62 6.61 11.71 V2 50.11 52.23 64.40 25.50 3.62 3.42 7.59 15.17 Foliar spray M1 54.68 56.23 71.50 27.60 3.90 3.33 6.62 12.40 M2 53.00 54.68 69.87 23.60 4.03 3.50 7.09 11.51 M3 51.97 52.47 62.50 23.13 3.53 3.40 7.82 12.92 M4 55.69 58.42 65.64 25.80 3.83 3.83 6.87 16.92 SE 4.70 4.38 11.46 3.61 0.66 0.54 1.32 3.21 Variety x Foliar spray V1M1 59.09 60.80 74.40 29.80 3.93 3.20 6.09 11.46 V1M2 56.47 58.47 73.33 22.27 4.27 3.80 5.68 9.64 V1M3 54.58 54.40 63.80 19.93 3.60 3.27 8.51 8.94 V1M4 60.14 61.00 69.89 26.27 4.33 4.20 6.16 16.79 V2M1 50.28 51.67 68.60 25.40 3.87 3.47 7.15 13.35 V2M2 49.54 50.90 66.40 24.93 3.80 3.20 8.51 13.38 V2M3 49.37 50.53 61.20 26.33 3.47 3.53 7.12 16.89 V2M4 51.25 55.83 61.40 25.33 3.33 3.47 7.58 17.05 SE 6.65 5.66 16.20 4.47 0.99 0.75 1.71 5.34 CV (%) 15.12 13.67 29.45 25.00 30.04 26.79 32.25 41.41 V1 = BARI Soybean-5, V2 = BARI Soybean-6, M1 = No Supplemental spray, M2 = Supplemental spray of Urea, M3 = Supplemental spray of MoP, M4 = Supplemental spray of DAP Flower and pod dropping In case of flower and pod dropping attributes, flower dropping and pod dropping displayed significant variation for two varieties and fertilizer treatments respectively. There was no statistically significant variation found among soybean variety and fertilization interaction (Table 2). The maximum flower dropping (%), pod dropping (%), and total pod dropping (%) was recorded under BARI Soybean-5 (55.2, 15.36, and 70.56 respectively). Although, highest flower dropping % (55.30) was found under urea treatment (M2), maximum pod dropping % and subsequently total dropping % (16.44, and 68.99, respectively) was found in DAP treatment (M4). The highest remaining pod was found under MoP treatment (M3). Oko et al. (2003) reported reduced flower abortion rate in soybean when foliar urea was applied at reproductive stages compared to control. Roy (2013) reported minimum flower dropping and pod dropping under supplemental irrigation + N spray before flowering 114 Chakma et al. in chickpea. The result inconsistency might be due to differences in variety, soil moisture availability and subsequent treatments. Table 2. Effect of foliar urea, MoP and DAP spray on flower and pod dropping percentage of two soybean varieties Treatments Flower dropping (%) Pod dropping (%) Total dropping (%) Pod remaining (%) Variety V1 55.2 a 15.36 70.56 29.45 V2 50.89 b 13.89 63.87 35.96 Foliar spray M1 52.61 14.22 ab 66.83 32.84 M2 55.3 12.93 b 68.24 31.76 M3 51.73 14.93 ab 64.82 35.22 M4 52.56 16.44 a 68.99 31.01 SE 3.78 1.12 4.38 4.42 Variety x Foliar spray V1M1 55.36 16.31 71.67 28.33 V1M2 55.77 12.58 68.35 31.65 V1M3 52.81 16.66 69.47 30.59 V1M4 56.87 15.89 72.77 27.23 V2M1 49.86 12.13 61.98 37.35 V2M2 54.83 13.29 68.13 31.87 V2M3 50.64 13.19 60.16 39.84 V2M4 48.24 16.98 65.22 34.78 SE 4.65 3.63 6.1 6.21 CV (%) 12.35 13.27 11.29 23.41 V1 = BARI Soybean-5, V2 = BARI Soybean-6, M1 = No Supplemental spray, M2 = Supplemental spray of Urea, M3 = Supplemental spray of MoP, M4 = Supplemental spray of DAP Maximum flower dropping and total dropping was found in V1M4 (BARI Soybean-5 x DAP spray) and consequently, minimum pod remaining was found in the same interaction. The lowest total dropping was recorded under V2M3 (BARI Soybean-6 + MoP) and consequently, maximum remained was found under same interaction (Table 2). Yield and yield attributes Among the yield attributes, pod length, seed yield and biological yield showed significant differences for two soybean varieties, while other yield attributes didn’t show any significant differences (Table 3). The higher pods number plant -1 and harvest index was recorded in BARI Soybean-6 and higher pod length (cm), seeds pod -1 , 1000-seed weight, seed yield, stover yield and biological yield was found in BARI Soybean-5. Among the fertilizer treatments, seeds pod -1 and 1000-seed weight showed significant differences for different foliar fertilization at early flowering stage. The highest pods number plant -1 (57.72), pod length (3.47 cm), and harvest index % (59.01) was recorded under MoP treatment (M3), however, highest number of seeds pod -1 , highest stover yield, and biological yield was found in DAP treatment (M4). A similar result was obtained by Vinoth Kumar et al. (2013), where highest number of pods plant -1 , number of seeds pod -1 , grain yield was recorded under 2% DAP treatment. Singh et al. (2018) Growth, Flower Dropping, Pod Set and Yield Response of Soybean 115 also performed a similar experiment at pod initiation stage and reported highest pods plant -1 and seed yield under 2% DAP spray. The interaction effect of variety and fertilizer showed statistically significant differences in seeds pod -1 , pod length, seed yield, and biological yield. The maximum seeds pod -1 (2.48) was recorded from V1M3 (BARI Soybean-5 + MoP) which was statistically similar (2.43) to V1M4 (BARI Soybean-5 + DAP). On the other hand, maximum seed yield (1.48 t ha -1 ) and biological yield (2.75 t ha -1 ) was recorded from V1M4 (BARI Soybean-5 + DAP at flowering). The harvest index didn’t show any significant variation among interaction treatments; however, maximum harvest index was found from V2M2 (BARI Soybean-6 + Urea spray at early flowering). Table 3. Effect of foliar urea, MoP and DAP spray on yield attributes of two soybean Varieties Treatments Pods plant-1 (No.) Pod length (cm) Seeds pod-1 (No.) 1000- seed weight (g) Seed yield (t ha-1) Stover yield (t ha-1) Biological yield (t ha-1) Harvest index (%) Variety V1 50.33 3.51 a 2.41 103.47 1.29 a 1.03 2.32 a 55.56 V2 60.45 3.36 b 2.36 95.9 0.95 b 0.71 1.66 b 57.38 Foliar spray M1 55.67 3.44 2.33 c 104.04 a 1.03 0.81 1.84 55.37 M2 54.43 3.43 2.37 b 102.39 ab 1.21 0.91 2.11 57.94 M3 57.72 3.47 2.41 ab 96.59 b 1.07 0.73 1.79 59.01 M4 53.73 3.41 2.42 a 95.74 b 1.18 1.02 2.21 53.54 SE 9.24 0.04 0.02 3.13 0.19 0.14 0.29 3.24 Variety x Foliar spray V1M1 53.73 3.44 bc 2.29 d 111.33 1.17 ab 0.91 2.08 ab 55.01 V1M2 46 3.49 b 2.42 b 104.33 1.28 ab 1.13 2.40 ab 53.47 V1M3 56.23 3.68 a 2.48 a 98.66 1.21 ab 0.82 2.03 ab 59.35 V1M4 45.33 3.41 bc 2.43 ab 99.57 1.48 a 1.26 2.75 a 54.41 V2M1 57.6 3.44 bc 2.37 b 96.74 0.88 b 0.71 1.59 b 55.74 V2M2 62.87 3.36 cd 2.33 cd 100.44 1.13 ab 0.69 1.81 b 62.42 V2M3 59.2 3.25 d 2.34 cd 94.52 0.92 b 0.64 1.56 b 58.67 V2M4 62.13 3.41 bc 2.4 b 91.91 0.87 b 0.78 1.66 b 52.58 SE 13.42 0.05 0.03 4.42 0.23 0.21 0.38 5.74 CV (%) 28.91 1.87 1.39 5.43 28.85 27.2 26.03 9.94 V1 = BARI Soybean-5, V2 = BARI Soybean-6, M1 = No Supplemental spray, M2 = Supplemental spray of Urea, M3 = Supplemental spray of MoP, M4 = Supplemental spray of DAP Conclusion In conclusion, it appears that foliar application of urea, MoP and DAP at early flowering stage had no significant effect on plant growth traits of soybean. In case of flower & pod dropping and yield attributes, the results showed inconsistency with previous findings of other researchers. It is suggested that further study is required before recommending foliar nutrient application for optimum soybean production. 116 Chakma et al. References BARI (Bangladesh Agricultural Research Institute). 1988. Annual Report 1988-1989. BARI, Joydebpur, Gazipur-1701, Bangladesh. Dandge, M.S., Y.V. Ingle, P.D. Peshattiwar and H.H. Dikey. 2018. Effect of foliar nutrition on soybean productivity. Intl. J. Chem. Stud. 6(1): 1290-1292. Fageria, N.K., M.P. Barbosa Filho, A. Moreira and C.M. Guimaraes. 2009. Foliar fertilization of crop plants. J. Plant Nutr. 32(6): 1044-1064. FAOSTAT. 2018. World Food and Agriculture - Statistical Pocket Book 2018. Rome. p.254. FRG. 2012. Fertilizer Recommendation Guide. Bangladesh Agricultural Research Council (BARC), Farmgate, Dhaka-1215, Bangladesh. p.274. Gomez, A.A. and K.A. Gomez. 1984. Statistical Procedures for Agricultural Research, John Wiley and Sons, Ink., New York. pp.207-215. Kaur, V.H. and G. Singh. 2019. Effect of foliar fertilization at early reproductive stages on growth, productivity and profitability of soybean (Glycine max (L.) Merrill). Appl. Biol. Res. 21(3): 250- 254. Kazi, B.R., F.C. Oad and A. Lakho. 2002. Effect of irrigation frequencies on growth and yield of soybean. Pakistan J. Appl. Sci. 2(6): 661-662. Khanam, M., M.S. Islam, M.H. Ali, I.M. Chowdhury and S.M. Masum. 2016. Performance of soybean under different levels of phosphorus and potassium. Bangladesh Agron. J. 19(1): 99-108. Kinugasa, T., T. Sato, S. Oikawa and T. Hirose. 2012. Demand and supply of N in seed production of soybean (Glycine max) at different N fertilization levels after flowering. J. Plant Res. 125: 275-281. Kokuban, M. 2011. Physiological Mechanisms Regulating Flower Abortion in Soybean. In: Soybean- Biochemistry, Chemistry and Physiology, DOI: 10.5772/15694. Mohamed, S.A. 1984. Effect of irrigation and water use efficiency of corn plants in Fayoum Governrate. Ann. Agric. Sci. 20(2): 221-235. Oko, B.F.D., A.E. Eneji, W. Binang, M. Irshad, S. Yamamoto, T. Honna and T. Endo. 2003. Effect of foliar application of urea on reproductive abscission and grain yield of soybean. J. Plant Nutr. 26(6): 1223-1234. DOI: 10.1081/PLN-120020366 Roy, I. 2013. Influence of supplementary nitrogen, irrigation, and hormones on flower droppings, growth and yield of chickpea. Masters Thesis. Sher-e-Bangla Agricultural University, Dhaka, Bangladesh- 1207. Singh, A.K., C.S. Singh, A.K. Singh and S. Karmakar. 2018. Soybean productivity as influenced by foliar application of nutrients. J. Pharmacog. Phytochem. SP1: 413-415. Shibles, R.M., I.C. Anderson and A.H. Gibson. 1975. Crop Physiology (Evans, L.T., ed.) Cambridge University Press, London, pp.151-190. Van Roekel, R.J., L.C. Purcell and M. Salmeron. 2015. Physiological and management factors contributing to soybean potential yield. Field Crops Res. 182: 86-97. Vinoth Kumar, C.K. Vaiyapuri, A.M. Mohamed and G. Gopalswamy. 2013. Influence of foliar spray of nutrients on yield and economics of soybean (Glycine max L. Merill). J. Biol. Sci. 13: 563-565. https://www.researchgate.net/deref/http%3A%2F%2Fdx.doi.org%2F10.5772%2F15694