55 RESEARCH PAPER J. Farm Sci., 33(1): (55-59) 2020 Effect of different nutrients and plant growth regulators on soybean productivity under assured moisture condition S. M. MANU, S. P. HALAGALIMATH AND H. T. CHANDRANATH Department of Agronomy, College of Agriculture, Dharwad University of Agricultural Sciences, Dharwad - 580 005, Karnataka, India E-mail: manusm@uasd.in (Received: November, 2019 ; Accepted: February, 2020) Abstract: A field experiment was conducted during to kharif 2017 to study the effect of nutrients and plant growth regulators on soybean productivity under assured moisture condition. The experiment was laid out using RCBD (factorial concept) with fertilizer levels (F 1 ): 100 % RDF (40:80:25 N:P 2 O 5 :K 2 O kg ha -1 ) and (F 2 ): 125 % RDF (50:100:31.2 N:P 2 O 5 :K 2 O kg ha -1 ); Plant growth regulators (G 1 ): Salicylic acid @ 50 ppm, (G 2 ): Salicylic acid @ 100 ppm, (G 3 ): Ethrel @ 100 ppm, (G 4 ): Ethrel @ 200 ppm, (G 5 ): Chlormequat chloride @ 250 ppm and (G 6 ): Chlormequat chloride @ 500 ppm; Controls (C 1 ): Independent control RPP-without plant growth regulator spray and (C 2 ): RPP + KNO 3 @ 1 % foliar spray. Results revealed that, 125 % RDF + chlormequat chloride @ 500 ppm sprayed at at 25 and 40 days after sowing (DAS) recorded significantly higher number of branches, number of leaves, total dry matter production, leaf area, leaf area index, number of pods, seed weight and yield as compared to other treatment combinations and control. The next best treatment combination which recorded significantly improved growth and yield parameters was 125 % RDF + ethrel @ 200 ppm. Key words: Chlormequat chloride, Ethrel, Salicylic acid, Soybean, Yield Introduction The soybean [Glycine max (L.) Merrill] is also called as “Golden Bean” or “Miracle crop” is a source of protein for human beings, animal feeds and many prepackaged meals. Soybean being a potentially high yielding crop can play a greater role in crop diversification by replacing rice in the existing cropping system (Dass et al., 2018). It is outstanding in its nutritive value with enhanced protein (40-42 %) and oil (20 %) content and is also rich in vitamins, minerals, salts and other essential amino acids. In addition to this, soybean protein has lysine (5 %), which is deficient in most of the cereals and enriching the cereal flour with the nutritive quality. Soybean is a major oil seed crop and occupies an area of 120.30 million hectare with production of 351.32 million tonnes and productivity of 2.92 t ha -1 (Anon., 2017). In India it is grown over an area of 11.25 million hectare with production of 11.73 million tonnes and productivity of 1042 kg ha -1 (Anon., 2018). In Karnataka soybean occupies an area of 0.29 million hectare with production of 0.24 million tonnes and productivity of 868 kg ha -1 (Anon., 2016). Soybean is characterized by prolific flower production with an extremely low proportion of pod set. The extent of flower shedding is said to be 60-92 % in soybean (Nahar and Ikeda, 2002), which causes low yield. Plant growth regulators are well known to improve the source-sink connection and encourage the translocation of photo-assimilates thereby helping in effective flower formation, fruit, and seed development and ultimately increase the yield of crops. Some of the growth regulators like salicylic acid, ethrel and chlormequat chloride (cycocel) may play a greater role to increase the seed yield of soybean. Salicylic acid is an endogenous growth regulator of phenol nature, which participates in regulation of physiological processes in plant, stomata closure, ion uptake, inhibition of ethylene biosynthesis, transpiration and stress tolerance (Khan et al., 2003). And also its application increase carbon dioxide (CO 2 ) and assimilation and photosynthetic rate, thus increasing dry matter. Ethylene released from ethrel (2-Chloro ethyl phosphonic acid) could possibly be utilized for promoting pod growth and early pod development in chickpea and tomato are related to higher ethylene levels, thus decreasing flower and pod shedding and thereby reducing abscission and improving better pod set. Ethrel induced increase in cell division, resulting in increased fruit size and yield have been reported in tomato fruits. Chlormequat chloride (CCC) or Cycocel is a plant growth regulator and known as antagonist of the plant hormone gibberellin. It acts by inhibiting gibberellin biosynthesis, reducing intermodal growth to give stouter stems, enhanced root growth, causing early fruit set and increasing seed set in plants. Thus, application of plant growth regulator is becoming a useful practice that has improved the yield of soybean. Keeping in view, a field experiment was conducted with an objective to know the effect of nutrient levels and plant growth regulators on growth, yield and economics of soybean. Material and methods A field study was conducted at University of Agricultural Sciences, Dharwad, Karnataka on medium deep black soil during kharif 2017. The experiment was laid out using randomized complete block design (factorial concept) with fertilizer levels (F 1 ): 100 % RDF (40:80:25 N:P 2 O 5 :K 2 O kg ha -1 ) and (F 2 ): 125 % RDF (50:100:31.2 N:P 2 O 5 :K 2 O kg ha -1 ); Plant growth regulators (G 1 ): Salicylic acid @ 50 ppm, (G 2 ): Salicylic acid @ 100 ppm, (G 3 ): Ethrel @ 100 ppm, (G 4 ): Ethrel @ 200 ppm, (G 5 ): Chlormequat chloride @ 250 ppm and (G 6 ): Chlormequat chloride @ 500 ppm; Controls (C 1 ): Independent