Effect of Plant Growth Regulators and Their Time of Application on Yield Attributes and Quality of Soybean

Plant growth regulators play important roles in plant growth and development, but little is known about the roles of plant growth regulators in yield components and seed qualities of soybean. In this study, salicylic acid, gibberellic acid (GA3), kinetin and distilled water (control) were sprayed to soybean (BARI Soybean-6) at the vegetative stage, flower initiation stage, pod initiation stage, flower + pod initiation stage in the pot experiment under field condition during November, 2013 to March, 2014. Treatments were arranged in a Randomized Complete Block Design (RCBD) with five replications. The different plant growth regulators and their time of application showed significant effect on number of pods plant-1, pod length, number of seeds pod-1, 100-seed weight, stover yield, biological yield, harvest index, seed grading (% by weight), protein and moisture content in seed of soybean. Salicylic acid gave the highest number of seeds pod-1, harvest index, small size seed, protein and moisture content in seed (1.60, 39.06%, 19.47%, 44.56% and 12.91%, respectively). Kinetin spray produced the maximum 100-seed weight (11.58 g). Application of growth regulators at vegetative stage produced the highest stover yield (6.46 g plant-1), flower initiation stage gave the larger size seed (59.09%), pod initiation stage showed the maximum pod length (2.43 cm), highest moisture content in seed (13.50%) and spray at flower + pod initiation stage produced the maximum 100-seed weight (12.00 g), harvest index (43.42%), medium size seed (32.53%), protein content in seed (44.31%). Among the treatment combinations the application of salicylic acid at flower and pod initiation stage showed the highest yield attributes and maximum protein content compared to those of other growth regulators.