Effect of nitrogen and sulphur nutrition on yield parameters and protein composition in soybean [Glycine max (L.) Merrill].

Accumulation patterns of various protein fractions in seed, yield and protein quality parameters of soybean cultivar SL 525 harvested at different stages of development from plants grown under different treatments viz., nitrogen (urea @ 31.25 kg N ha -1 ), sulphur (gypsum @ 20 kg S ha -1 ) and combined application of nitrogen (N) and sulphur (S) were investigated. Application of S alone or combined with N significantly increased plant height, number of seeds per pod and total seed yield. Sulphur-containing amino acids viz., methionine and cysteine increased significantly (P ≤0.05) by all the treatments in comparison to control and maximum increase of 1.3 fold was observed by urea application. The contents of different protein fractions viz., albumin, globulin and glycinin (a subfraction of globulin) increased under the effect of N and S applied alone or in combination from 30 DAP to maturity with maximum accumulation at maturity as compared to control (without N or S application). Gypsum @ 20 kg S ha -1 resulted in higher accumulation of glycinin (11S) relative to β-conglycinin (7S) fraction of globulin protein in soybean seed thereby increasing 11S:7S ratio indicating improvement in soybean seed quality. The current study showed that improvement of soybean nutritional quality can be achieved by application of gypsum @ 20 kg S ha -1 along with