Sulfur accumulation in Vertisols due to continuous gypsum application for six years and its effect on yield and biochemical constituents of soybean (Glycine Max L. Merrill)

Abstract

Application of S through inorganic sources is recommended to the crops in the cropping system in S deficient soils of India. However, transformations of S in the soil profile following continuous gypsum application are not known. The accumulation of S into different fractions due to application of a total of 180—540 kg S ha—1 over a six-year-period in soybean — wheat cropping system and its effect on the yield and quality of soybean produce were investigated in a vertisol area. About 25—38% of the S added was retained in the 90 cm depth of profile. Significant changes in the total S content in soil layers were recorded wherein a total of 360 kg S ha—1 or more S was applied. Maximum increase in total S content was recorded in upper layers. Soluble S accumulated more in the 30—75 cm depth; whereas, proportion of sorbed fraction of S increased with depth. Build up of S in the surface layer of the profile was mostly related to the increase in organic fraction. The S accumulation in lower layers of the profile was mostly due to increase in soluble and sorbed fractions of S. Such an increase of the S content in the soil caused an increase in seed yield, uptake of S as well as content of oil and S containing amino acids, cystine, and methionine in seed of soybean crop.