Vertical Distribution of Forms of Sulphur in Relation to Physicochemical Properties of Lateritic Soils of Eastern India

Sulphur (S) deficiency is widespread in Indian soils, and it has been emerging as a major problem in rice-growing lateritic soils of West Bengal. The vertical distribution of S forms and their relationships with soil physicochemical properties were examined in 50 rice-growing locations of lateritic soils of West Bengal, India, for the current study. For this a total of one hundred fifty representative soil samples were collected from three depths and fifty representative locations of rice-based cropping systems of lateritic belt of West Bengal and analyzed for different fractions of S and important physicochemical properties using standard methodology. Most soils were sandy clay loam to clay loam, with low to medium levels of organic carbon, and strongly acidic to moderately acidic. A decrease in organic carbon across the depths was evident. Among the sulphur forms, organic S was dominant, and the contribution of water-soluble S was least throughout the soil profile. The studied sulphur forms followed the order: total S > organic S > heat soluble S > adsorbed S > sulphate S > water soluble S. Except for adsorbed S, most forms decreased with soil depth. The correlation study revealed that soil pH was positively and significantly correlated with water soluble (r = 0.431**) and sulphate S (r = 0.325*) in surface soils, with sulphate S both in mid-surface (r = 0.450**) and subsurface soils (r = 0.423**). Organic carbon showed a positive correlation with all the S forms throughout the profile. Both clay and silt content positively affected S forms, while sand content showed a negative relationship. Positive correlation among all the S forms observed along soil depth, except for a negative correlation between adsorbed S and sulphate S. This investigation will be helpful for sulphur management to optimize crop yields in lateritic soils.