Forms of Sulphur and Evaluation to the Sulphur Test Methods for Moongbean in SometeraiSoils of Eastern India

Abstract

Surface soil samples of some terai soils of Eastern India were collected and analysed to evaluate different forms of sulphur status and soil test methods for predicting response of moong bean crop to sulphur application. The range of water soluble, sulphate, adsorbed, organic form and total sulphur were 6.91 to 26.23 (mean 16.69), 13.73 to 30.38 (mean 20.67), 3.19 to 42.91 (mean 18.37), 150.27 to 372.73 (mean 229.57) and 178.57 to 433.09 (mean 264.63) ppm, respectively. Soil pH, organic carbon, cation exchange capacity and total N content in soil were positively correlated to the all forms of sulphur. Although clay content was negatively correlated to water soluble and sulphate sulphur, but silt+clay content in soil was positively correlated to water soluble sulphur and negatively correlated to adsorbed sulphur content in these soils. Amongst the five chemical extractants employed, relative suitability of the extractants for predicting available sulphur status for these soils with reference to moong bean crop were in the order: Morgan > monocalcium phosphate 500ppm P > 0.15% CaCl2 > 1 N NH4OAc > 1% NaCl. Therefore, Morgan's extractant may be used as an index of available sulphur for moong bean (B1, Sonali) grown on acid soils of terai tract of Eastern India, the critical level being 18.0 mg kg−1.