Fractional dynamics and predictive modelling of soil sulphur in relation to physicochemical properties under calcareous soil condition of North Bihar

Abstract

This study aimed to evaluate the variability, interrelationships, and predictive modelling of different sulphur fractions in soils exhibiting a wide range of physicochemical characteristics. A total of twelve soil parameters, were analysed alongside five sulphur fractions: water-soluble (H₂O-S), inorganic sulphate (INORG-S), organic (ORG-S), residual (RES-S), and total sulphur (TOT-S). Descriptive statistics revealed that soils were predominantly alkaline (pH 8.11) and medium in organic carbon (0.70), with wide variability in nutrient content. ORG-S and RES-S constituted the dominant pools, while H₂O-S and INORG-S forms represented the readily available fractions. Pearson correlation analysis showed strong positive associations of sulphur fractions with organic carbon (OC), nitrogen (N), and micronutrients, and significant negative correlations with pH and CaCO₃. Stepwise multiple regression (SMR) model identified TOT-S, ORG-S, and RES-S as key predictors, with high coefficients of determination (R² ranging from 0.739 to 0.995), indicating robust inter-fractional relationships. The findings highlight the critical role of organic matter and soil reaction in regulating sulphur availability and partitioning.