Sorption of Sulfur in Highly Leached Humid Soils of North East India

Abstract

ABSTRACT High rainfall areas suffer from severe leaching loss of sulfate owing to their negatively charged nature. Sorption of sulfur (S) onto soil particles protect it from leaching out of the system. The S-sorption characteristics in humid soils from north-eastern India was studied with the objective to identify factors controlling S-sorption behavior in these acidic soils. Soils were collected from six different locations of north-eastern India. The soils were equilibrated with increasing concentrations of S for the sorption study, and later equilibrated with 0.01 N CaCl2 for desorption study. Results were fitted to three different isotherm models (Freundlich, Langmuir and Tempkin). The data fitted well to all three isotherm models. However, Freundlich adsorption isotherm yielded the best fit. Sorption parameters like S-sorption maxima (k), bonding energy (b), adsorption capacity (K), bonding energy constant (A) were positively correlated with the clay and, crystalline iron (Fe) and aluminum (Al) content in soil. Supply parameter increased with the increasing concentration of sulfate, while equilibrium buffering capacity was found decreasing. Soils from Nongpoh and Mustem with higher clay and crystalline Fe and Al content exhibited higher S-sorption capacity, whereas those of Padu having lowest clay content reported least S-sorption. It is recommended that in a soil having low S-sorption capacity, the minimal amount of S should be applied at a time.