Sorption of atrazine by soils of different agro-climatic zones of Karnataka

Sorption of atrazine by soils of different agro-climatic zones of Karnataka was studied using the batch equilibration technique. The sorption isotherm of atrazine was non-linear in all the soils, as depicted by the Freundlich exponent (n<1.0), indicating differential distribution of site energies for sorption. The Freundlich sorption coefficient (KF) values ranged from 4.26 to 6.08 in different soils and decreased in the order: Kathalagere>Mandya>Brahmavara>Hebbal, which is also the order of decreasing organic matter content in the soil. The coefficient of determination showed an improvement to 99 per cent using quadratic functions, suggesting thereby a better goodness of fit in predicting atrazine sorption compared to the linearised form of the Freundlich equation. The sorption of atrazine was increased with an increase in organic matter content, whereas clay content did not greatly affect sorption as indicated by a low regression coefficient. The net sorption constant (Kd) was significantly and positively correlated with the organic matter content of the soils.