Effect of soil amendments on the sorption behaviour of atrazine in sandy loam soil

Abstract The behaviour of pesticides applied during cultivation of crops is affected by usage of amendments like farm yard manure (FYM) and vermicompost (VC) during land preparation. Among pesticides, atrazine, a widely used herbicide in many crops, was analysed for its kinetics and sorption behaviour through the addition of FYM and VC in sandy loam soil. The pseudo-second order (PSO) model best fits kinetic results in the recommended dose of FYM and VC mixed soil. Atrazine was more sorbed onto VC mixed soil than FYM mixed soil during adsorption. Both FYM and VC (1, 1.5, and 2%) increased atrazine adsorption, but the effect varied with dosage and type of amendment. The Freundlich adsorption isotherm adequately explained atrazine adsorption in soil/soil+(FYM/VC) mixtures, and adsorption was highly nonlinear. The values of Gibb’s free energy change (ΔG) were negative for both adsorption and desorption, suggesting sorption was exothermic and spontaneous in nature. The results revealed that the application of amendments used by farmers interferes with the availability, mobility, and infiltration of atrazine in the soil. Therefore, the findings of this study suggest that amendments like FYM and VC can be effectively used to minimize the residual toxicity of atrazine treated ago-ecosystems in tropical and sub-tropical regions.