Effect of Organic Manure Application on Adsorption-Desorption of Isoproturon Herbicide in Different Soils

The effect of organic manure application on adsorption-desorption characteristics of isoproturon was studied on four different soils, two each from Rampur and Majhera. Addition of farmyard manure increased soil organic C content and electrical conductivity but decreased soil pH, especially in case of alkaline alluvial plain soils (Rampur). The adsorption-desorption data of isoproturon conformed to Freundlich isotherm equation. Application of FYM increased distribution coefficient (K_d), desorption capacity (logK’) but decreased 1/n’. The desorption index (n’/n) also showed an increase at higher rates of FYM indicating less reversibility of isoproturon. Distribution coefficient of isoproturon adjusted for soil organic carbon (K_OC) showed a significant positive correlation with soil pH but negatively correlated to soil organic C content. The adsorption capacity (log K) of isoproturon showed a significant positive correlation with soil organic carbon content but a negative correlation with soil pH and CaCO₃. The slope factor (1/n) was positively related to soil pH, EC and CaCO₃.