Adsorption-desorption behaviour of clomazone in Regosol and Chernozem agricultural soils.

Studies of adsorption and desorption of pesticides by soils are important for understanding and predicting their fate and transport in the environment. Considering the agricultural and environmental relevance of clomazone, its sorption-desorption behaviour was studied in two widespread Serbian agricultural soil types named Regosol and Chernozem. Both phenomena are well-described by the Freundlich equation, which shows that clomazone is generally sorbed more to organic matter than to the mineral soil fractions. Chernozem, a soil containing more of both organic matter and clay, was found to bind more, and desorb less herbicide, than Regosol. Higher desorption hysteresis obtained for Chernozem could be attributed to its larger number of high-energy sorption sites, compared to Regosol. In both soils, the hysteresis effect increases with an increase in initial clomazone concentration in the soil-water system, while the percentage of desorbed amount during successive desorption cycles decreases. The presented adsorption-desorption study shows that soil composition plays an important role in clomazone behaviour and fate in the environment, and a significantly reduced probability of contamination of both the deeper soil layers and groundwater may be expected when this herbicide is found in humus-rich soils. [ABSTRACT FROM AUTHOR]