Reduced Herbicide Leaching by in Situ Adsorption of Herbicide–Micelle Formulations to Soils

Aiming to reduce herbicide leaching, "in situ" adsorption of herbicide-micelle formulations to soils was explored. Sulfentrazone or metolachlor were solubilized in cationic micelles, and these herbicide-micelle formulations were applied to sandy and alluvial soils. Sulfentrazone adsorption to the soils was negligible; however, its adsorption via its solubilization in micelles and their adsorption to the soil was significant and in good agreement with the Freundlich and Langmuir models. Adsorption of solubilized herbicide to the sandy soil was higher than to the alluvial soil. The low ratio between the surfactant concentration and the cation exchange capacity (CEC) of the alluvial soil brought upon micelle decomposition and reduction in herbicide adsorption. Therefore, an optimized ratio between surfactant and soil CEC was chosen to maximize herbicide retention. Even upon adding relatively low loadings of surfactant (0.075-0.3% w/w soil), herbicide leaching through the soils was significantly reduced (2-5-fold) in comparison with the commercial formulations.