Sorption-desorption of imazamethabenz on three Spanish soils

Methyl imazamethabenz (methyl 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-4-yl)-p-toluate and m-toluate) is a weak acid herbicide used to control wild oats in cereal crops. This chemical has high soil persistence, which makes the study of the sorption-desorption processes of interest. Its kinetics and adsorption-desorption equilibria at different temperatures were determined in three agricultural soils using the batch equilibration technique. Kinetic profiles showed a two-step shape, with a fast initial adsorption until the first few hours followed by a slow adsorption during the rest of the whole range studied. Adsorption data conformed well to the Freundlich isotherm, with apparent increasing of adsorption with increasing of organic matter and clay content of the soils. The desorption process showed an important hysteresis phenomenon (i.e., nonreversible adsorption), which may affect imazamethabenz availability in soils.