Adsorption and mobility of metolachlor in surface horizons of soils with low organic matter content

The adsorption and mobility of metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)) acetamide were studied in 33 soils with low organic matter content from irrigated zones of the province of Salamanca, Spain. The adsorption constants K and the distribution coefficients Kd obtained from the Freundlich equation were used to compare the adsorption of metolachlor by the soils. For the study of mobility, the Rf values obtained by soil TLC were used. The simple correlation coefficients between K and Kd and the soil parameters indicate the existence of a very significant correlation (P < 0.01) of these constants with the organic matter content and a significant correlation (P < 0.05) with the silt + clay content. According to the Rf values found, metolachlor can be considered to be moderately mobile in 78.8% and mobile in 21.2% of the soils studied. The mobility of the herbicide is also related to the contents in organic matter and silt + clay of the soils.