ADSORPTION AND MOBILITY OF METOLACHLOR IN SURFACE HORIZONS OF SOILS WITH LOW ORGANIC-MATTER CONTENT

The adsorption and mobility of metolachlor ethyl-6-methylphenyl)-N-(2- methoxy-1-methylethyl)) acetamide were studied in 33 soils with low or ganic matter content from irrigated zones of the province of Salamanca , Spain. The adsorption constants K and the distribution coefficients K-d obtained from the Freundlich equation were used to compare the ads orption of metolachlor by the soils. For the study of mobility, the R( f) values obtained by soil TLC were used. The simple correlation coeff icients between K and K-d and the soil parameters indicate the existen ce of a very significant correlation (P < 0.01) of these constants wit h the organic matter content and a significant correlation (P < 0.05) with the silt + clay content. According to the R(f) values found, meto lachlor 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 r elated to the contents in organic matter and silt + clay of the soils.