INFLUENCE OF ORGANIC-MATTER AND ITS CLAY COMPLEXES ON METOLACHLOR ADSORPTION ON SOIL

The absorption of metolachlor, 2-chloro-6'-ethyl-N-(2-methoxy-1-methylethyl) acet-o-toluidide was studied on three soils of various physical and chemical properties. Adsorption isotherms conformed to the Freundlich equation. The k(f) values increased with increasing organic carbon content of the soils. However, variations in k(oc) values by a factor of four were observed within three natural soils. For a given soil, the k(oc) values remained essentially unchanged after lowering the carbon content by hydrogen peroxide oxidation. These results suggest that the contribution of organic matter to total metolachlor adsorption process is influenced by association mechanisms between organic and inorganic soil constituents. Studies with mixtures of clay and organic matter indicate that the interaction between the two soil components reduces the surfaces available for metolachlor adsorption.