SORPTION OF DINICONAZOLE AND METOLACHLOR BY 4 SOILS, CALCIUM-ORGANIC MATTER AND CALCIUM-MONTMORILLONITE

Diniconazole was sorbed by four soils in amounts 7 to 20 times that for metolachlor, by Ca-organic matter (Ca-OM) in amounts twice that for metolachlor, and by Ca-montmorillonite (Ca-Mont.) in amounts similar to metolachlor. Sorption of diniconazole greatly increased and desorption decreased from Ca-OM and Ca-Mont as solution pH decreased. Sorption by the soils, as indicated by Freundlich K values, were highly correlated with the organic carbon content of the soils for diniconazole and with organic carbon and clay contents of soils for metolachlor. Sorption of diniconazole was through physical sorption forces at neutral pH levels and was by way of cation exchange forces at low pH levels.