Herbicide and metabolite movement in different soils as studied by computer assisted microlysimeters

Leaching behaviour of the herbicides metamitron, metolachlor, and terbuthyl azine and some of their main metabolites has been studied in different soil s. A computerised microlysimeter apparatus was designed for observing the b ehaviour of those substances in soil cores under automated irrigation and c ontrolled water regime. Undisturbed soil columns from long-term no-tillage and plough tillage field plots were used, and varying irrigation intensitie s from 4 up to 10 mm/day were applied. Results suggest that an appropriate application of the herbicides according to the label will not result in the ir release via the leaching path, regardless of the tillage system which ca n determine physical, chemical, and biological conditions of the soil. Howe ver, higher application rates or spills cause excessive leaching losses whi ch can be explained by non-linearity of adsorption processes and non-equili brated conditions. Furthermore, the irrigation regime (C) 1999 Elsevier Sci ence Ltd. All rights reserved.