CHANGES IN THE CONCENTRATIONS OF ISOPROTURON AND ITS DEGRADATION PRODUCTS IN SOIL AND SOIL SOLUTION DURING INCUBATION AT 2 TEMPERATURES

Changes in the concentrations of [C-14]carbonyl-isoproturon and its de gradation products in a clay-loam soil and in soil solution during inc ubation at 11-degrees-C and 18-degrees-C for 6 weeks, were measured fo llowing solvent extraction and soil solution sampling with glass micro fibre filters. During herbicide degradation, (CO2)-C-14 Was released ( up to 20%) and unextractable radioactivity increased (up to 30%). Mono methyl isoproturon was the main metabolite in soil followed by metabol ite X5 (Possibly hydroxy di-desmethyl isoproturon). Isoproturon and mo nomethyl isoproturon were mainly adsorbed by soil whereas metabolite X 5 was found mainly in the soil solution. Isoproturon concentrations de clined in both soil and soil solution, but the percentage of the resid ual herbicide dissolved in the soil solution decreased from 26 to 15%. At low temperature, herbicide degradation occurred more slowly, and t he degradation products were generally less abundant. However metaboli te X5 was present at unexpectedly high levels, particularly in the soi l solution.