INFLUENCE OF SOIL PROPERTIES ON THE DEGRADATION OF THE NEMATOCIDE FENAMIPHOS

The decline and mincralization to (CO2)-C-14 of [phenyl-1-C-14]fenamiphos (f) together with the main metabolite fenamiphos sulfoxide (ox) was investigated over a period of 90 days, at two temperatures using 16 soils originating from different geographic areas (9 soils from a cool to temperate climate at 16-22-degrees-C and 7 soils from a subtropical to tropical climate at 22-28-degrees-C, resp.). The mineralization rates at 22-degrees-C, as determined by curve fitting, were in good correlation with the % C(mic)/C(org)-ratio (percentage of the microbial biomass in the total organic carbon content in the soil). The degradation rates for (f) plus (ox) could be described by first-order kinetics. The half-lives at 22-degrees-C ranged from 12 to 87 days. By means of a multiple computation, using regression analysis, between soil properties and decline rates it was possible to explain 70% of the total variance by differences in the pH (H2O)-values and in the % C(mic)/C(org)-ratio.