INFLUENCE OF APPLICATION METHODS ON THE DEGRADATION OF PERMETHRIN IN LABORATORY, SOIL AEROBIC METABOLISM STUDIES

The effects of application rate, volume, solvent and soil moisture con tent on the kinetics of mineralization and degradation, of [C-14]perme thrin have been studied in a sandy loam soil under standard laboratory conditions. During the incubation period, up to 32 days, the temperat ure and moisture level of the soil were controlled. Apart from the eff ects of application rate, which have been widely reported, application volume had the most significant effect on mineralization rate and T1/ 2. [C-14]Permethrin, at a level of a 1 mg kg-1 in the soil, applied in 100 mul of methanol, resulted in the evolution of 14% of the applied radiochemical as [C-14] carbon dioxide over 30 days. The same level ap plied in 1000 mul mineralized at a faster rate, with 30% [C-14]carbon dioxide evolved over 30 days. The test chemical applied to soil in met hanol mineralized at a significantly faster rate than a similar concen tration applied in ethanol. There was no significant difference when c omparing applications made using acetonitrile with those using methano l or ethanol. The addition of formulation ingredients resulted in litt le or no variation in mineralisation rate compared to an equivalent ap plication volume of methanol/water.