Abstract
In andosol upland field, leachate samples of six pesticides, pendimethalin, dimethoate, iprodione, linuron, acephate and prometryn were collected using the porous cup method during two years period. About 10mu;g/l of dimethoate was detected in the leachate from 50-70cm depth during a short period after the application, but its dissipation was rapid. Pendimethalin was detected at the low level. The leachate concentrations of iprodione and acephate differed markedly across two years. Linuron and prometryn were not detected in the leachate.
The pesticide residues in the surface soil were analyzed for acetone soluble fraction (ASF) and water soluble fraction(WSF). The WSF/ASF ratios of dimethoate, iprodione and linuron decreased with time, and the magnitude of corresponding ratios were in the same order with the leachate concentrations; dimethoate>iprodione>linuron (not detected). The half-lives (t1/2) of dimethoate and iprodione in the soil were dependent on temperature, but leachate concentrations were not effected. The leachate concentrations of dimethoate and acephate were higher in moist soil condition than in dry soil condition, but the reverse was obtained for iprodione. The leachate concentrations of above three pesticides were not dependent on the accumulative amount of rainfall. The leachate concentrations and soil residues of most pesticides were approximately the same between the plots with standard treatment and amended organic materials.
