2000 Volume 26 Issue 6 Pages 842-848
The behavior of pesticides (dymron, mefenacet, bensulfuron-methyl) was measured and simulated in a paddy field with rapid water penetration. In the field experiment, the concentration of each pesticide in paddy water reached a maximum shortly after its application, and then diminished rapidly to a non -detectable level within three days. In paddy soil, the concentrations of dymron and mefenacet in the topsoil (from soil surface to 5cm, 0-5cm) were much higher than those in the subsoil (5-10cm) four days after application, and their concentrations in both soils became almost the same after six days. On the other hand, a significant difference in the concentration of bensulfuron-methyl between the topsoil and the subsoil could not be observed. The behavior of pesticides in the paddy field was predicted well using a mathematical simulation model. It was found that transfer of pesticide with dissolution and penetration of water significantly contributed to the behavior of pesticides in paddy water, and the spatial distribution of the pesticides in paddy soil depended on the adsorbability of each pesticide. Dymron and mefenacet were shown to be spatially less mobile than bensulfuron-methyl because of their higher adsorbability.