Abstract
The concentrations and loadings of herbicides were investigated in three paddy field basins (4.7, 4.7 and 9.3 ha) from May to August 2002. The herbicide losses from the basins determined from cumulative load and application amount gathered by the questionnaire method were estimated to be 1.6% and 26% for Bromobutide, 8.9∼27% for Cafenstrol, 0.1% for Dimepiperate, 1.1∼2.0% for Mefenacet, 10.2∼25% for Simetryn, 0.9% and 14% for Thenylchlor, and 0.1∼1.6% for Thiobencarb. One of the important factors attributed to the differences in herbicide loss among the basins was water discharge from the basins. To generalize them, specific herbicide losses were calculated from herbicide losses and the height of daily dry weather flow. The specific herbicide losses suggested that transport with percolated water is the main factor for Cafenstrol and Simetryn losses, although other factors such as interaction with soil and degradation in soil may have also contribute to Bromotutide, Mefenacet, Thenylchlor and Thiobencarb losses from the paddy field basins.
