Metabolism of the Herbicide Diflufenican in the Soil of Field Wheat Crops

The fate of diflufenican (1) was studied in the soil of field wheat crops grown in different regions and during two crop seasons. Diflufenican soil metabolism was also studied in sugar beet replacement crops. When diflufenican was soil applied in the early spring, the time for 50% loss of initial diflufenican in soil was shorter than when it was applied in the autumn of the preceding year. The rate of diflufenican soil metabolism thus was greater during the spring/summer seasons than during the winter. The rate of diflufenican soil metabolism was also related to the climate. Diflufenican was transformed in soil into 2-[3-(trifluoromethyl)phenoxy]-3-pyridinecarboxylic acid (2), N-(2,4-difluorophenyl)-2-hydroxy-3-pyridinecarboxamide (3), and 2-hydroxy-3-carboxypyridine (4). No 2,4-difluoroaniline (5) or 3-(trifluoromethyl)phenol (6) was detected in the soil; no diflufenican (1), its metabolites 2-4, compounds 5 and 6 were detected in the wheat grain or in the root or leaves of the sugar beet.