TRANSFORMATION OF [DICLOFOP-METHYL-C-14 IN SMALL FIELD PLOTS

The degradation of the herbicidal ester [14C]diclofop-methyl, in soil, applied at a rate of 1.25 kg/ha, was studied under field conditions in small sandy loam plots. The plots, following treatment in May of 1978, were extracted at regular intervals using aqueous acidic acetonitrile and the extracts analyzed using radiochemical and gas chromatographic techniques to monitor the herbicide breakdown. In addition, the polar solvent extracted soils were oxidatively combusted to determine bound residue formation. During the growing season there was a loss of extractable, and an increase in nonextractable, radioactivity so that by October only 15% of the applied 14C was solvent recoverable, while 37% was associated with the soil in a bound form. At all sampling dates the major soil transformation product was diclofop-acid, with 4-(2, 4-dichlorophenoxy)phenol as a minor metabolite. Minute traces of 4-(2, 4-dichlorophenoxy)phenetole and four other degradation products were also detected. © 1979, American Chemical Society. All rights reserved.