Abstract
The degradation of bifenox, a diphenyl ether herbicide, methyl 5-(2, 4-dichlorophenoxy)-2-nitrobenzoate, in 3 arable soils collected from paddy fields and a subsoil from forest was studied under flooded and upland moisture conditions in the laboratory using 14C-bifenox labeled at the nitrophenyl ring. A great difference in the degradation pattern was observed between upland and flooded conditions, but the differences among the soils were small. In paddy soils under flooded conditions, bifenox was degraded rapidly and the half life period was within 4 days when the chemical was applied at 10ppm level. Three major degradation products, the free acid and the amino derivatives of the ester and free acid forms; and 5 minor products, the acetyl- and formyl-amino derivatives of the ester and free acid forms and the salicylic acid derivative were identified. In non-flooded paddy soils, bifenox was also degraded rapidly and the half life was about 6 days. The free acid of bifenox was the main degradation product and the amino derivatives were hardly detected. In the flooded sub-soil which contained a trace amount of organic matter, the degradation was similar to those in non-flooded paddy soils.
