DEGRADATION OF FENITROTHION IN FOREST SOIL AND EFFECTS ON FOREST SOIL MICROBES

Two forest soils were treated with [ring-14C] fenitrothion (7.4 ppm in wet soil) and held in a dark growth chamber at 30 °C for 50 days. Periodic sampling and analysis revealed that 50% degradation of fenitrothion occurred in 3 days. Furthermore, the transient formation of 3-methyl-4-nitrophenol (MNP) and the formation of C02and soil-bound radiocarbon as terminal products were also established. Results were similar in both forest soils. After 50 days of incubation of the soils, the originally applied 14C was accounted for as fenitrothion (3-6%), MNP (5-7%), 3-methyl-4-nitroanisole (4%), C02(35%), and soil-bound radiocarbon (48-50%). The bound radiocarbon was associated mainly with humic acid and fulvic acid fractions. Minimal degradation occurred in sterilized soils, suggesting microbial activity was responsible for the observed degradation of fenitrothion. Furthermore, the soil microflora were not qualitatively affected by fenitrothion. From these studies fenitrothion can be regarded as a readily degradable insecticide in forest soil which is not deleterious to the forest soil microflora. © 1979, American Chemical Society. All rights reserved.