Effects of mefenacet and pretilachlor applications on phospholipid fatty acid profiles of soil microbial communities in rice paddy soil

The effects of herbicide (mefenacet and pretilachlor) applications on soil microbial communities in rice paddy soil were investigated in a laboratory study using phospholipid fatty acid (PLFA) profiles. Soils with or without herbicide application were incubated separately under oxidative or reductive conditions for 30 d. Half-life (DT50) of mefenacet was 14 d under oxidative conditions and 9.8 d under reductive conditions. DT50 of pretilachlor was 17 d under oxidative conditions and 8.8 d under reductive conditions. PLFA contents did not seem to be affected by the residual levels of herbicides. The composition of PLFAs under in both the oxidative and reductive conditions fluctuated during the incubation period. However, the effects of applications of herbicides (mefenacet and pretilachlor) under oxidative and reductive conditions in rice paddy soil did not affect appreciably the soil microbial biomass and the structure of the soil microbial communities, as determined by PLFA profiles. Fluctuations in the composition of PLFAs during the incubation period were rather conspicuous.