Dissipation of herbicides chlorsulfuron and imazosulfuron in the soil and the effects on the soil bacterial community.

ABSTRACT

Dissipation of Sulfonylurea herbicides has rarely been studied due to their low application dosage. In this study, two herbicides, chlorsulfuron and imazosulfuron, were applied to both Podu (Pu) and Wolylin (Wl) soils at concentrations of 10 mg kg(-1) or 50 mg kg(-1) with soils at filled water holding capacity and incubation under 30 degrees C. Changes in the soil bacterial community were examined with denaturing gradient gel electrophoresis (DGGE), whereas the residue of the herbicides was measured by high performance liquid chromatography (HPLC). The dissipation mechanisms of the two herbicides were both chemical and biological. The half-life of chlorsulfuron is 6.8-28.4 days and that of imazosulfuron is 6.4-14.6 days. These both dissipate faster in a more acidic soil. A higher dosage inhibited 48 % of the dissipation of the chlorsulfuron in Wl soil. However, larger differences were not observed in other treatments. The half-lives of both herbicides for 10 mg kg(-1) or 50 mg kg(-1) concentrations were less than one month. The microbial community was changed after the chlorsulfuron and imazosulfuron were spiked. Two sulfonylurea herbicides changed the soil bacterial composition after they were amended, and the change was larger with imazosulfuron under 50 mg kg(-1) of concentration.