Microbial degradation of imazaquin and imazethapyr

Laboratory studies were conducted to investigate the processes of imazaquin and imazethapyr degradation in soil. Microbial degradation of C-14-imazaquin and C-14-imazethapyr was monitored by measuring (CO2)-C-14 evolution compared to nonsterile soil. (CO2)-C-14 evolution was greatest from carboxyl-labeled imazaquin and imazethapyr compared to ring-labeled imazaquin and imazethapyr. A corn root bioassay indicated nearly complete loss of herbicidal activity in nonsterile soil after 5 mo, but herbicide activity was reduced only 14% in sterile soil. (CO2)-C-14 evolution more than doubled when soil temperature increased from 15 to 30 C. Total CO2 production responded similarly. Degradation of imazaquin and imazethapyr increased as soil moisture increased from 15% (-2.4 MPa) to 75% of field capacity (-0.03 MPa).