Degradation and Field Persistence of Imazethapyr

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Abstract
The volatilization, photolysis, microbial degradation, and field persistence of imazethapyr were studied using formulated and 14C-labeled imazethapyr. Volatilization losses from soil were less than 2%. Photodecomposition losses of up to 8% occurred from soil and up to 52% from a glass slide with no soil. Significantly greater photodecomposition occurred with chain-labeled than ring-labeled 14C-imazethapyr. The amount of 14CO2 evolution from soil treated with either ring- or chain-labeled 14C-imazethapyr was not significantly different. The total 14CO2 evolved from the soils ranged from 2.4 to 3.6% of the total 14C-imazethapyr applied to the soil. However, degradation of imazethapyr from the same soils, as determined by high-pressure liquid chromatography, indicated that 62 to 82% of the applied 14C-imazethapyr had been degraded. The degradation rate increased as soil moisture was increased from −100 to −33 kPa. Imazethapyr was more persistent in soil with the higher clay and organic matter content.