In a study with Guelp loam, the half-life of metribuzin was about 3 months. In four Manitoba soils under dry conditions at 15 C, some nonbiological degradation of metribuzin occurred. Field soil samples awaiting analysis underwent degradation. 3,5-Diketo and deaminated diketo also degraded under storage conditions. Metribuzin and deaminated diketo were observed.
Microbial degradation is the primary fate process of metribuzin in soil .
Activity of soil microorganisms, higher temperatures and aerobic conditions increase the rate of metribuzin biodegradation . The half-life of metribuzin in soil at normal use rates is about 30 to 60 days during the growing season . For example, half-lives of 3.08 and 2.04 weeks were determined in Plainfield sand after rainfall and supplementary water treatments . Activity of soil microorganisms, higher temperatures and aerobic conditions increase the rate of metribuzin biodegradation . Based on a reported vapor pressure of less than 1X10-5 mm Hg at 20 deg C , metribuzin should exist in the vapor and particulate phases in the ambient atmosphere .