Field studies indicated thiazopyr at 220 g ha−1 injured soybeans planted in no-till, and 340 g ha−1 injured soybean in 1 of 2 yr planted into tilled soil. Thiazopyr half-lives in three field studies ranged from 12 to 14 d, indicating minimal potential for carryover injury to sensitive rotational crops. Thiazopyr dissipation under controlled conditions was slower than under field conditions. Half-lives at 15 and 30 C were 133 and 43 d, respectively. This indicates that microbial degradation is an important mechanism in thiazopyr dissipation, but that other loss mechanisms also play a role. A method using methanol extraction of moist soil samples followed by gas chromatography using a nitrogen-phosphorous detector had > 90% recovery of thiazopyr.
