Clomazone volatilization under varying environmental conditions

Velvetleaf (Abutilon theophrasti Medik.) was used as a bioindicator to examine factors (temperature, soil moisture, soil incorporation) which might influence clomazone {2-[(2-chlorophenyl)methyl] -4,4-dimethyl-3-isoxazolidinone} volatilization. Young plants were periodically exposed to atmosphere inside boxes containing clomazone-treated soil. Exposed plants were returned to the greenhouse for 5 to 7 d, and new leaves were assayed for chlorophyll. Maximum chlorophyll inhibition occurred in velvetleaf exposed during the first 2 wk after clomazone application. Reductions in degree of bleaching were first observed in plants exposed in the treatments with lower soil moisture (2% moisture at 19 days after clomazone treatment, DAT; 9% at 42 DAT). The least amount of clomazone was measured in soils incubated in the 35 °C treatment, indicating elevated temperatures enhanced volatilization, and may have contributed to the increased chlorophyll content observed observed earlier than other temperatures. The effect of herbicide incorporation was not conclusive.