Residues and degradation dynamics of two herbicides in oat field soil

In order to study the residues and natural degradation characteristics of quinclorac and bensulfuron-methyl in oat (Avena sativa) field soil, we sprayed oat seedlings at the three- to four-leaf stage with the recommended dosage (225 g a.i.·hm^–2) and 1.5 times the recommended dosage (337.5 g a.i.·hm^–2) of quinclorac, and the recommended dosage (34 g a.i.·hm^–2) and 1.5 times the recommended dosage (51 g a.i.·hm^–2) of bensulfuron-methyl in April 2016. Residues were determined by high-performance liquid chromatography and the results showed that the degradation patterns of the two herbicides were consistent with a first order kinetic model. The half-lives of quinclorac and bensulfuron-methyl in oat field soil were 23.6～26.7 d and 17.9～20.1 d, respectively, and thus, it can be concluded that both pesticides are readily degradable. Under experimental conditions, the average recovery rates of quinclorac and bensulfuron-methyl at fortified levels of 0.05, 0.5, and 1.0 mg·kg^–1 were 85.63%～89.27% and 80.26%～91.61%, respectively, with relative standard deviations of 2.17%～6.33% and 3.28%～6.52%, respectively.