The Dissipation Kinetics Of Mvclobutanil In Tea Orchard Soils And Its Impact On Soil Microbial Activities

According to new MRLs set byEUregulatory agencies,the export of Chinese teais impacted negatively. Pesticide residues in teas are contributed mainly from directspraying and the secondary pollution from polluted soils.As a triazole fungicide, myclobutanil is a sterol demethylation inhibitor. It is a broad-spectrum systemic fungicide used to control many plant diseases. Particularly, it is effective on powdery mildews and rusts in a variety of cereal, fruit and vegetables.Theexperiment focuses on the dissipation kinetics of myclobutanil in three different aged tea orchard soils, forest soil and wasteland soil, to identify the dissipation kinetics and half-lives of myclobutanil and discuss the influent factors.Myclobutanil was applied to2-3a&50a tea soils at three rates:0.1μg/g;1μg/g;10μg/g to ascertain the impact of myclobutanil on soil microbial activities. The main results are as follows:(1)Myclobutanil dissipation was mediated by the microorganisms, and neglecteddissipation was observed in steriled soils. Over10day incubation, in nonsterile soils,9.04-36.92%of myclobutanil was lost.The soil moisture content affected the dissipation rates of myclobutanil.In non-flooded soils (60%), myclobutanil was dissipated at much faster rates than flooded soils (125%). The higher dissipation of myclobutanil under non-flooded soils can be attributed to aerobiosis and associated microbial activity. Dissipation rate was significantly increased at40℃compared to those at4℃and25℃for all five soils (p<0.05) and highest in50a teaorchard soil under all incubation conditions except for sterilized treatments.(2) High concentration of myclubutanil had negative effect on soil quality indicators, including microbial biamass carbon (MBC), dehydrogenase (DEH) activity and basal respiration. Myclubutanil at the level of0.1μg/g,DEH activity and basal respiration was stimulated significantly, while in1&10μg/g treated soils, soil microbial activities were inhibited, and50a tea orchard soil’s resistance ability was stronger than2-3a. The microbial activities were more inhibited in10μg/g treated soils than1μg/g. After10day incubation, MBC and basal respiration decreased significantly.The DEH activities were similar in two soils, and in5th day, the maximum inhibition of DEH activities could be observed.