Effects of mefentrifluconazole on soil microorganisms, enzymes and earthworms in sandy soil and clay loam of peanut fields.

Our previous study indicated that mefentrifluconazole had a high efficacy in the control of peanut southern blight. However, the soil ecological risks of mefentrifluconazole in peanut fields were largely unknown. In this study, mefentrifluconazole was not readily degraded in soil that 0.1 mg/kg of mefentrifluconazole only degraded by 32.00 % and 35.00 % in sandy soil and clay loam after 60 days. It was also poorly vertically transported in soil that the relative displacement (R) values for mefentrifluconazole in both types of soil were 0.25. Moreover, substantial mefentrifluconazole was accumulated at a soil depth of 3-6 cm in both types. Consistent with residue dynamics, mefentrifluconazole had a long-term effect on soil microorganisms and enzymes. After 60 days, soil actinomycetes and bacteria recovered to control levels whereas fungi remained obviously lower than the control. It took at least 45 days for soil enzymes (urease, phosphatase and sucrase) to return to control levels. However, mefentrifluconazole exhibited low toxicity to earthworms. Only 14 days of exposure to 100 mg/kg of mefentrifluconazole resulted in significant weight loss in earthworms. In addition, earthworms showed obvious avoidance behavior toward mefentrifluconazole under natural leaching conditions. Above results suggested that mefentrifluconazole had prolonged effects on soil microorganisms and enzymes but showed low toxicity to earthworms.