The Study On Aspergillus Lfavus Degrading Soybean Herbicides

As a kind of sulfonylurea herbicide, chlorimuron-ethyl has been widely used in thefarmland because of its broad spectrum, high activitity, low dosage, and low cost. However,the long term effective residues in soil seriously damage crop production. Therefore, it isparticularly important to recover and decontaminate the soil. It has proved that using themicroorganisms to degrade herbicide residue in soil was a major efficient way.A strain was isolated in enriched culture from soil that had been contaminated withchlorimuron-ethyl for a long time. The conditions of degrading chlorimuron-ethyl for the trainin pot with soil in the laboratory were determined. The degrading efficiency of the train wastested with planting rapeseed seedlings.A strain Q6highly effective degrading chlorimuron-ethyl was identified as Aspergillusflavus. The degradation rate of chlorimuron-ethyl was highly related with the growthconditions of strain. The optimal conditions of carbon content, pH, temperature, ventilation,inoculation rate, the chlorimuron-ethyl concentration and the time were0.5%,6.5,35℃80mL/250mL,5%, and10mg/L respectively. The degradation rate reached to84.27%underthe optimal conditions in4days. Compare with the treatment inoculated with the Q6, the rateof degrading chlorimuron-ethyl was higher than the non-inoculated treatment. The rate insterile soil was lower than the none-sterilized. The optimal degradation conditions includingpH, temperature, the edaphic humidity, and inoculation rate were6.5,35℃,60%,10%respectively. The degrading rate was not obviousy related to concentration ofchlorimuron-ethyl though the degrading rate was relatively higher at10μg/kg ofchlorimuron-ethyl. The degradation rate after the18d became slower. As the degradation timeincreased, the accumulation degradation rate increased, and the accumulation degradation ratereached to90.88%on45d. Comparing with control，the height and fresh weight of rapeseedseedlings in the soil containing chlorimuron-ethyl was obviously increased (p <0.05) withtreatment of strain Q6and the seedling height reached to that without chlorimuron-ethyl (p<0.05).Overall, strain Q6degrading rate to chlorimuron-ethyl was affected with its growthenvironment. The degradation rate was higher in early period, slower in later period. Q6could effectively degrade chlorimuron-ethyl in soil and improve the germination rate, plant heightand fresh weight of rapeseed seedling.