The influence of phorate residue on soil microbial activities

Influence of phorate on the quantities of soil microbes,microbial biomass C,biomass N and enzyme activities under the laboratory control condition was studied.Phorate was added to soil at dosages of 2,8,20 mg/kg,respectively.The results showed that after the application of phorate,the number of fungi and actinomyces decreased slightly,but then recovered quickly to the levels of CK.Bacteria community was inhibited significantly and the inhibiting effect was more obvious with the concentration of the phorate increased.The average inhibiting rate of bacteria by three concentrations of phorate were 17.5% ,35.9% and 48.5% ,respectively.Soil microbial biomass C and N decreased significantly with the increasing of concentration of the phorate.Compared with CK,soil microbial biomass C and N decreased in average by 20.8% ,34.8% ,39.2% and 19.1% ,28.2% ,36.1% ,respectively after treated by 2,8,20 mg/kg phorate.The activities of the soil sucrase,soil protease,and alkaline phosphatase in soils treated with the same concentration of phorate were all inhibited remarkably,the average inhibiting rates were 28.0% ,23.6% and 9.8% ;12.1% ,13.6% and 23.8% ;13.4% ,16.1% and 26.3% ,respectively.Compared with CK,the soil SMB-C/SOC decreased by 13.1% ,28.6% and 25.0% ,respectively,when phorate was added to soil at dosages of 2,8,20 mg/kg 30 days later.Conclusion:The microbial community structure changed and the microbial activity reduced when phorate was added to soil.