Four Common Pesticides On Soil Respiration And Its Effects Evaluation

For a long time, soil respiration strength was considered as one of the guide lines for soil microorganism activity or soil fertility. Following the increasing of pesticides' sorts and quantity, during the development and using of new pesticides, it has been one important criterion of evaluating pesticides' environment safety for many countries that researching the soil respiration strength under pesticide action.Now, it is not very clarity that the difference of pesticide pollutions and the soil respiration under pesticide action during the production of field and shed vegetables. It has more practical significance to carry such researching. This paper chose Carbendazim, Daconil, Imidacloprid and Methomyl as experiment objects, determined their influence to soil respiration of field, shed and school using obturate direct absorb method; discussed not only the variety of soil respiration under different pesticide's sorts, concentration and soil conditions but also the relationship between soil respiration and the variety of bacteria number in soil; confirmed the toxicity grade and dangerous index; provided an scientific basis for environment safety evaluation of pesticide's using.The experimental results indicate:Carbendazim can activate the soil respiration of field, shed and school; Daconil, Imidacloprid and Methomyl can active the soil respiration of field and shed, while have prohibitive effection to school soil.Under the experimental concentrations, the order of pesticide that can activate the soil respiration of field was: Daconil > Carbendazim > Methomyl > Imidacloprid.When the concentrate was 1mg/kg and 10mg/kg, the order of pesticides that can activate the soil respiration of shed respectively was: Carbendazim >Methomyl >Imidacloprid >Daconil, Carbendazim > Imidacloprid > Daconil > Methomyl; when the concentrate was 100mg/kg, the pesticides' order was Carbendazim > Methomyl > Imidacloprid except Daconil.The order of pesticides that restrain school soil's respiration respectively was: Methomyl > Imidacloprid > Daconil (1mg/kg); Daconil > Imidacloprid > Methomyl (10mg/kg); Methomyl > Daconil > Imidacloprid (100mg/kg).Carbendazim and Daconil have the almost same influence to soil bacteria's number and soil respiration; Imidacloprid and Methomyl can activate the growth of soil bacteria, the restrain to soil respiration maybe caused by inhibiting the growth of others bacteria groups.Through the toxicity evaluation, these 4 kinds of pesticides in common used were all to be the low toxicity or no toxicity grade to soil microorganisms.