Abstract: Gas chromatograph and bioassay were used to study biodegradation of acetochlor and its influence on the persistence against Echinochloa crusgalli in soil.The results showed that halflife of degradation of acetochlor was significantly shorter in unsterilized soil than that in sterilized soil under the same experimental conditions of concentrations,water content and temperature,when acetochlor was added to the soil with concentrations of 1.25,2.5 and 5.0 mg·kg^-1 respectively,which demonstrated that microorganisms could evidently degrade acetochlor in soil.The experiment on degradation of three main kinds of microorganism cultivated in liquid culture medium gave same results above.The bioassay’s result showed that the period of acetochlor persistence against Echinochloa crusgalli was shorter in unsterilized soil than that in sterilized soil,which indicated that existence of microorganism could accelerate the degradation of acetochlor and shorten remaining time of the herbicide in soil,consequently reduce its persistence against the weed.

Key words: Bita lake, Natural reserve, Ecotourism, Exploitation model