The degradative characteristics of butachlor in the root-zone soils of different crops such as wheat, cotton,rice,maize and the bulk soils,and microbial population dynamics of culturable microorganisma capable of utilizing butachlor were investigated.A larger microbial population was measured in these crop rhizosphere soils compared to the non-rhizosphere soils.The increased population enhanced biodegradation of butachlor in the rhizosphere soils as compared to that in the non-rhizosphere soils.The degradative rates of butachlor in the wheat-,cotton-,rice-,or maize-rhizospheres were 1.63-2.34 times of those in nonrhizospheres,and the corresponding half-lives were shorten to be 42.2%-72.8% of those in the nonrhizoshere.The enhancemerrt in biodegradation was further strengthened by the inoculation of a bacterial strain mixture capable of utilizing butachlor as sole carbon and energy sources.Compared with those in the non-rhizosphere,the degradative rates in the rhizospheres increased up to 1.68-2.83 times after the inoculation.The microcosm in crop root-zone soil may be the optimal site for rapid degradation of residual pesticidesbutacholr.