STUDY OF THE RELATION BETWEEN CARBOFURAN DEGRADATION AND MICROBIAL ORPHYSICOCHEMICAL CHARACTERISTICS OF SOME FRENCH SOILS

In France, corn rootworm (Agriotes sp.) is controlled by applying inse cticides such as carbofuran to the soil. In recent years, the failure of carbofuran to control this pest has been observed in the south-west area of France in continuous corn cropping. A soil survey was conduct ed in order to determine the main factors which could influence carbof uran degradation in various soils. Degradation estimates were based on measurement of the release of [C-14]carbon dioxide from [carbonyl-C-1 4]carbofuran. The enhanced degradation of carbofuran observed in labor atory conditions corresponded to the growth of micro-organisms able to use carbofuran as sole carbon and nitrogen source. The size of this m icrobial population and the rates of carbofuran degradation were highe r in the samples taken from plots with a history of carbofuran use tha n in samples from previously untreated plots. Abiological degradation was only observed in alkaline soil conditions. Statistical analyses sh owed that carbofuran-degrading activity was not related to any particu lar pedological characteristics.