Effect of repeated application of 14C-carbaryl and of addition of glucose and cellulose to soil samples

Abstract

The behaviour of the insecticide carbaryl was studied in samples of Gley Humic and Red-Yellow Latosol soils by means of radiometric techniques. In the Red-Yellow LatosoI low in organic matter (0.36%) two carbon sources - glucose and cellulose, and a mixture of glucose plus cellulose were added. Glucose increased degradation of carbaryl, but at concentration of 0.1 mg/g of soil its effect was about the same as cellulose at concentration a hundred times higher (10 mg/g of soil). Addition of cellulose to soil samples containing glucose did not enhance the rate of degradation of carbaryl, indicating that microbial populations preferably use nutrient sources readily metabolized. Repeated applications of carbaryl in Gley Humic and Red-Yellow Latosol highly increased the rate of degradation, probably due to a rapid increase in the number of microorganisms by using the pesticide as substrate.