CROSS-ENHANCEMENT OF CARBOFURAN BIODEGRADATION IN SOIL SAMPLES PREVIOUSLY TREATED WITH CARBAMATE PESTICIDES

Laboratory incubation experiments were carried out to estimate the ris k of enhanced carbofuran biodegradation in soil following previous tre atments with Various carbamate compounds. Two soils with different sen sitivities to the enhanced degradation phenomenon were used. In the Mo ntardon soil, prior treatments with 15 N-methylcarbamates led to an en hanced rate of [C-14-carbonyl]carbofuran degradation and an increase i n the number of carbofuran-degrading microorganisms; prior treatment w ith formetanate and pirimicarb had no enhancing effect. In the Dijon s oil, prior treatment with six N-methylcarbamates, chlorpropham or aldi carb had no apparent effect on the subsequent rate of carbofuran degra dation and carbofuran-degrading microorganisms were not detected in an y of the prior treated samples. Chloroform fumigation of previously un treated and carbofuran treated soil showed that carbofuran degradation in the Montardon soil was mainly due to biological activity, whereas abiotic ao activity represented a third of the total degradation in Di jon soil. Treatment of both soils with cycloheximide and chloramphenic ol led to a decrease in the rate of carbofuran degradation, but strept omycin had a limited effect on the degradation rate. Further studies a re needed to characterize the carbofuran-degrading microorganisms whic h are present in soil after prior treatments with various N-methylcarb amate pesticides. (C) 1997 Elsevier Science Ltd.