Metabolism of carbaryl and carbofuran in soil planted to rice

Abstract

In greenhouse experiments carbaryl and carbofuran disappeared more rapidly from a soil planted to rice than from an unplanted soil under both flooded and non-flooded (60% water-holding capacity) conditions. The rate of degradation was little affected by the moisture regime. The degradation of both carbamate insecticides proceeded essentially by hydrolysis. Further degradation of the hydrolysis products, 1-naphthol from carbaryl and 2,3-dihydro-2,2-dimethylbenzofuran-7-ol from carbofuran was slow in both planted and unplanted systems. A significant portion (20-38%) of the ring ¹⁴C in carbaryl and carbofuran accumulated in the soil as the respective hydrolysis products + soil-bound residues. Evolution of ¹⁴CO₂ from the ¹⁴C (from both side chain and ring labels) in carbaryl and carbofuran was negligible even in soil planted to rice.