Rice plant uptake of fresh and aged residues of carbofuran from soil

The uptake of carbofuran (2,3-dihydro-2, 2-dimethyl-7-benzofuranyl-N-methylcarbamate) residues, fresh and aged, by rice plants was investigated by growing them for 42 days in soils containing freshly treated (T-1), 3-month-aged (T-2), and 6-month-aged residues (T-3). Mineralization of [14C]carbofuran in soil to 14CO2 during the period was 4.4 (T-1), 11.0 (T-2), and 15.7% (T-3). 3-Ketocarbofuran phenol (2,3-dihydro-2,2-dimethyl-3-oxo-7-benzofuranol) was the major metabolite of the aged soils, whereas 3-hydroxycarbofuran 2,3-dihydro-2,2-dimethyl-3-hydroxy-7-benzofuranyl N-methylcarbamate) was the major metabolite in the shoots. The 14C radioactivity present in rice plant tissues after harvest was 26.8 (T-1), 21.4 (T-2), and 10.3% (T-3). The nonextractable soil-bound residues were 8.3 (T-1), 37.9 (T-2), and 54.6% (T-3) of the originally applied carbofuran. The small upward translocation of 14C radioactivity in T-3 suggests that the major metabolite, 3-ketocarbofuran phenol, is conjugated in roots and the low recovery in T-1 indicates the loss of carbofuran from the shoots