Persistence of metsulfuron-methyl in paddy field and detection of its residues in crop produce.

Among sulfonylurea herbicides, metsulfuron-methyl [methyl 2-(4-methoxy-6-methyl-1,3,5-triazine-2-ylcarbamoylsulfamoyl) benzoic acid] is widely used due to its selectivity against a wide range of weeds in cereal, pasture, and plantation crops. Use of persistent herbicides has increased risk of accumulation of residues in soil, groundwater, crop produce, food chain etc. Thus an experiment was conducted to see persistence of metsulfuron-methyl in paddy field under tropical conditions. Metsulfuron-methyl was applied at 2, 4, 5, and 8 a.i. g ha−1 rates after 25 days in transplanted rice as post emergence herbicide. Concentration of metsulfuron-methyl in soil at 30 days was found 0.008, 0.010, 0.011 and 0.016 μg g−1 at 2, 4, 5 and 8 g a.i. ha−1 application rates, respectively. However, residue level of metsulfuron-methyl in soil, rice grains and straw at harvest was found below 0.001 μg g−1.