Butachlor, Dissipation, Half life, Residues, Rice

A field experiment was conducted in an Alfisol to study the degradation of butachlor and its residues in paddy grain during Rabi and Kharif seasons of 2007-08 at College Farm, College of Agriculture, Rajendranagar. Butachlor dissipated with half life varying from 12.5 to 21.5 days when applied at the rate of 1.0 and 2.0 kg/ha under with and without organic manures conditions. The observed half life values were lower for lower dose of applied herbicide as compared to higher dose and the field half life of butachlor was more under without organic manures as compared to organic manures applied plots. Residues of butachlor in field soil were analysed by using gas chromatograph and 100% dissipation of butachlor was observed at the time of harvest of crop.  Very low levels of residues were detected in rice grain below the maximum residue limit of 0.5 mg/kg. Therefore, application of butachlor in paddy for weed management can be considered safe from the point of consumption of grain.