Journal of Food Legumes

Imazethapyr is widely used in soybean and very recently recommended for control of wide spectrum of weed species in rainy season pulse crops. Pot and field studies were conducted to evaluate dissipation pattern and the residues of imazethapyr in the soil, mungbean straw and grain continuously for three consecutive years of 2014–2017. Imazethapyr was applied at its recommended dose of 100 g/ha, as a postemergence (21 days after sowing) to control weeds in rainy season mungbean. In field experiments, imazethapyr residues were found far below to its prescribed MRL value(0.1mg/g). The residue of herbicidein field soil was found 0.00043, 0.00038, 0.00027, 0.00021, 0.00016 and 0.00012 mg/g of soil, respectively at intervals of 2hrs, 5^th, 15^th, 25^th, 35^th, and 45^th days of herbicidespray whereas, inpotsranged between 0.0082 to 0.0042mg/g of soil, respectively between the time period of 2 hours to 70 days of herbicide application. The plant and grain samples were foundal most free of residue. The degradation of imazethapyrin soil and in pot studies was foundto operate as per firstorder kinetic equation viz., [dMi/Dt=K (M_á-M_i)]. Based on residue data obtained in both of the experiments i e field and pots, it was observed that inlight textured soil, 50%of the herbicide got dissipated within a period of 26 days of herbicide spray (calculated T_1/2 =26 days, average K=2.74X10⁻²), whereas, in pots (soil contain comparatively more clay and organic carbon), the 50% concentration of the herbicide was found to persist up to a period of 82 days (calculated T_1/2 =82 days, k=8.59X10⁻³) and 90% herbicide got decayed within 268 days. Based on dissipation studies and calculated average K=2.74X10⁻², the effectiveperiod(T_eff.)infield wascalculatedas15-20days, which suggest imazethapyr can only provide protection to crop against weed up to a maximum period of 15–20 days.