Imazethapyr, HPLC-PDA, Oil, Terminal Residues, Soil, Soybean plant

Imazethapyr is widely used in pulses and leguminous crops including soybean for control of a broad spectrum of weed species. This has often resulted in carryover effects on several sensitive rotational crops. Therefore field studies were conducted for two consecutive years to evaluate residues of imazethapyr in the soil and the soybean crop produce. Imazethapyr was applied at 100 and 200 g/ha as post-emergence herbicide in soybean field. Residues of imazethapyr were found in the range of 0.011 to 0.063 μg/g in the straw following an application in soybean field at 100 to 200 g/ha in both the years. However in the soil and soybean oil, residues were found below 0.01 μg/g in both the years at two levels of application of imazethapyr. The overall residues were less in the soil as compared to the plant samples. Terminal residues of imazethapyr in soybean plant and soil were found below maximum residue level (MRL) limits. This study demonstrated enrichment of imazethapyr residues in soybean plants after repeated application. Based on this study a pre-harvest interval of 80-90 days for soybean crop after imazethapyr application is suggested.