STUDIES ON THE PERSISTENCE OF DICLOSULAM IN SOYBEAN CROP

A three season field trial was conducted under West Bengal conditions during 2007–09 to evaluate the dissipation pattern of Diclosulam (84 WDG) in soybean at two application rates (26 and 52 g a.i./ha). The quantitative analysis of the herbicide residues was performed using HPLC with UV-VIS detector. The average recovery was found to be 90.67%, 88.67%, 88.33% and 89.33% for soybean cropped soil, soybean plant, soybean oil and de-oil cake, respectively. Following the first order kinetics, the herbicide dissipates in soybean cropped soil with half-life (T1/2) values ranging between 5.28 - 6.02 days, 7.52 - 8.36 days and 6.27 - 6.84 days in three consecutive seasons, irrespective of the doses. Diclosulam residues were below detectable level (BDL) in plant samples irrespective of the treatment doses and the days in all seasons. No residues were detected in untreated control samples of field soil and plant during the entire study period. Furthermore, soybean oil and its de-oil cake were also analyzed and Diclosulam residues were found well below the detectable limit, irrespective of the season and treatments. So it may be concluded from the study that Diclosulam will not pose any residual toxicity problem in soybean crop.