Degradation Dynamics of an Acetanilide Herbicide — Alachlor in Groundnut

Results of a field experiment conducted at the Jaguli Instructional Farm, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal during the year 2011–2012 to study the degradation dynamics of an acetanilide herbicide alachlor on groundnut ecosystem are reported. Alachlor (50% EC) was applied to the cropped soil @ 2500 and 5000 g a.i. ha⁻¹at 39 days after seed sowing and plant and soil samples were monitored on 0 (2h after spraying), 1, 3, 5, 7, 10 and 15 days after application of the herbicide and also at harvest. The initial deposit on groundnut leaf varied from 0.36 to 0.47 at the recommended and 0.85 to 0.89 μg g⁻¹ at double the recommended dose whereas in groundnut field soil, the initial deposits were 1.08 to 1.15 and 2.57 to 2.65 μg g⁻¹ for the recommended and double the recommended doses respectively. The residues in leaf were below the limit of quantification of 0.01 μg g⁻¹ at 15^th day after the application whereas these persisted up to 15^th day in soil samples irrespective of dose. No residue of alachlor was observed both in harvested groundnut crop and soil samples at harvest. The half-life values were in the range 5.28 to 7.0 days irrespective of the dose and the substrate.