Mobility and Persistence of Metolachlor and Aldicarb in Field Lysimeters
- B. T. Bowman *
The mobility and persistence of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], a herbicide, and aldicarb [2-methyl-2-(methylthio)propanaldehyde O-(methylcarbamoyl) oxime], an insecticide, were studied using field lysimeters containing 15 cm (diam.) by 70 cm (length) cores of Plainfield sand (mixed, mesic Typic Udipsamments). One-half of the cores received only rainfall, while the remainder received rainfall plus simulated 50.8-mm rainfalls on the second and eighth days after treatment, followed by simulated irrigation for the duration of the study. Metolachlor exhibited limited mobility, except in the supplementary watering treatment, in which there was rapid transport of some herbicide 40 cm down the core, with accompanying traces in the effluent. Metolachlor half-life was in the 3- to 4-wk range. Aldicarb rapidly converted to its sulfoxide [2-methyl-2-(methylsulfinyl)propanal O-(methylamino)carbonyl oxime] and sulfone [2-methyl-2-(methylsulfonyl)propanal O-(methylamino)carbonyl oxime] (50% in 3–5 d). Under normal rainfall, about 9% of the applied aldicarb leached out of the soil cores as sulfoxide or sulfone. In cores receiving supplementary watering, up to 64% of applied aldicarb appeared in the effluent principally as sulfoxide or sulfone.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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