Soil Degradation of Metazachlor in Agronomic and Vegetable Crop Fields

Metazachlor degradation in soil was studied in fields of spring barley, turnips, brussels sprouts, and leeks. Metazachlor in soil was transformed into 2-hydroxy-N-(2,6-dimethylphenyl)-N-(1H-pyrazol-1-yl methyl)-acetamide (compound 2), 2-chloro-N-(2,6-dimethylphenyl)-acetamide (compound 3), and 4,4'-methylenebis-(2,6-dimethylbenzenamine) (compound 4). Soil concentrations of compound 4 were always lower than 0.1 ppm. The half-life of metazachlor in the 0- to 10-cm soil layer was 1 to 3 mo. Metazachlor and compounds 2, 3, and 4 were not detected in the 10- to 20- and 20- to 30-cm soil layers. Metazachlor and metabolites (compounds) 2, 3, and 4 were not detected in barley grain or in the edible part of the vegetables. The sensitivity limit for these compounds was 0.02 ppm. Nomenclature: Metazachlor, 2-chloro-N-(2,6-dimethylphenyl)-N-(1H-pyrazol-1-ylmethyl)-acetamide; spring barley, Hordeum vulgare L., subsp. hexastichon 'Apex'; turnip, Brassica napus L., subsp. napus 'Leielander'; brussels sprouts, Brassica oleracea L., subsp. Gemmifera, 'Acropolis'; leeks, Allium porum L., subsp. 'Alberta'; lettuce, Lactuca sativa L., 'Hilde'; cabbage, Brassica oleracea L., subsp. Bullata, 'Savoy King'.