Degradation of buprofezin in flooded and upland soils under laboratory conditions

[Phenyl ring-U-14C] buprofezin, 2-tert-butylimino-3-isopropyl-5-phenyl-perhydro-1, 3, 5-thiadiazin-4-one, gradually decomposed in soils under flooded and upland conditions, with the half lives of 104 and 80 days, respectively. After 150 days, five degradation products were identified by thin-layer cochromatography: 2-tert-butylimino-5-(4-hydroxyphenyl)-3-isopropyl-perhydro-1, 3, 5-thiadiadin-4-one, 3-isopropyl-5-phenyl-perhydro-1, 3, 5-thiadiazin-2, 4-dione, 1-tert-butyl-3-isopropyl-5-phenyl-biuret, 1-isopropyl-3-phenylurea and phenylurea. As minor products, 2-tert-butylimino-5-phenyl-perhydro-1, 3, 5-thiadiazin-4-one or buprofezin sulfoxide were found in the flooded or the upland soil. [14C]Carbon dioxide and bound 14C residue accounted for 23-24% and 13-21% of the applied radioactivity, respectively. The degradation of buprofezin remarkably delayed in sterile soils. Since neither formation of 14CO2 nor ring hydroxylation was observed in the sterile soils, buprofezin seems to have undergone complete mineralization in the soils under both flooded and upland conditions through biological transformation by soil microorganisms.