Transformation of metamitron in a sandy clay loam soil

The degradation of metamitron, a sugar beet herbicide, in soil was studied in laboratory conditions and in field lysimeters under different irrigation water volumes. An identification of degradation compounds was also attempt ed. Laboratory degradation followed a first-order kinetics with a half-life of 18.2 days while lysimeter dissipation was consistently rapid with a hal f-life ranging from 4.4 to 8.0 days under the different irrigation conditio ns. A degradation compound appeared as early as the first few days in both laboratory and lysimeter samples and was identified as 4-(dimethylimino)-3- methyl-6-phenyl-1,2,4-triazin-5(4H)-one by GC/MS and NMR spectra. ((C) Inra /Elsevier, Paris.).