Thus, the higher amount of the herbicide itself or its metabolites in the soil, the lesser metabolism would be expected. Feng & Thompson (1990) had also detected rapid initial degradation, but detected glyphosate and AMPA residues up to 360 days after the herbicide application. Araújo et al. (2003) detected higher amounts of AMPA in glyphosate agriculturally treated soils than in soils treated only one time, which means that AMPA may be accumulated in soil and is more persistent than glyphosate. The decreasing tendency of the mineralized amounts, as well as the increasing half-lives values calculated from the 14CO2 amounts with the increasing number of treatments, mean that repeated applications of glyphosate may result in gradual difficulty for soil metabolism of the total molecule.