Residues of glyphosate and its metabolite AMPA in field pea, barley and flax seed following preharvest applications

Cessna, A. J., Darwent, A. L., Townley-Smith, L., Harker, K. N. and Kirkland, K. J. 2002. Residues of glyphosate and its metabolite AMPA in field pea, barley and flax seed following preharvest applications. Can. J. Plant Sci. 82: 485-489. Maximum residue levels have been established by Health Canada for seed of several crops treated with preharvest applications of glyphosate, a common practice on the Canadian prairies. Residues of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) were determined at crop maturity in flax seed at one site in western Canada and in the seed and straw of field pea and barley at another site following preharvest applications of the herbicide. Glyphosate was applied at rates of 0.45, 0.9 and 1.7 kg ha(-1) to each crop in early August to mid-September at four stages of crop development. In all crops, mean residues of glyphosate and AMPA increased with increasing application rate of glyphosate and decreased when the herbicide was applied at later stages of crop development.