PERSISTENCE AND LEACHABILITY OF GLUFOSINATE-AMMONIUM IN A NORTHERN ONTARIO TERRESTRIAL ENVIRONMENT

The degradation and leaching potential of the herbicide [C-14]glufosin ate-ammonium [the ammonium salt of DL-homoalanin-4-yl(methyl)phosphini c acid] in a northern Ontario forest environment were examined. The DT 50 and maximum leaching depth were 4.3 days and 10 cm (humic layer), r espectively. [C-14]MPPA-3 (3-methylphosphinylpropionic acid) and [C-14 ]MPAA-2 (2-methylphosphinylacetic acid), the two main metabolites of g lufosinate-ammonium, also did not leach beyond 10 cm. At 32 days posta pplication, approximately 10-20% of the parent and metabolites remaine d in the soil, but by the following season (day 295) residue levels ha d declined to near zero.