Persistence and Leachability of Glufosinate-Ammonium in a Northern Ontario Terrestrial Environment

The degradation and leaching potential of the herbicide [ 14 C]glufosinate-ammonium [the ammonium salt of dl -homoalanin-4-yl(methyl)phosphinic 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), respectively. [ 14 C]MPPA-3 (3-methylphosphinylpropionic acid) and [ 14 C]MPAA-2 (2-methylphosphinylacetic acid), the two main metabolites of glufosinate-ammonium, also did not leach beyond 10 cm. At 32 days postapplication, approximately 10−20% of the parent and metabolites remained in the soil, but by the following season (day 295) residue levels had declined to near zero.