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

Abstract

The degradation and leaching potential of the herbicide [14C]glufosinate-ammonium [the ammonium salt of DL-homoalanin-4-yl(methyl)phosphinic acid] in a northern Ontario forest environment were examined. The DT50 and maximum leaching depth were 4.3 days and 10 cm (humic layer), respectively. [14C]MPPA-S (3-methylphosphinylpropionic acid) and [14C]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.