Efficacy and fate of glyphosate on Swedish railway embankments

The herbicide glyphosate, N-(phosphonomethyl)glycine, as Spectra (240 g AI litre-1 SL; Monsanto Europe AB), RoundUp (360 g AI litre-1 SL; Monsanto) and RoundUp Bio (360 g AI litre-1 SL; Monsanto), have been used for weed control on Swedish railway embankments since 1986. This article summarizes results from studies of the weed effect and behaviour of glyphosate for the period 1984-2003. Studies on a railway embankment with a range of application rates showed excellent weed control at 5 litre ha-1 of RoundUp Bio. The appearance of glyphosate and its metabolite AMPA [(aminomethyl)phosphonic acid] in the embankment, eg mobility and persistence, was also studied. Mobility was low in most cases, the main proportion of both glyphosate and AMPA being found in the upper 30-cm layer although minor amounts penetrated to lower depths. The 50% disappearance time of glyphosate was generally