From Wikipedia
The
half-life of glyphosate in soil ranges between 2 and 197 days; a typical field half-life of 47 days has been suggested. Soil and climate conditions affect glyphosate's persistence in soil. The median half-life of glyphosate in water varies from a few to 91 days.
[55] At a site in Texas, half-life was as little as three days. A site in Iowa had a half-life of 141.9 days.
[87] The glyphosate metabolite AMPA has been found in Swedish forest soils up to two years after a glyphosate application. In this case, the persistence of AMPA was attributed to the soil being frozen for most of the year.
[88] Glyphosate adsorption to soil, and later release from soil, varies depending on the kind of soil.
[89][90] Glyphosate is generally less persistent in water than in soil, with 12- to 60-day persistence observed in Canadian ponds, although persistence of over a year has been recorded in the sediments of American ponds.
[86] The half-life of glyphosate in water is between 12 days and 10 weeks.
[91]