Mere chemical processes are unable to break the C–P
bonds of the glyphosate molecule. Instead, free glyphosate
in soil is degraded to CO2 and NH3 by microbes, mainly
bacteria such as Pseudomonas [3], whose activity is affected,
for example, by temperature, acidity and moisture [20].
Soil microbes in general are poorly known, and even less is
known of their variability, growth rate and function in
northern ecosystems. The microbial species [23] and even
strains [24] differ in their efficiency and mode of degrading
glyphosate. Still it seems clear that in northern climatic
conditions strong seasonality limits the time period of peak
activity of glyphosate degradation to summer months.
Furthermore, there is pressure to give glyphosate treatments
late in season to accelerate ripening and kill the
weeds before seed set. Thus, the half-life time of glyphosate
may be much longer in northern ecosystems than generally
presumed [3,22].