Table 2.

Reported levels of residual top soil concentrations of glyphosate and AMPA and the respective plant-available fractions of counterions in soils (data compiled from various references: Franz et al. 1997 (16 soils), Aparicio et al. 2013 (32 soils), Peruzzo et al. 2008, Afzal 2017 (13 soils), Laitinen et al. 2009 (different soil depths)

Component	Soil concentration (μmol/kg dry weight)
Glyphosate
High contamination level	10–30
Low contamination level	0–5
Glyphosate + AMPA
High contamination level	20–40
Low contamination level	0.5–7
Plant-available counterions
Zn	40–80
Mn	500–2000
Fe	900–1800
Mg	4000–150,000
Ca	25,000–250,000