Although glyphosate is not recommended for direct application in soil, a significant amount may reach the soil during early-season or preplant applications (Haney et al., 2000). The soil half-life of glyphosate varies from few days to two or three months, and mostly, is smaller than one growing season; but, there are some reports of soil persistence for hundred and thousand days, and persistence of the phytotoxic activity for more than 19 weeks after the application (Heinonen-Tanski, 1989; Feng & Thompson, 1990; Weber, 1994).