Over the entire region of investigation (120 ha), will be taken in soil samples at different depths. The sampling will be done after an exploratory sampling site. Explore during this recovery phase will examine how deep the P saturation front is located. We have chosen to work on perceelsniveaut because this is also the level at which fertilization occurred. We expect that the variability between plots in P availability will mainly caused by the degree and frequency of contamination (in terms of land use), as well as the depth of the groundwater