Fig. 1. Desorption isotherm of the soils of the pot experiment (Koopmans et al., 2004) describing the relationship between the P concentration measured in 1:10 (w/v) 0.01 M CaCl₂ extracts (vigorous shaking) and the total pool of sorbed P (open symbols). The Langmuir equation was fitted to the data. Furthermore, the total pool of sorbed P is plotted against the P concentration as a function of time measured in 1:10 (w/v) 0.01 M CaCl₂ extracts obtained under mild shaking conditions in the batch experiments (closed symbols).