Phosphorus supplying potential of European soils

摘要

The P supplying power of 26 European benchmark soils was investigated by means of desorption/sorption isotherms (Q/I plots) and by desorption graphs determined at increasing water-to-soil ratios (x). The desorption followed the equation y = c x~a where the parameters c and a stand for the P concentration in the soil solution at 100% moisture level and the P supplying power of soil, respectively. The parameter c correlated closely with the Al-bound P (r = 0.88***) and the P saturation of Al oxides (r= 0.92***) and with labile P (Q_0) (r = 0.83***) and the equilibrium P concentration (EPC_0) (r = 0.92***) derived from Q/I plot. In contrast, the parameter a did not correlate very closely with the P quantity parameters, the correlation coefficient withAl-bound P and the P saturation of Al oxide being -0.59** and -0.57**, respectively. Similarly, its correlation with the P buffering power of the sorption isotherm (EBC_0) remained rather weak (r = 0.47*), suggesting that the slope of the Q/I graph willchange at concentrations below the EPC_0 value. This means that the labile P (Q_0) derived from the Q/I plot at a fixed solution to soil ratio may underestimate the labile P reserves of the solid phase.