Relating phosphorus quantity, intensity, and buffer capacity to phosphorus uptake

The short-term (25 days) phosphorus (P) uptake by maize has been reported to be most strongly correlated with measurements of P intensity in soil. Correlations of P uptake with bicarbonate-extractable P (a measure of the quantity factor) were improved when indices of P buffer capacity were included, but not to the extent obtained with the direct measure of P intensity. Thus, one might infer that measurements of the quantity factor and P buffer capacity were less satisfactory for describing P availability. It is now shown that this conclusion results entirely from the model fitted to the data. By using a multiplicative rather than additive model, it is shown that bicarbonate-extractable P in combination with measures of P buffer capacity can describe the P uptake data equally as well as a direct measurement of P intensity. Keywords: modelling, sorption. Australian Journal of Soil Research 36(3) 389 - 394 Full text doi:10.1071/S97107 © CSIRO 1998