Soluble Phosphate in Soil and Uptake by Plants

Abstract

THE phosphate potential, defined by Schofield¹ as ½pCa + pH₂PO₄, has proved useful in describing the solubility of soil phosphate. However, Schofield went further and made out a case for the phosphate potential as one parameter of phosphate availability to plants, the other being the pool of labile phosphate measured by isotopic exchange. There is little doubt that plants may get insufficient phosphate because the concentration in the soil solution is too low, but it has not been shown whether this is due to concentration per se, or to a too-low potential (using Schofield's terminology)². The following experiment, which was carried out as part of a broader investigation, suggests an answer.