Several phosphate solubility and availability parameters were obtained for calcareous soil samples fertilized with superphosphate, partially acidulated phosphate rock and a mixture of the two. Plant response to the fertilizer application was studied in a greenhouse experiment. The ionic product of calcium carbonate phosphate [Ca3(HCO3)3PO4] correlated best with the plant response parameters. The correlations of the plant response parameters with the other solubility parameters (CaPO4, H2PO4or HPO4potentials) were higher than that obtained with conventionally determined available soil phosphorus (P).