Sorption/desorption equilibria control the concentrations of P in the soil solution and thereby both its chemical and bioavailability. Apart from the equilibrium phosphorus dynamic, which has been used to determine buffer power and the equilibrium concentration for the studied soils at Cruden Bay, Balmedie, Blairton Wood and Newburgh, the buffer power and equilibrium concentration were affected by the fertiliser incubation period. The differences in PBP and EPC were observed between the soils with high constituents of organic matter and clay in their texture and those which had sandy and sandy loam textures. The glasshouse study was conducted to evaluate the relationship between soil phosphorus availability and two contrasting spring barley genotypes. Both genotypes: Tocada and Natasha responded to added phosphate fertiliser in all treatments. The vegetative growth variations among the genotypes did not appear at different phosphorus levels for most of the studied soils. However, the study has revealed the differences in the root system of Tocada and Natasha in low phosphorus conditions. Tocada was prone to forming large root biomass when compared to Natasha in insufficient phosphorus conditions. Natasha behaved in the opposite way in sufficient phosphorus conditions. The findings of this study confirm that phosphorus use efficiency and root architecture of these genotypes are correlated with each other to exploit more available phosphorus in the rhizosphere. Both Agronomic and physiology Phosphorus use efficiency have been tested. Although the difference in agronomic phosphorus use efficiency among the genotypes was not recorded, some different observations in physiological phosphorus use efficiency among the genotypes were noticeable in some cases.