Phosphorus (P) occurs at low concentrations in soils because of the numerous processes responsible for P sorption or immobilisation. Soil P is also characterised by its restricted mobility, and thus the most limiting step of P acquisition is not its absorption by plant roots, but rather the many processes that determine the fate of soil P in the rhizosphere. This chapter describes these various processes, including those directly mediated by plants (which vary considerably with plant species), and those related to soil microbial and microfaunal activities. In order to overcome the restricted mobility of soil P, plants have evolved several features aimed at increasing the rhizosphere volume by increasing the absorptive surfaces, notably root elongation and branching. The formation of root hairs and mycorrhizas is also triggered by interactions with plant growth promoting microorganisms. Plants have also evolved strategies aimed at increasing soil P concentrations via the mobilisation of inorganic and organic pools of soil P. These imply changes in pH, and the release of P-mobilising compounds such as carboxylates and phosphatases, that are exuded by the roots themselves or by rhizosphere microorganisms. Finally, the soil microfauna (especially the predators of bacteria and fungi) play an important role in the cycling of soil P in the rhizosphere that deserves further consideration.