Phosphorus (P) is limiting plant growth in many soils. Inorganic fertilisation has been massively used after world-war II in order to ensure high crop productivity by increasing soil P availability. However, the perspective of scarcity of the P-ore (phosphate rock) reserves and the negative side effects of P fertilization (e.g. eutrophication) urge to find an alternative. An option is to rely on naturally occurring interactions between roots and soil constituents in the rhizosphere. Such root-induced processes can promote P availability and thereby enhance or at least maintain crop productivity under reduced P fertilizer input. Different root-induced processes have been reported for their ability to increase P availability. The release of protons/hydroxyls in response to unbalanced uptake of cations and anions (e.g. Hinsinger, 1998) and the release of organic ligands (e.g. Ryan et al., 2001) are often considered as most important. Dissolution/precipitation and/or adsorption/desorption are the soil processes recognized for their control of P availability. The precipitation of P minerals has been largely reported in soils subjected to inorganic P fertilization, especially in calcareous soils, while adsorption/desorption would control P availability at low concentrations (e.g. Tunesi et al., 1999). However, little is known about the interactions occurring within the rhizosphere. Their promoting influence has been sparsely demonstrated and understood at a mechanistic level. A good understanding of both soil and root processes is required for that. Furthermore, the influence of global changes should be accounted for in order to anticipate their effects on P availability. Mechanistic modelling can be profitably used for those purposes, by enabling us to determine the nature of the controlling processes and mechanisms in rhizosphere, and by supplying a tool with reliable predictive capabilities. The present communication is aimed at reviewing recent works that proposed a mechanistic equilibrium model for simulating P availability in soil and rhizosphere (e.g. Devau et al., 2010). The predictive capacity of the model was demonstrated by modelling P availability as measured over a range of pH values and salt concentrations in soils exhibiting contrasted mineralogical composition. The major interest of the model for assessing the nature of the controlling processes and to determine the key mechanisms was also demonstrated through its applications to the rhizosphere of a crop species: durum wheat. A new root-mediated process was found to play a key role, the uptake of Ca ions, which markedly increased P availability in the rhizosphere as pH increased. This is an important finding as Ca is an essential element and a major nutrient for all plant species (White and Broadley, 2003). This communication will end up with application perspectives, such as to other important crop species as grain legumes, where the influence of low molecular weight organic ligands on P availability may be more important (e.g. Pearse et al., 2006).