The crop phosphorus nutrition management is a challenging issue in agriculture. The objective of this paper is to illustrate how the scientific progresses on the analysis of the biogeochemical P cycle in agrosystems make it possible to renew the P fertilisation recommendations and practices by identifying, quantifying and ranking the main processes that govern the soil-plant P transfer. Two new mechanistic-based indicators, the concentration of phosphate ion in soil solution and the transfer of diffusible phosphate ions at the solid-to-solution interface make it possible to assess the soil P availability. These new soil P availability indicators improve the diagnosis of crop P response by taking account mechanistically of the soil type effects on the definition of thresholds for P fertilisation management. The recent development of mechanistic models of biogeochemical of P cycle based on these two indicators of soil P availability allows to predict crop P uptake and the soil P availability dynamic on short and long term. Such models are useful to develop and test innovative P fertilisation strategies to improve P acquisition and utilisation efficiencies.