One promising option for increasing soil P acquisition efficiency in agro-ecosystems is to make better use of plant diversity, and especially of the positive below-ground-interactions occurring between two intercropped species. Niche complementarity occurs when two species explore distinct soil volumes or access different pools of soil resources, e.g. inorganic and organic P. Facilitation occurs when roots of one species, or their rhizosphere microbial community, release P solubilising compounds such as protons/hydroxyls, carboxylates or phosphatases, thereby resulting in an increased availability of soil P, which ultimately benefits the intercropped species. This facilitative interactions will thus be promoted when the roots of the two intercropped species are closely intermingled. The need for close proximity roots may however be offset by mycorrhizal symbiosis, which might confer access to soil P resources at longer distances from roots. Better understanding these intimate rhizosphere processes shall help designing more P efficient intercropping systems for the future.