Root-induced pH changes enhance the availability of soil phosphorus in the rhizosphere of intercropped cereal-legume: the other side of the coin

International audienceAims and Background Facilitation of phosphorus (P) uptake can occur in cereal-legume intercropping through rhizosphere interactions. In alkaline and neutral soils legumes are assumed to increase inorganic P availability and facilitate cereal P uptake by rhizosphere acidification due to N2-fixation. Methods Phosphorus uptake and changes in inorganic P availability and pH in the rhizosphere of intercropped species were investigated in a greenhouse pot experiment with durum wheat (Triticum turgidum durum) and chickpea (Cicer arietinum) either monocropped or intercropped. We used two neutral soils from a P-fertilizer long term field trial exhibiting either low (-P) or high (+P) P availability. Results Phosphorus uptake of both species was increased in +P but intercropping had no significant effect. In - P, intercropping increased wheat’s rhizosphere pH and inorganic P availability in the rhizosphere of both species. In +P similar intercropping effect was only observed for wheat. Low rates of N2-fixation may explain why no acidification was observed in chickpea’s rhizosphere. Conclusion Whereas the increase in inorganic P availability in intercropping was assumed to occur as a consequence of root-induced acidification by the legume, we suggest that root-induced alkalization can also be involved, thereby resulting in facilitation of the legume by the cereal