Phosphorus-efficient faba bean (Vicia faba L.) genotypes enhance subsequent wheat crop growth in an acid and an alkaline soil

Faba bean (Vicia faba L.) is a carboxylate-exuding legume that enhances the phosphorus (P) nutrition of subsequently grown cereals. In an earlier study we found variation in soil P acquisition among 50 faba bean genotypes, but little is known about the rhizosphere processes that may contribute to P efficiency and whether these processes impact on the growth of subsequent cereal crops. In this study, we investigated rhizosphere dynamics (P fractions depleted, pH and carboxylate exudation) in three P-inefficient and five P-efficient faba bean genotypes in a glasshouse study on soils differing in P dynamics. The results suggest that P efficiency in the acidic soil was not driven by rhizosphere processes, consistent with earlier findings that root growth parameters contributed to P efficiency in this soil. In contrast, in the alkaline soil the most P-efficient genotypes had the highest malate exudation, which might enhance P solubilisation. For the first time, we showed a faba bean genotype-specific enhancement of growth and P uptake of subsequently grown wheat plants. This genotypic variation could be exploited to further increase the benefit of faba beans in rotation with wheat on P-limited soils.