Mycorrhizal networks promote interspecific facilitation in P uptake by a maize/faba bean mixture

Background and aims: Interspecific belowground interactions can facilitate phosphorus (P) uptake in cereal/legume intercropping. However, the role of mycorrhizal symbioses and their interaction with root exudates in the improved P uptake in intercropping is not clear. This study aimed to investigate how the interaction between roots, root exudates and mycorrhizal fungal hyphae affected P uptake by maize mixed with faba bean. Methods: Microcosms with two compartments and low-P soil were used, separated by solid plastic sheet, 0.45 μm nylon mesh, 30 μm nylon mesh, or no barrier. One compartment contained maize, and the other contained maize or faba bean. Plant biomass, P content, root exudates, mycorrhizal colonization rate and root morphological parameters were determined. The contribution of root proximity, root exudates and mycorrhizal networks to plant biomass and P uptake were calculated. Results: For maize/faba bean mixture, biomass and shoot P content of maize with no barrier and 30 μm mesh were similar and higher than with solid plastic sheet and 0.45 μm mesh, indicating the beneficial effect of mycorrhizal networks. There was no difference in biomass and P content among different root separation treatments for monocultured maize. Rhizosphere pH and acid phosphatase activity of maize were different among barrier treatments regardless of mixture or monoculture. Conclusion: The mycorrhizal networks among the interspecific belowground interactions played a major role in promoting the growth and P uptake of mixed maize in a maize/faba bean mixture, which is important to understand the mechanisms underlying improved P uptake in cereal/legume intercropping.