Partner quality matters—overyielding in a maize/soybean mixture depends on the initiator of common mycorrhizal networks

Aims: Cereal/legume intercropping has advantages in yield and nutrient uptake. However, how common mycorrhizal networks (CMNs), formed by arbuscular mycorrhizal fungi (AMF) play a role in those benefits has not been fully clarified. This study aimed to explore how CMNs initiated by different host plants affected plant performance and nutrient acquisition in a maize/soybean mixture. Methods: Microcosms with three compartments were used; these were separated by 30-µm nylon mesh. Two compartments were root compartments (RCs), and the third compartment was a hyphal compartment (HC). One RC was inoculated with the AMF Rhizophagus irregularis and the plant in this compartment was referred to as CMNs donor, and the plant in the other RC compartment as CMNs receiver. Results: Maize biomass was twice that of soybean. Nitrogen (N) and phosphorus (P) content of both maize and soybean were higher in the presence of CMNs compared with the treatment without AMF. When maize was the CMNs donor, shoot biomass, N and P content of the maize/soybean mixture were higher than the expected biomass, N and P content based on monocultures, suggesting overyielding. However, the overyielding was not observed when soybean was the CMNs donor. Conclusion: Overyielding in a maize/soybean mixture depends on the initiator of CMNs. With maize as CMNs donor, both species in the mixture benefited from CMNs compared with monocultures.