Responses of diazotrophic network structure and community diversity to alfalfa-maize intercropping are soil property-dependent.

Introduction: Intercropping and soil properties both affect soil diazotrophic communities. However, the specific effects that alfalfa-maize intercropping has on diazotrophic networks and community diversity under different soil properties remain unclear.

Methods: In this study, we investigated the soil diazotrophic communities of two crop systems, alfalfa monoculture (AA) and alfalfa-maize intercropping (A/M), in two sites with similar climates but different soil properties (poor vs. average).

Results And Discussion: The diazotrophic network complexity and community diversity were higher at the site with poor soil than at the site with average soil ( < 0.05). Community structure also varied significantly between the sites with poor and average soil ( < 0.05). This divergence was mainly due to the differences in soil nitrogen, phosphorus, and organic carbon contents between the two sites. At the site with poor soil, the A/M system had lower diazotrophic diversity, lower network complexity and greater competition between diazotrophs than the AA system ( < 0.05) because intercropping intensified the soil phosphorus limitation under poor soil conditions. However, in the average soil, it was the A/M system that had an altered diazotrophic structure, with an increased abundance of 11 bacterial genera and a decreased abundance of three bacterial genera ( < 0.05).

Conclusion: Our results indicated that the effects of alfalfa-maize intercropping on diazotrophic communities were soil property-dependent.