Objective To investigate the effects of inoculation with synthetic microbial communities on growth, nitrogen (N) and phosphorus (P) uptake of monocultured or intercropped maize and soybean, and provide a theoretical basis for utilizing efficiently microbial inoculants to enhance crop yield.

Method Using unsterilized soil in monoculture and intercropping systems of maize and soybean, a pot experiment, including eight treatments of non-inoculated control (CK), single inoculation with arbuscular mycorrhizal fungi (AM fungi, A), rhizobia (R) or Bacillus (B), dual inoculation with AM fungi and rhizobia (A+R), AM fungi and Bacillus (A+B), or rhizobia and Bacillus (R+B), and triple inoculation with AM fungi, rhizobia and Bacillus (A+R+B), was conducted to determine plant dry weight, N and P contents, root traits, mycorrhizal colonization rate, nodule traits, pH and acid phosphatase activity in the rhizosphere.

Result The different combinations of dual inoculation exhibited better inoculation effects. Compared with CK, dual inoculations of A+B and R+B increased plant dry weight by 14.11% and 13.31%, N content by 30.02% and 20.56%, and P content by 17.77% and 16.84% in the monocultured maize, respectively. Dual inoculation of R+B increased plant dry weight, N and P contents by 28.53%, 33.55% and 17.29% in the monocultured soybean, respectively. Compared with dual inoculation of A+B, plant dry weight of the monocultured or intercropped maize with triple inoculation of A+R+B significantly reduced. Compared with dual inoculation of R+B, plant dry weight and N and P contents of the monocultured soybean with triple inoculation of A+R+B also significantly reduced. Intercropping significantly increased plant dry weight and N and P contents of maize (except for the A+R+B treatment). Dual inoculation of R+B promoted N and P uptake and plant growth of the intercropped soybean, and partially alleviated the inhibitory effect of intercropping on soybean growth. Compared with CK, Dual inoculation of R+B promoted mycorrhizal colonization rate of the intercropped maize and nodulation of monocultured or intercropped soybean plant. Additionally, dual inoculation of A+B and R+B, as well as intercropping promoted maize root growth, and altered rhizosphere processes of both maize and soybean, thereby enhanced crop acquisition of N and P.

Conclusion In the complex environment of soil, single inoculation has limited effectiveness, while dual inoculations with complex microbial communities and intercropping play a significant role in improving N and P acquisition and promoting maize growth.