Objective   Effect of arbuscular mycorrhizal fungi (AMF) and organic fertilizer applied in sweet corn field on the microbial genes relating to the carbon (C) cycling in the rhizosphere was studied to decipher the biological mechanism and the soil C-transformation.

  Method   Seven treatments with triplicates each were applied on the sweet corn fields including (1) no N fertilizer (CK), (2) optimized fertilization (OF), (3) organic N fertilizer to replace 10% of chemical N fertilizer (ORF10), (4) organic N fertilizer to replace 20% of chemical N fertilizer (ORF20), (5) ORF10 with added Glomus versiforme (ORF10+AMF), (6) ORF20 with added G. versiforme (ORF20+AMF), and (7) CK with added G. versiforme (CK+AMF). Genes related to C-cycling in the treated rhizosphere soils were analyzed using GeoChip 5.0 technology.

  Result  Addition of AMF in fertilizing the sweet corn plants significantly increased the yield. By adding AMF to CK, ORF10, and ORF20, the treatments increased the number of fresh buds on the plants by 32.6%, 8.6%, and 8.9%, respectively. The results of gene sequencing on the soil samples showed that the AMF/organic fertilizer combinations significantly altered the structure of the microbial C-cycle genes. The signal strength of key functional genes associated with C-cycling, such as C-decomposition, C-fixation, and methane metabolism, were generally stronger under CK+AMF and ORF20+AMF than the other treatments. According to the redundancy analysis, the respiration, total nitrogen, pH, total potassium, organic matter, available phosphorus, and total phosphorus in rhizosphere soil were the major environmental factors affecting the functions of the C-cycle-related genes.

  Conclusion  The application of organic fertilizer and G. versiforme in sweet corn field significantly increased the fresh bud count on the plants. It changed the structure of the microbial C-cycle genes in rhizosphere soil positively affecting the decomposition and fixation of C as well as the methane metabolism of the ecosystem.