Distinct roles for soil bacterial and fungal communities associated with the availability of carbon and phosphorus under aerated drip irrigation

Soil bacteria and fungi play key roles in organic matter decomposition and nutrient turnover. Aerated drip irrigation (ADI) is beneficial for improving soil nutrients but its effects on bacterial and fungal communities are less known. In this study, a two-season ADI field experiment comprising three dissolved oxygen concentrations (10, 15, and 20 mg·L–1, referred to as A1, A2, and A3) and a control treatment (groundwater without aerated, CK) was conducted in a tomato plantation in Shandong, China. Soil bacterial and fungal communities were examined using high-throughput sequencing targeting 16 S rRNA and ITS genes, respectively. The ADI treatments increased fungal community diversity but did not significantly affect bacterial community diversity. However, bacterial communities were more connected within the module, with more stable network structures in the ADI treatments. In contrast, fungal networks had lower modularity values and a significant negative correlation with soil available phosphorus (AP). The ADI treatments increased the bacterial phylum Gemmatimonadetes and Firmicutes and a few aerobic taxa and strongly enriched the fungal phylum Mortierellomycota and phosphorus-dissolving taxa (Humicola, Mycothermus, and Myceliophthora). In addition, the A2 treatment enhanced functional groups related to carbon and phosphorus cycling while decreasing Plant Pathogen functional groups. The most important environmental factors affecting bacterial and fungal communities were soil organic carbon (SOC) and AP, respectively. Structural equation modeling (SEM) demonstrated that ADI directly affected soil bacterial and fungal communities and indirectly promoted SOC, AP content, and tomato yield. Overall, our findings highlight the importance of bacterial and fungal taxonomic communities, co-occurrence networks, and functions related to regulating soil carbon and phosphorus availability, providing novel evidence for the application of ADI to improve soil fertility and crop productivity.