Aerated drip irrigation changes soil microbial functional potential and enhances soil organic carbon content

Aerated drip irrigation (ADI) is an important practice for promoting soil fertility and crop productivity in greenhouse vegetable production, yet little research has comprehensively investigated its effects on the functional traits of carbon (C)-cycling microorganisms. In this study, we sought to assess the potential efficacy of ADI in increasing soil organic C (SOC) by changing soil microbial communities and the expressions of genes associated with C cycling. To this end, we adopted a metagenomic approach to compare the effects of ADI with three dissolved oxygen concentrations (10, 15, and 20 mg L⁻¹) during a three-season tomato cultivation experiment in northern China. The results revealed that the 10 mg L⁻¹ treatment led to a significant increase in the abundance of korA/B genes (associated with the reductive tricarboxylic acid cycle) in the C fixation pathway, whereas the 15 mg L⁻¹ treatment increased the abundances of cbbL/R and coxL/S genes associated with the Calvin cycle and carbon monoxide oxidation, respectively. In addition, based on a co-occurrence network analysis, we observed a positive correlation between cbbL and coxS. Interestingly, r-selected microorganisms, such as Proteobacteria and Actinobacteria, characterized by rapid cell multiplication and high biomass production, were identified as the primary contributors to C fixation and were the main predictors of SOC pools. In contrast, the 20 mg L⁻¹ treatment was found to adversely influence C fixation, although the enhanced C degradation could be attributed to the extracellular enzymes secreted by K-selected microorganisms. Collectively, our findings indicate that ADI with dissolved oxygen concentrations ⩽ 15 mg L⁻¹ can promote SOC content by altering the life history strategies of r-selected microorganisms and genes associated with C fixation. These findings will provide valuable references for agroecosystem irrigation management, help improve soil fertility, and promote sustainable production.