Deciphering the microbial functional potential of aeration drip irrigation to enhance soil organic carbon content

Abstract

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 the effects on functional traits of carbon (C) cycling microorganisms. In this study, we sought to assess the potential efficacy of the ADI in enhancing soil organic carbon (SOC) content mediated via changes in microbial communities and the expression of genes associated with the carbon cycle. To this end, we adopted a metagenomics approach to compare the effects of ADI treatments 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 rTCA 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 Actinomycetes, 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 enhanced C degradation could be attributed to the breakdown of organic matter by 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 insights into agroecosystem irrigation management, specifically in improving soil fertility and promoting sustainable production.