Use of metagenomics and metabolomics to quantify changes in rhizosphere soil microbial function in response to mulching regimes

Abstract The effects of distinct mulching regimes on the microbial functional properties and metabolic profiles of rhizosphere soil remain largely unknown. Here, we conducted metagenomic and metabolomic analyses to explore the microbial functional specificity and metabolic pathways under three mulching regimes, namely, traditional flat planting with non‐mulch (TP), ridge‐furrow plastic film mulching (RF), and plastic film mulching (PFM). Compared to TP treatment, RF and PFM treatments significantly improved the soil temperature and moisture content, stimulated the increase of five extracellular enzyme activities, thereby reducing soil nutrient content (soil pH, total N, soil organic carbon, NH 4 + ‐N, and NO 3 − ‐N) to meet crop demand for nutrients. In addition, RF treatment significantly decreased the relative abundance of nxr A, while increasing the relative abundance of nas A, thereby further decreasing NO 3 − ‐N content. However, RF and PFM treatments had no significant effect on the relative abundance of nir B, nir D, nrf A, and nrf H. Meanwhile, PFM and RF treatment stimulated the increase of extracellular enzyme activities accelerated microbial metabolism, thereby promoting the synthesis of metabolites involved in carbohydrate metabolism, lipid metabolism, nucleotide metabolism, and amino acid metabolism. Metabolomics and network analyses revealed that RF and PFM treatments not only enriched organoheterocyclic compounds, organic acids and derivatives, lipids and lipid‐like molecules, and organic oxygen compounds but also increased their relative abundance in the major modules. Overall, this study provides deep insights into how mulching regimes alter soil microbial functional potential and metabolic profiles, which may have predictable impacts on the rhizosphere soil nutrient cycling of agroecosystems under mulching systems in semiarid regions.