Maize-potato residue mixing in agricultural soils enhances residue decomposition and stable carbon content by modifying the potential keystone microbial taxa

Microbe-regulated organic residue decomposition is a central hub of carbon (C) cycling in ecosystems. However, little is known about the changes in organic C composition and its microbial mechanisms during mixed crop residue decomposition in agroecosystems. We conducted a field litterbag experiment to explore the changes in organic C chemical structure and their associations with microbial communities during mixed (1:1 maize:potato residues based on dry matter mass) and single-species residue decomposition in agricultural soils. Compared with single-species residues, mixed residues exhibited a positive non-additive effect, specifically higher mass loss, and more recalcitrant organic C composition. Structural equation modelling combined with network analysis suggested that residues mixing modified bacterial keystone taxa, augmented the activity of C-degrading enzymes such as & beta;-glucosidase, and increased stable C content during mixed residues decomposition. Thus, this study highlights the potential advantages of applying residue mixtures to agri-cropping soils to increase the relative amount of persistent aromatic compounds derived from their decomposition and the importance of bacterial keystone taxa during residue decomposition.