Municipal Solid Waste (MSW)-Compost Amendment Increases Diversity, Functional Activities, and Network Connectivity of a Vineyard Soil Microbiota

Sustainable agriculture increasingly relies on organic amendments that integrate circular economy principles. Municipal Solid Waste (MSW)-derived compost (MSW-compost) represents a promising candidate as soil amendment in viticulture, yet its impact on soil microbiota remains poorly investigated. This study assessed the effects of MSW-compost application on the bacterial microbiota of a Mediterranean vineyard soil over a twelve-month period, comparing two application methods (surface mulching and tillage incorporation). Soil DNA was analyzed by 16S rRNA gene metabarcoding, complemented by functional prediction (Picrust2) and the Tea Bag Index to assess soil decomposition activity. MSW-compost significantly increased alpha-diversity and affected beta-diversity (p = 0.001) of the microbiota, regardless of the application method, with significant effects persisting throughout the entire observation period despite a clearly diminishing trend. Devosia emerged as the hub taxon of the co-occurrence network and was increased by compost addition. MSW-compost application mode remarkably affected the microbial network, with mulched treatment leading to a more complex, denser, and more interconnected network. While a similar number of taxa were increased or decreased, functional prediction revealed a notable enrichment of metabolic pathways, both synthetic and degradative, in the MSW-compost amended samples; this finding was supported by the enhanced red tea decomposition data (p = 0.007). Our results indicate that MSW-compost acts as a beneficial soil amendment, simultaneously enhancing microbial diversity and soil decomposition activity. This study provides novel evidence supporting the use of MSW-compost as a sustainable tool for improving soil microbiological quality in productive vineyards.