Influence of Grass Mulching and Organic Fertilizer Addition on Soil Microbial Community Composition and Function in a 'Dongzao' Jujube (Ziziphus jujuba Mill. 'Dongzao') Orchard

Microorganisms play an important role in soil ecosystems; therefore, it is essential to explore the effects of grass mulching (GM, and the mulching plants all belong to Poaceae family) and organic fertilizer addition (OFA) on the structure and function of orchard soil microbial communities. In this study, we analyzed the effects of GM and OFA on soil's physical and chemical properties, bacterial community structure, and enzyme activity in a winter jujube orchard. GM markedly increased the soil water content and activities of beta-1,4-glucosidase (BG), fibrinose hydrolase, and beta-1,4-xylosidase. OFA promoted BG activity and decreased the pH of slightly alkaline soils more effectively than GM. GM and OFA substantially increased the relative abundances of Bacteroidota, Chloroflexota, and Bacillota while decreasing those of Acidobacteriota, Actinomycetota, and Nitrospirota. GM also significantly increased the relative abundance of Proteobacteria and decreased that of Verrucomicrobiota. The relative abundance of Bacillota, involved in cellulose decomposition, significantly increased after GM, whereas that of Bacteroidota, involved in animal faeces decomposition, significantly increased after OFA. We showed that GM and OFA improved microbial diversity and the number of operational taxonomic units (OTUs), energy metabolism, and cell membrane transport capacity and demonstrated the linkage between microbial community structure and function. GM can overcome challenges related to the lack of precipitation and improve soil fertility.