Differential Effects of Cover Crops on Soil Nutrients and Microbial Communities in Marselan Vineyards

ABSTRACT Cover crops are increasingly adopted in vineyards to enhance soil health, yet their short‐term effects on soil nutrient cycling and microbial communities remain poorly understood, especially in specific cultivars such as Marselan. Here, we evaluated the impacts of five cover crop treatments—natural grass, Centaurea cyanus , Poa pratensis , Lolium perenne , and Medicago sativa —on soil physicochemical properties, enzyme activities, and microbial diversity compared to clean tillage in a vineyard in Ningxia, China. After one growing season, cover crops reduced the topsoil pH by 1.03%–3.67% compared to clean tillage and decreased available phosphorus content by 43.34%–56.14%. Changes in soil organic matter and alkali‐hydrolyzable nitrogen varied among treatments. The Lolium perenne treatment showed a significantly higher organic matter content of 15.10 g/kg compared to clean tillage, while all other treatments significantly reduced organic matter content, with natural grass treatment having the lowest value of 11.74 g/kg. In the Medicago sativa treatment, alkali‐hydrolyzable nitrogen content (0–20 cm: 75.83 mg/kg; 20–40 cm: 46.33 mg/kg) was significantly higher than that in clean tillage, whereas all other treatments significantly reduced alkali‐hydrolyzable nitrogen content. Although cover crops reduced the availability of some nutrients, they enhanced the soil's nutrient transformation capacity. Enzyme activities responded differentially: urease, alkaline phosphatase, and cellulase were stimulated, whereas catalase and sucrase were suppressed. Cover crops also increased the alpha diversity of both bacterial and fungal communities, with the Lolium perenne treatment showing the highest values. In the 0–20 cm and 20–40 cm soil layers, the alpha diversity under Lolium perenne was 10.16% and 3.96% higher for bacteria, and 17.75% and 13.86% higher for fungi, respectively, compared to clean tillage. Additionally, cover crops altered the composition of microbial communities, with functional predictions indicating a promotion of heterotrophic metabolism and a reduction in plant‐pathogenic fungal guilds. Mantel tests and partial least squares path modeling revealed that cover crops influenced microbial communities indirectly through changes in soil properties and enzyme activities rather than via direct effects. The results indicate that even short‐term cover crop cultivation can reshape the soil microbiome and its functions. Lolium perenne demonstrated the best overall performance in enhancing soil organic matter and promoting microbial diversity, while Medicago sativa showed a significant advantage in rapidly improving nitrogen availability. These findings provide mechanistic insights into soil–microbe interactions and offer practical strategies for sustainable vineyard management in semi‐arid regions.