Effects of Inter-row Grass on Soil Nutrient, Enzyme Activity and Microbial Community in Vineyard

This study investigated the effects of inter-row grass cropping on soil nutrients and microbial community structure in wine grape vineyards in the eastern foothills of the Helan Mountains, aiming to identify suitable cover crop species for the region. Using Vitis vinifera L. cv. "Chardonnay" as the test material, four cover crop species-Vicia sativa, Onobrychis viciifolia, Echinochloa frumentacea, and Lolium perenne -were planted between vine rows, with traditional clean tillage as the control. The surface soil properties, enzyme activities, and microbial community structure were analyzed. The results showed that compared with clean tillage, the inter-row grass cropping reduced the soil pH value of the vineyard, and the reduction range of Vicia sativa and Echinochloa frumentacea was the largest, with 12.83% and 13.40%, respectively. The contents of soil organic matter, total nitrogen, total phosphorus and available phosphorus were significantly increased in the inter-row grass cropping, and the best effects of Vicia sativa treatment were 9.15 g·kg^-1, 1.64 g·kg^-1, 19.30 g·kg^-1 and 72.61 mg·kg^-1, respectively. The soil alkali hydrolyzable nitrogen (AN) content of Onobrychis viciifolia treatment was the highest, which was 35.53 mg·kg^-1. Additionally, cover cropping enhanced the activities of soil enzymes, including catalase, urease, alkaline phosphatase, cellulase, sucrase, and amylase. Compared with clean tillage, the inter-row grass cropping increased the number of fungal and bacterial operational taxonomic units (OTUs). The Shannon, Simpson, and Chao1 indices of bacterial communities were elevated, while fungal community diversity showed no significant differences. The results of bacterial community composition showed that Proteobacteria (26.22%-32.98%), Bacteroidota (11.78%-16.83%) and Actinobacteriota (9.97%-17.29%) were the dominant phyla at the phylum level. Ascomycota (57.18%-85.11%) was the dominant phyla among fungi. Redundancy analysis indicated that amylase activity significantly influenced bacterial community structure, while AN content was the key factor affecting fungal communities. Principal component analysis (PCA) showed that the comprehensive scores of clean tillage, Vicia sativa, Onobrychis viciifolia, Echinochloa frumentacea and Lolium perenne were -2.268, 1.954, 1.455, -0.207 and -0.934, respectively, indicating that the best treatment effect is Vicia sativa. In conclusion, in the vineyards at the eastern foot of the Helan Mountains, inter-row grass cropping has certain improvement effects on soil physicochemical properties and enzyme activities, increased the number of microorganisms in the soil, and changed the community structure and diversity of bacteria and fungi to varying degrees, among which the planting of Vicia sativa and Onobrychis viciifolia have a better effects on soil.