The role of cover crops in enhancing soil health and biodiversity in Mediterranean vineyards

Soil health is a priority in European policies, such as the EU Soil and Biodiversity Strategies for 2030, owing to land degradation and climate change, with Mediterranean vineyards being especially vulnerable because of their low soil organic matter content and risk of erosion. To improve sustainability, cover crops are increasingly used as alternatives to conventional tillage with bare soils. This study assessed the effects of different ground cover strategies on soil health, grape production, and biodiversity in Vitis vinifera cv. Tempranillo vineyard (D. O. Ribera del Duero, Spain). Four soil management systems were compared in 2021–2022: conventional tillage (CT), natural green cover (NGC), a sown grass–legume mixture (SGC), and a sown grass–flower mixture (FGC), in a randomized block design with four replicates. Surface soils (0 cm–20 cm) were sampled in spring 2022 and analyzed for pH, EC, organic matter, total nitrogen, soluble nutrients, microbial biomass, and enzymatic activity, as well as SPAD measurements to monitor plant development, yield, and grape quality. The yield decreased by 75% under FGC compared to that under CT. Soil Organic Carbon (SOC) increased by 57% in SGC compared to CT. Cover crops reduced grape yield but improved quality, notably by increasing anthocyanin content in the must. They also improved the biodiversity of the vineyards and increased the organic carbon content of the soil compared to CT. However, they depleted available nutrients, particularly nitrates, and showed only limited effects on soil biological properties, such as enzyme activities. Overall, cover crops promoted ecosystem services but required trade-offs with yield and soil nutrient availability.