Drought modulates soil hydraulic, biological, and physicochemical responses to one-off tillage in a long-term cover-cropped Mediterranean vineyard

Sustainable soil management is a crucial factor to maintain soil health and long-term functionality in vineyards. In Mediterranean climates, cover crops have become a sustainable alternative to conventional tillage due to their positive effects on soil structure, water retention, and biological activity. Severe drought episodes are increasingly prompting growers to incorporate tillage to reduce water and nutrient competition between cover crops and grapevines. However, the immediate consequences of this practice on soil attributes remain poorly understood. To evaluate whether reintroducing tillage is a viable short-term strategy to relieve drought-induced water competition without compromising soil health, this study assessed the effects of a single tillage event on soil hydraulic properties (water retention curve, unsaturated hydraulic conductivity, Ku and field-saturated soil hydraulic conductivity, Kfs), physical and chemical properties (bulk density, total porosity, pore size distribution, total organic carbon, pH, CaCO 3 ) and biological properties (dehydrogenase and β-glucosidase activity) in a long-term cover-cropped organic vineyard of Vitis vinifera L. cv. Cabernet Sauvignon in Raïmat (Lleida, Spain), under commercial and survival water regimes. Soil water content dynamics were monitored, focusing on the April-June period when cover crop competition for water is greatest. Tillage reduced bulk density by 4.3% (1.35 ± 0.01 vs. 1.41 ± 0.02 g cm −3 , p = 0.020) and increased total porosity by 6.5% (0.49 ± 0.01 vs. 0.46 ± 0.01, p = 0.029) relative to cover crop, with no significant differences at field capacity (p = 0.352) or permanent wilting point (p = 0.264). Kfs was significantly higher under tillage regardless of water regime. Neither dehydrogenase nor β-glucosidase activity showed a significant reduction under tillage, suggesting that the measured biological indicators were not compromised by the one-off disturbance. However, β-glucosidase was significantly lower under survival, while dehydrogenase and total organic carbon showed no differences between managements. Organic matter content was significantly higher under commercial than survival irrigation, indicating that water regime was the main driver of this change. Overall, these results suggest that introducing tillage in a long-term cover-cropped vineyard primarily alters soil hydraulic properties, though these physical changes appear transient rather than a durable structural improvement.