Addressing Water Stress and Climate Variability in the Mediterranean: Study of Regulated Deficit Irrigation (RDI) and Non-Irrigation (NI) in Tempranillo and Cabernet Sauvignon ( Vitis vinifera L.)

Climate variability in Mediterranean viticultural areas, primarily attributed to climate change, will significantly impact water requirements, consequently leading to changes in irrigation management. The primary aim of this study was to assess the response of the Tempranillo and Cabernet Sauvignon grape varieties when subjected to deficit drip irrigation (RDI), in comparison to non-irrigation (NI), during various climatic years. The defined irrigation strategies involved water application equivalent to 35% and 80% of the (ET0 (reference crop evapotranspiration) × Kc (crop coefficient)). The ecophysiology of both grapevines was evaluated through the measurement of stomatal conductance (gs), sap flow, transpiration, leaf water potential (LWP), and CO 2 assimilation (A). Additionally, essential parameters including the crop coefficient (Kc), transpiration, and intrinsic water use efficiency were calculated. The information gathered from the pressure–volume curves of Cabernet Sauvignon and Tempranillo encompassed the osmotic potential at full turgor (γπ100), osmotic potential at turgor loss or 0 turgor (γπ0), water content at turgor loss (CHR0), modulus of elasticity (ε), and water potential at turgor loss 0 (γ H 0). The results enable a precise estimation of the water requirements for irrigation, contributing to a deeper understanding of the physiological responses of both varieties. This comprehension aids in assessing the sustainability of these vineyards amidst unexpected changes in the global mean surface temperature.