Yield and berry composition of 'Tempranillo' grapevines exposed to deficit irrigation applied at different phenological stages

The correct use of deficit irrigation (DI) in viticulture for wine production represent an effective tool to improve berry composition at harvest. However, these effects are strongly dependent on the phenological stage when DI is applied and on the level of water stress induced. If water stress is too severe, berry composition is negatively affected. Severe water stress conditions can easily occur in vineyards located in dry areas when irrigation is withhold. Hence, the aim of this experiment was to study how withdrawing irrigation at two different phenological stages affects fruit yield and berry composition in a dry region. The experiment was carried out in Raimat (Lleida, Catalonia, Spain) on 'Tempranillo' grapevines. The experimental design was a complete randomized block design with three treatments and four blocks. Treatments were the following: a DI treatment in which vines received 0% of calculated evapotranspiration (ETc) between fruit set and veraison, whereas 100% of ETc was replaced with irrigation during the other phenological stages (hereafter PRE-DI treatment); a DI treatment in which vines received 0% of ETc between veraison and harvest, whereas 100% of ETc was replaced with irrigation during the other phenological stages (hereafter POST-DI treatment); a control treatment in which vines received 100% of ETc throughout the growing season (hereafter C treatment). Between fruit set and harvest, PRE-DI and POST-DI treatments allowed to save 41 and 45% of water applied with irrigation. Both DI treatments induced moderate water stress conditions (midday stem water potential decreased down to values between -1.5 and -1.3 MPa) in the phenological stages when irrigation was withhold. Harvest date was anticipated by PRE-DI treatment compared to POST-DI and C vines. PRE-DI induced a decrease in berry growth and fruit yield at harvest. POST-DI did not affect berry anthocyanin concentration at harvest.