Effects of deficit irrigation on the performance of grapevine (Vitis vinifera L.) cv. ‘Godello’ and ‘Treixadura’ in Ribeiro, NW Spain

•Leaf and stem water potential were lower under rain-fed conditions.•Stomatal conductance and chlorophyll fluorescence were unaffected by deficit irrigation.•Yield components showed opposite trends in cv. Godello and Treixadura.•No significant differences between treatments in berry and wine attributes.•Results indicated that irrigation might not be economically viable under the conditions of this trial. Galicia is a region located in NW Spain characterized by high rainfall amounts; however, climate change is altering the temporal and spatial distribution of rainfall. Thus, vinegrowers are concerned about this climate variability that may affect grape production and quality and, therefore, drip irrigation systems are increasingly being installed in Galician vineyards. Hence, the development of efficient irrigation management practices is required. In this regard, a field experiment was carried out over three seasons (2012–2014) on white Vitis vinifera L. cv. ‘Godello’ and ‘Treixadura’ in order to assess the effects of deficit irrigation on vine performance and must and wine composition. Rain-fed vines were compared with a treatment irrigated to 50% of the estimated crop evapotranspiration (ETc) from bloom to two weeks before harvest. Both cultivars showed more positive plant water status under irrigation than under rain-fed conditions; however, stomatal conductance and chlorophyll fluorescence attributes were similar between treatments. Yield was unaffected by irrigation except for Treixadura cultivar in 2014 (25% increase). On the contrary, irrigation increased pruning weight, around 15%, for both cultivars. Total soluble solids of the must decreased and total acidity increased with irrigation; however, the wines were very similar between treatments. Water productivity was higher under rain-fed conditions for Godello, which led to similar gross incomes between treatments but with a lower production cost for rain-fed. In the case of Treixadura, significantly higher gross incomes were estimated for irrigation only in the last year of studies, which may not justify the use of irrigation. Therefore, irrigation does not seem an economically viable agricultural practice under the conditions of this trial.