Response of grapevine cv. ‘Brancellao’ and ‘Sousón’ to supplementary irrigation: Water relations, vine growth, yield and berry and wine composition

Growers are concerned about the negative impacts on vine yield and berry quality caused by global warming. Irrigation systems are increasingly being installed in vineyards in order to counteract those problems. Therefore, an efficient irrigation management is required. In this context, a field experiment was carried out over three years (2012-2014) on red Vitis vinifera (L.) cv. ‘Brancellao’ and ‘Souson’ in order to assess the effects of supplementary irrigation on vine performance and must and wine composition. Rain-fed vines were compared with a treatment irrigated to 40% of potential evapotranspiration (ET0) from bloom to two/three weeks before harvest. Both cultivars showed less negative stem water potentials under irrigation than under rain-fed conditions; however, stomatal conductance was similar between treatments. Yield was unaffected by irrigation, whereas pruning weight tended to increase in both cultivars. Must and wine composition, including amino acids and volatile compound concentrations, were mostly unaffected by irrigation. Water productivity was higher under rain-fed conditions and, as a consequence, gross incomes were not increased by irrigation. Therefore, irrigation does not seem an economically viable agricultural practice under the conditions of this trial.