Improving berry and wine quality attributes and vineyard economic efficiency by long-term deficit irrigation practices under semiarid conditions

Sustained deficit irrigation (SDI), Regulated deficit irrigation (RDI) and partial root zone irrigation (PRI) were compared for seven years (2006–2012), in field-grown Monastrell grapevines grafted onto 1103P, in South Eastern Spain. The aim was to distinguish the effects of deficit irrigation per se (irrigation volume) from specific PRI effects (placement of water) on long-term yield-WUE response and berry and wine quality. In addition, we compare several financial indices using cost-benefit analysis to determine economic efficiency and the long-term profitability of producing Monastrell wine grapes under SDI, RDI and PRI in semiarid conditions of SE Spain. Five treatments were applied: SDI irrigated at 60–40% ETc (crop evapotranspiration) for the whole season (308-211 mm year −1 ); a moderate RDI strategy (110–191 mm year −1 ) under conventional drip irrigation (RDI-1) and under PRI (PRI-1); and a more-severe RDI strategy (90–144 mm year −1 ) under conventional drip irrigation (RDI-2) and under PRI (PRI-2). In general, the SDI strategy, involving more irrigation, improved technological berry quality a nd financial efficiency, to the detriment of WUE yield , berry and wine polyphenolic content. By contrast, long-term deficit irrigation strategies (PRI and RDI) increased WUE yield , berry polyphenolic content and wine quality, but at the expense of lower financial efficiency compared to SDI. PRI-2 and RDI-2 (the most-severely water-stressed vines) showed greater carryover effects of water stress, yield reduction and lower overall berry and wine quality (including technological and phenolic composition) than the moderately-water-stressed vines (RDI-1 and PRI-1). Among the DI treatments, the PRI-1 strategy was the one which most improved the long-term yield-quality-WUE response, water productivity and berry anthocyanin content and was also the most economically profitable. In contrast, long-term PRI-2, although it improved some technological quality attributes and phenolic characteristics and enhanced nutraceutical properties in Monastrell berries and wines (flavonols, malvidins, acylated anthocyanins and amino acids) compared to RDI-2, did not have a positive effect on WUE yield and yield (yield, cluster and berry weight decreased in some years) and its implementation in the current market conditions, was economically unviable. The significant interaction between irrigation volume (high vs. low) and irrigation system (PRI vs. RDI) indicate that the response to PRI also depended on the volume of water applied in the wet root zone and the soil total water availability. We identified an optimum irrigation water volume range (134–200 mm year −1 ) and an optimum range of yield (8000–12000 kg ha −1 ) in order to develop long-term, efficient and economically-profitable deficit irrigation strategies in Monastrell vineyards under semiarid conditions.