Vigour-yield-quality relationships in long-term deficit irrigated winegrapes grown under semiarid conditions

Abstract

Regulated deficit irrigation (RDI) and partial root-zone drying irrigation (PRD) are two of the most-promising agronomic practices designed to increase water use efficiency (WUE) and berry and wine quality in field-grown wine grapes in Mediterranean semiarid regions. However, many growers have not yet taken advantage of the new irrigation techniques now available, which would enable them to efficiently manage irrigation in wine grapes with the aims of improving quality and making this crop more competitive and profitable. This study focused on finding significant relationships between several WUE indicators (from the leaf to the plant level) and relevant vine vigour, yield and berry quality traits in order to improve deficit irrigation management in wine grapes under semiarid conditions. Sustained deficit irrigation (SDI), RDI and PRD techniques were compared for 7 years (2006–2012), in field-grown Monastrell grapevines grafted onto 1103P in 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 PRD (PRD-1); and a more-severe RDI strategy (90–144 mm year−1) under conventional drip irrigation (RDI-2) and under PRD (PRD-2). The SDI enhanced root system development and vine vigour, improved technological berry quality but lowered WUE and berry polyphenolic content, compared to deficit irrigation (DI). In contrast, PRD and RDI resulted in lower root growth, vine vigour and leaf-plant canopy water use, but improved cluster microclimate and increased WUE and berry polyphenolic content. Among the DI treatments, the PRD-1 strategy was the one which most improved the long-term vine performance. The most-restrictive DI strategies (PRD-2 and RDI-2) did not give a substantial improvement in WUEyield (kg m−3) or berry quality. Significant interactive effects of irrigation volume (high vs. low) and irrigation placement (PRD vs. RDI) indicate distinct PRD effects on long-term yield, WUE and berry quality, depending on the volume of water applied in the wet root zone and the soil total water availability. Significant vigour-quality relationships were established. We identified a range of optimum physiological and agronomical thresholds in order to develop long-term, efficient deficit irrigation strategies in Monastrell vineyards under semiarid conditions.