Water Versus Source–Sink Relationships in a Semiarid Tempranillo Vineyard: Vine Performance and Fruit Composition

Abstract

Grapevine yield and fruit composition largely depend on vine water status, which can be manipulated, especially in semiarid climates, by irrigation strategies and training systems. The objective of this research was to examine the influence of canopy height on vine growth, yield, and berry traits of Tempranillo vines under different degrees of water stress. Two canopy heights and three irrigation strategies, similarly applied in the two training systems, were tested in combination. Over two years (2010 and 2011), elevating the canopy resulted in a 26% increase in leaf area per vine but also in greater water stress. As a consequence, yield was reduced by an average of 12% in the elevated canopy for the three irrigation levels, due to lower cluster and berry weight; berries from the elevated canopy had greater total soluble solids and anthocyanin concentrations, lower total acidity, and lower malic and tartaric acid concentrations. There were only slight differences in yield under the different irrigation regimes. However, berry anthocyanin concentrations were higher when an early deficit irrigation strategy was applied. Midday stem water potential, rather than the leaf-area-to-yield ratio, better explained differences in vine performance and fruit composition between the treatments. This suggests that vine performance in the study area is more influenced by water availability than by the amount of sunlight intercepted.