Long-term effects of different irrigation strategies on yield components, vine vigour, and grape composition in cv. Cabernet-Sauvignon (Vitis vinifera L.)

There are still some traditional vine-growing areas in Spain in which water-stressed vines are considered to produce berries with the highest quality must. To assess vine response to water availability, measured in terms of crop yield, vegetative development, and grape composition, five different irrigation treatments were evaluated over a five-year period in a Cabernet-Sauvignon vineyard in the Madrid region (Spain): no-irrigation (T0), water provided at 20?% of the reference evapotranspiration (ETo) (T20), water provided at 45?% of the ETo (T45), water provided at 20?% of the ETo until veraison and at 45?% thereafter (T20-45), and water provided at 45?% until veraison and 20?% thereafter (T45-20). A yield increment was observed with increasing water volumes. The T45 vines returned a consistent yield of around 8 t/ha, and a mean shoot weight of 30–50?g. The T0 and T20 plants showed reduced yields and vegetative growth in most years (yields being the most acutely affected). Berry weight was the yield component most influenced by water availability. In years of low rainfall, fertility was markedly reduced in the T0 vines. Providing a smaller irrigation volume before or after veraison (the T20-45 and T45-20 treatments) led to reductions in berry weight, cluster weight, and shoot weight over the last 3?years of the trial. Berry composition was almost unaffected by irrigation strategy. Taking into account yield, water use efficiency, and berry composition, the T45-20 treatment was the most efficient irrigation strategy.