In semi-arid areas, irrigation is usually mildly supplemented to wine grapes by drip systems, in order to confer moderate drought stress. This practice ensures the development of high-quality grapes- otherwise hampered by overly abundant water conditions, without damaging the vegetative and productive perennial development. This work deals with the question of the proper irrigation initiation time, and its effect on wine quality- should irrigation initiate with bud break or rather once stress conditions appear?
Our results show that initiating irrigation late in the growing season causes the development of lower midday stem water potential (SWP) in these vines after irrigation initiation, as compared to vines irrigated earlier in the season. Consequentially, these vines tend to produce a lower number of bunches per vine and smaller berry size, leading to lower yields. Nevertheless, the wines produced from the late-irrigated treatments had higher phenolic content, primarily due to higher levels of catechin and epicatechin. The late irrigation treatments also led to wines with higher color intensities compared to those irrigated at earlier stages, due to higher levels of most anthocyanins. Finally, we show that the wine sensory score given by professional winemakers for wines made from delayed irrigation treatments was approximately five points higher compared to wines made from the early season irrigation treatment.