Effect of irrigation on water status, growth and yield of white winegrapes in the Douro demarcated region

Abstract

The hot and dry climate of the Douro Demarcated Region (DDR), Portugal, particularly during the summer, induces soil water deficits that influence the growth and development of grapevines. Therefore, controlling the soil water supply, by means of irrigation, can regulate the water status of winegrapes, which can bring changes in physiological processes within the plant and thus in vegetative growth, yield and quality. As a result the present study was carried out in a commercial vineyard (Moscatel-Galego-Branco, syn. Muscat à Petits Grains) during two growing seasons (2009 and 2010) in the DDR (41° 15’ N, 7° 28’ W, 600 m). The experimental design includes rainfed plots (traditional farming in the region) and two drip irrigated regimes using predawn leaf water potential (Y_pd) as reference: weak or no water stress (Y_pd > -0.3 MPa) and moderate water stress (-0.3 MPa ≥ Y_pd ≥ -0.5 MPa). The main objective is to evaluate the responses of crop growth, yield and quality to different water regimes. Additionally, the performance of midday leaf water potential is evaluated. The water treatments resulted in significant differences in water status and vegetative and reproductive growth. Non-irrigated vines showed significantly lower leaf area, pruning weight, yield and alcohol content of the wine. However, no differences between irrigated treatments are generally found. The study confirms the usefulness of Y_pd as a crop stress indicator and suggests that a mild water deficit should be a functional strategy (deficit irrigation) to obtain an increased balance between vegetative growth and yield/quality in the region.