Effect of different irrigation strategies on vine physiology, yield, grape composition and sensory profiles of Vitis vinifera L. Cabernet-Sauvignon in a cool climate area

摘要

Aim: The efficacy of partial root zone drying (PRD) and regulated deficit irrigation (RDI) on vine physiology, yield components, fruit composition and wine sensory profiles of ‘Cabernet-Sauvignon’ was investigated in a cool climate region in Ontario, Canada.Methods and results: Field experiments were conducted in a Cabernet-Sauvignon block in Niagara-on-the-Lake, ON Canada between 2006 and 2008. There were five treatments : non-irrigated control, PRD, full irrigation [100 % of crop evapotranspiration (ETc)] and two levels of RDI (50 and 25 % ETc). Treatments started immediately after fruit set and continued until post-veraison. Soil and vine water status were apparently controlled not only by the amount of water but also by the irrigation strategy used. In the PRD treatments, soil moisture, leaf water potential, and transpiration rate were generally lower than in 100 % ETc but higher than non-irrigated and RDI treatments. Almost all treatments were different than in non-irrigated vines in fruit composition and wine sensory attributes. Wine sensory attributes differed considerably due to the amount of irrigation water applied in 2007. RDI strategies were more consistent than the PRD treatments in their effect on vine water status, grape composition and wine sensory profiles. Inconsistent patterns across seasons for some variables indicated that besides soil and vine water status, there were other factors that impacted vine physiology, yield components and berry composition.Conclusions: RDI treatments improved wine quality when compared with full or either non-irrigated treatments. Overall, use of RDI irrigation or PRD during dry and warm years can improve grape composition in cool climates.Significance and impact of the study: To the best of our knowledge, this is the first evaluation of PRD and RDI on Cabernet-Sauvignon in a cool humid climate. It suggests that although RDI strategies are more effective, PRD also has value, particularly in dry seasons. IntroductionIrrigated vineyards are located mostly in “The New World”, in areas where there is low rainfall during the growing season, and moisture in the soil profile is insufficient for healthy vine growth (McCarthy et al., 2002). Despite using irrigation, “The New World” consistently produces very high quality wine, which would not be possible under natural conditions. Drought is not normally an issue in north-eastern North America. However, in the last decade, frequency of water shortages during active vegetative growth has increased. Exposure of vines to some degree of water stress during vegetative growth has been reported in cool wine regions (Van Leeuwen and Seguin 2006, Zsófi et al. 2009). In winegrape production, both drought and excess water should be avoided due to their negative effect on wine quality (Van Leeuwen and Seguin 2006).Vitis vinifera L. is considered a species adapted to drought stress. However, when water deficit is combined with other climatic factors such as high light intensity, temperature and vapour pressure deficit, it could become a major constraint for leaf photosynthesis (Flexas et al. 1998). Water stress can determine changes in leaf physiology, including a reduction in stomatal conductance, photosynthesis and transpiration (Matthews and Anderson 1989). Grapevine vegetative growth is the first process affected by water restriction. Water deficits reduce shoot growth, yield, fruit size, and as a consequence, physiological changes, fruit composition and wine sensory attributes are likewise altered (Roby and Matthews 2004). Studies in California revealed that different levels of water deficits generated significant differences in appearance, flavour, taste, and aroma among Cabernet-Sauvignon wines (Chapman et al. 2004). Water restriction could favour polymerization of tannins, and subsequently decrease astringency and bitter flavours related to tannin monomers (Ojeda et al. 2002).Drought stress could be an issue in the vineyard that leads to economic losses if it is extended to a prolonged period of time. Severe water stress applied to container-grown Cabernet Franc vines decreased yield by 94% due to reducing number of berries per cluster and berry weight (Hardie and Considine, 1976). Matthews and Anderson (1989) found yield reductions in Cabernet-Sauvignon under water deficits, and suggested that the large differences in yield occurred due to alterations in berry growth pattern. However, yield reductions resulting from prolonged water deficits depended on the stage of berry development when drought occurred (Hardie and Considine 1976). For red winegrapes, some degree of water deficit during the growing season is beneficial for quality (Williams and Matthews 1990). However, there are contradictory studies suggesting that fruit composition and wine quality of Cabernet-Sauvignon could be more related to variations in yield (Keller and Hrazdina 1998), and this response could depend on how and when the yield variation is establi