Effects of Three Irrigation Strategies on Gas Exchange Relationships, Plant Water Status, Yield Components and Water Productivity on Grafted Carménère Grapevines

In the Chilean viticultural industry, Carménère is considered an emblematic cultivar that is cultivated mainly in arid and semi-arid zones. For this reason, it is necessary to use precise irrigation scheduling for improving water use efficiency (WUE), water productivity (WP), yield and wine quality. This study evaluated the effects of three deficit irrigation strategies on gas exchange variables, WUE, WP and yield components in a drip-irrigated Carménère vineyard growing under semi-arid climatic conditions during two consecutive seasons (2011/12 and 2012/13). The irrigation strategies were applied in completely randomized design from fruit set (S) to harvest (H). The first irrigation strategy (T1) involved continuous irrigation at 100% of actual evapotranspiration (ET(a)) from S to the veraison (V) period and at 80% of ET(a) from V to H. The second irrigation strategy (T2) involved irrigation at 50% of ET(a) from S to H and the third one (T3) involved no-irrigation from S to V and at 30% of ET(a) from V to H. The results indicated that there was a significant non-linear correlation between net CO(2) assimilation (A(N)) and stomatal conductance (g(s)), which resulted in three zones of water stress (zone I = g(s) > 0.30 mol H(2)O m(-2)s(-1); zone II = between 0.06 and 0.30 mol H(2)O m(-2)s(-1); and zone III = g(s) < 0.06 mol H(2)O m(-2)s(-1)). The use of less water by T2 and T3 had a significant effect on yield components, with a reduction in the weight and diameter of grapes. A significant increase in WP (7.3 kg m(-3)) occurred in T3, which resulted in values of WUE that were significantly higher than those from T1 and T2. Also, a significant non-linear relationship between the integral water stress (SI(Ψ)) and WP (R(2) = 0.74) was established. The results show that grafted Carménère vines were tolerant to water stress although differences between cultivars/genotypes still need to be evaluated.