Influence of rootstock and vine spacing on root distribution, vine growth, crop yield, fruit and wine composition, canopy microclimate and wine quality of Cabernet Sauvignon
In 1991 and 1992, the effect of seven rootstocks (AxR#l, 110R, 5C, 3309, 420A, 1616, and 039-16) grafted to Cabernet Sauvignon in combination with three between row spacings (2, 3, and 4 m) and two in-row spacings (1 and 2 m) on root and shoot growth, water utilization, leaf, fruit and wine composition, crop yield and wine quality were evaluated in a field plot trial established at the Oakville Experimental Vineyard in 1987. The data revealed that the above seven rootstocks can be divided into three groups based on rooting depth, pruning weights and crop yield. 110R, AxR, and 039-16 rootstocks had the deepest roots, made the most vegetative growth and had the highest crop yield; 5C, 3309, and 1616 were intermediate in growth and yield, and 420A had the least amount of shoot growth and lowest yield. Neutron probe measurements also showed that AxR, 039-16, and 110R were able to utilize water down to depths of 210 cm (-7 ft); 3309, 5C, and 1616 mainly used water at depths between 30 and 150 cm and 420A mostly used water at depths less than 120 cm. In another field trial comparing St. George, AxR, and 110R it was shown that St. George had greater root density and deeper roots than 110R and AxR#l. There were relatively little differences in fruit composition at harvest between the seven rootstocks. 039-16 consistently had the highest pH, K+, and malic acid of the seven rootstocks. 110R fruit was the first to ripen and had the highest titratable acidity and anthocyanin pigment per berry, however, on a per gram basis, the level of anthocyanin did not differ significantly between rootstocks. In leaf petiole analyses, 039-16 had the highest level of K\ Ca*+, NO;, and Ca/mg ratio, and 420A was consistently the lowest in K at both bloom and veraison. The average crop yield of vines from rows spaced 2, 3, and 4 m apart was 7.7, 5.9, and 5.1 tons/ac, respectively, and for in-row spacings of 1 and 2 m, 7.0 and 5.5 tons/ac, respectively. Fruits from vines spaced 3 and 4 m apart between rows were significantly higher in sugar and pH than 2 m row spacing, however, TA, malic acid, K, and anthocyanin in fruits did not differ between row spacing treatments. Fruits from vines spaced 1 m apart within rows were significantly higher in pH, K, malic acid, and anthocyanin/berry than fruits from vines spaced 2 m apart. Wines made from Cabernet Sauvignon grafted onto different rootstocks differed in composition. 039-16 wines had the highest pH and hue and less red and total coloration than 5C, 3309 and 110R. 5C wine had the lowest pH and hue and the highest level of anthocyanin and total coloration of the above four stocks. Wines made from vines at two meter spacing generally had higher titratable acidity and level of anthocyanin than four meter row spacing wines. Within row vine spacing had little effect on wine composition. Duo-trio tasting of wines made from the 1992 vintage showed that 5C and 3309 wines could generally be distinguished from 110R and 039-16 wines. 5C wine had the most fruity character, whereas 110R and 039-16 wines were more vegetative and astringent in character. 3309 wine had the most herbal/spicy character of the four rootstocks. For 5C rootstock, closer vine spacing (2 x 1 and 2 x 2 m) wines could be distinguished from wider vine spacing (4 x 1 and 4 x 2 m) with a preference for the closer vine spacing wines. However, for 110R rootstock, wines did not differ between row and vine spacing in duo-trio taste comparisons.