Abstract
Manipulation of vine balance is widely practised to enhance grape and wine quality. Reported benefits from crop thinning are ambiguous. Studies were undertaken over two growing seasons (2006–2008) in Hawke’s Bay, a cool climate region of New Zealand, to investigate the influence of basal leaf and crop removal on fruit composition and wine quality and also the indices of vine balance associated with optimum quality. Three levels of basal leaf removal (LR) in the fruiting zone were used. Crop removal (CR) achieved average reductions of 15 % for moderate and 35 % for the severe level below the average non thinned yield of 17.5 t/ha. Treatments were undertaken at the pre-veraison growth stage on Merlot vines. LR had no effect on fruit composition but levels of total anthocyanins and the flavonol quercetin-3-glucoside were enhanced in the wines. In contrast, CR increased sugar concentration and decreased titratable acidity of the must. While CR had no effect on wine anthocyanins, the proportion of anthocyanins as malvidin-3-glucosides, and also total phenolics in the wines were significantly increased. Relative to accepted indices of vine balance, the study vines were unbalanced with excessive shoot growth and dense canopies. A crop reduction of about 6.0 t/ha brought the capacity of the exposed leaf area into balance with that required to ripen fruit to optimum maturity and produce high quality wines.
- ©2012 by the American Society for Enology and Viticulture
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