Effect of Crop Level and Crop Load on Growth, Yield, Must and Wine Composition, and Quality of Cabernet Sauvignon

Three crop load treatments by cluster thinning immediately after bloom were applied to a Cabernet Sauvignon vineyard located at Luzit in the Adulam region of Israel during five consecutive years. The crop load values expressed as the grape yield to pruning weight ratio varied between 4 in the severely thinned treatment and 10 in the unthinned treatment. Wine quality as determined by tasting was significantly higher in the unthinned as compared to the severely thinned treatment in two out of the five experimental years. The five year averages of the wine quality score did not vary significantly. The pruning weight was negatively rank correlated with crop level and crop load, and positively with the harvest delay. Potassium leaf, must and wine content was negatively rank correlated with crop load, crop level, must malic acid and wine color, ash and tartaric acid content. Comparison of these results with those obtained earlier with Carignane lead the authors to suggest that crop load values above 10 have a negative effect on wine quality whereas no significant effect is apparent with values lower than 10.