Influence of Canopy Density on the Performance of Vertically Shoot Positioned

The effects of leaf area density on the performance of vertically shoot positioned Chardonnay grapevines were examined over a three-year period. The experiment was established in 1996 in a mature, bilateral cordon trained and spur pruned vertically shoot-positioned Chardonnay vineyard located near Greenfield in the Salinas Valley. Primary shoot density was adjusted to 14, 28 or 40 shoots per vine (approximately 10 to 26 shoots per meter) following budbreak for three consecutive seasons (1996-1998). Cluster number and yield per vine increased with shoot density. Vines thinned to 14 shoots produced almost 5.4 tons per acre, while vines with 40 shoots produced about 11.7 tons per acre. Juice pH did not differ among the treatments, while berry weight, soluble solids and titratable acidity wee significantly lower for vines with 40 shoots compared to vines with 14 shoots. Total leaf area per vine and pruning weight increased with shoot density. Vines with 14 shoots had lower leaf layer numbers, greater numbers of canopy gaps, and higher percentages of exterior leaves and clusters, compared to vines with 28 and 40 shoots. Light penetration within the canopy declined as shoot number per vine increased. Despite dramatic effects on canopy density and light penetration, shoot density in 1997 had little effect on return fruitfulness during the course of this study. Little difference in wine quality among the treatments was found in 1998.