Influence of Canopy Density on the Performance of Vertically Shoot Positioned Grapevines in the Central Coast
The purpose of this study is to examine the effects of leaf area density on the performance of vertically shoot positioned Chardonnay grapevines. 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 in both 1996 and 1997. In the second year of the study (1997), cluster number and yield per vine increased with shoot density. Vines thinned to 14 shoots produced almost 4.5 tons per acre, while vines with 40 shoots produced about 7.5 tons per acre. Fruit soluble solids and pH did not differ significantly among the treatments, while berry weight was significantly lower and titratable acidity significantly higher, respectively, for vines with 40 and 14 shoots. Total leaf area per vine increased with shoot density, while pruning weight was lowest for vines with 14 shoots. 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 1996 had little effect on return fruitfulness in 1997.