Alternative Trellising Systems for Chardonnay and Merlot Vineyards in the Central Coast

The purpose of this study is to compare the performance of bilateral cordon trained, spur pruned Chardonnay and Merlot grapevines trellised to the vertically shoot positioned trellis system (VSP), the Smart-Henry trellis system (SH) and the Smart-Dyson trellis system (SD) in the Salinas Valley of California. In the first year of the study, VSP vines had less primary, lateral and total leaf area compared to SD and SH vines. Canopies oriented upward on both the SD and SH systems generally had more leaf area than canopies oriented downward. VSP vines had greater leaf layer numbers in the fruiting zone compared to SD and SH vines, and these treatments had greater amounts of sunlight in the fruit zone compared to the VSP treatment. Vine yield components were similar among the treatments in Chardonnay, while SH vines in Merlot produced significantly greater yields compared to the other treatments. In both cultivars, trends toward reduced yields for downward-oriented canopies compared to upward-oriented canopies were observed. Merlot fruit from downward-oriented shoots had lower berry weights, reduced rates of sugar accumulation and higher titratable acidity compared to fruit from upward-oriented shoots. Fruit on downward-oriented shoots on the SH system exhibited this trend more strongly than downward-oriented shoots on the SD system. At harvest, however, no significant difference in combined fruit (upper and lower canopies) soluble solids, titratable acidity and pH were observed among the treatments in either cultivar. Wine lots made from each treatment will be evaluated in late 1999.