Effect of Sprinkler Cooling of Grapevines on Fruit Growth and Composition

Abstract

9Cardinal,9 9Carignane,9 and 9White Riesling9 vines, grown in 5-gallon containers at Davis, California, were sprinkled sequentially for different periods when air temperature exceeded 86°F during the periods from bloom to midway between veraison and fruit maturity (14 to 18°Brix), and from veraison (10-13°Brix) to fruit maturity. These cultivars were also sprinkled continuously when air temperature exceeded 86°F between bloom and fruit maturity (20 to 23°Brix). Leaf and fruit temperatures were usually 10 to 40°F lower on sprinkled vines than on unsprinkled vines. All sprinkling treatments increased the fresh and dry weights of berries from each cultivar. Sprinkling during the period from bloom to shortly after veraison was more effective in increasing berry weight and size than was sprinkling during the postveraison period, and continuously sprinkled fruits were generally larger than intermittently sprinkled fruits. Sprinkling between bloom and shortly after veraison had little effect on the level of total soluble solids; however, fruit maturity was delayed in continuously sprinkled Cardinal and 9Carignane9 during the last 2 to 3 weeks before final harvest. Only fruits sprinkled continuously from bloom to berry ripeness had significantly higher levels of titratable acidity anad malate, and lower pH, than did unsprinkled fruits at that time. The levels of these substances in fruits from vines sprinkled intermittently were generally intermediate between those of the continuous and those of the unsprinkled berries. All sprinkling treatments greatly increased coloration of 9Cardinal9 fruits, but only slightly increased coloration of 9Carignane9 berries, compared to unsprinkled fruits. The practicality of using overhead sprinklers to cool vineyards and improve grape quality under vineyard conditions remains to be shown.