Water Use of Wine Grapes In the Temecula Grape Region of California
The second of a four-year study to determine vine water use and effects of various irrigation amounts imposed either at bloom or veraison in the Temecula region was completed during the 1998-growing season. Calculated vine water use (ETC) from budbreak, 9 March, to the end of the growing season, 26 October, was 23.9 inches (1,399 gal. per vine). Applied water from the first irrigation (28 April) to harvest was 17.2 inches (906 gal. per vine). A measure of vine water status (midday leaf water potential) indicated that close to harvest, our estimates of full vine water were pretty much on schedule. The application of differing amounts of water and time the treatments were imposed affected berry size and composition. Irrigation applications at the lowest amounts (25%of estimated ETC) reduced berry size by 14%when the treatments were imposed at bloom but less so when they were imposed at veraison. Maximum size resulted from irrigation amounts at 75 to 100%of estimated full vine water use. There were differences among irrigation treatments with regard to berry composition (soluble solids, pH and titratable acidity [TA]). Higher soluble solids were obtained as irrigation amounts decreased and higher TA as irrigation amounts increased. There was a significant interaction between irrigation amounts and time of treatment imposition with regard to yield. Yield averaged across all treatments was approximately 6.2 tons per acre. Pruning weights increased significantly as the amount of water applied increased. Wines were made by the Calloway winery in 1998 and are currently being assessed by winemakers in the Temecula Valley.