Water Use of Wine Grapes Along the Central Coast of California – Validation

AVF Proj. ID: 9747 / /Cat.: ,
Primary Investigator(s): Larry E. Williams, Larry Bettiga, Mary Bianchiby

A study was initiated in two vineyards along the central coast of California to determine the applicability of crop coefficients and deficit irrigation factors established in a Chardonnay vineyard located in the Carneros district of Napa Valley at other locations. Since the amount of money received from the American Vineyard Foundation was only 44%of that requested, data were only collected in a Chardonnay vineyard located in Monterey County and a Cabernet Sauvignon vineyard east of Paso Robles. No data were collected at the other proposed site (a Chardonnay vineyard located in the Edna Valley) nor were data collected in all blocks of the two above cited vineyards. Irrigation treatments began on 6 May in the Chardonnay vineyard with a total of 305 gallons of water (10.2 inches) applied per vine up to harvest (Oct 1) for those irrigated at 100%of estimated full ET. Irrigation treatments commenced 12 June at the Paso Robles site with a total of 321 gallons applied per vine to those receiving 100%of estimated full ET. Maximum berry weight was obtained at approximately the full ET treatments at both locations. Application of water at amounts greater than full ET did not increase berry size. There were no significant effects of irrigation treatments on soluble solids or pH at the Monterey site. Titratable acidity increased as applied water increased at that site. As applied water increased at the Paso Robles site, soluble solids decreased. There were no significant effects of irrigation treatments on titratable acidity at Paso Robles. Maximum yields at the Monterey site were obtained at the 125%irrigation treatment when averaged across rootstocks. This was probably due to the fact that the vines at that site were inadvertently stressed early in the season (during bloom/berry set). Maximum yields at the Paso Robles site were obtained at the 50%irrigation treatment for two of the rootstocks, at the 75%treatment for another and at 100%of estimated full ET for the remaining two rootstocks. These results were probably due to the fact that the treatments were not imposed at the Paso Robles site until after berry set had occurred during the 1997 growing season. Wine lots were not made after harvest in 1997.