WATER-USE OF VITIS-VINIFERA GRAPES IN WASHINGTON

A long-term research project was initiated in 1983 on a 1.2 ha trickle -irrigated Vitis vinifera vineyard to address water management of Whit e Riesling (WR), Chenin blanc (CB), and Cabernet Sauvignon (CS) grapes in central Washington. Six large drainage lysimeters, two per cultiva r, were installed to monitor crop water use. Each lysimeter contained two vines. Vines were balance pruned and shoot-thinned to achieve an e quivalent crop level of about 15 Mg/ha of grapes. Analyses showed that published crop coefficients (ET.) for mature grapes greatly overestim ate water use early and late in the season for Washington conditions a lthough peak crop coefficients of about 0.8-0.9 were similar. Annual c rop water use for all three cultivars ranged from 130 mm for one-year- old vines in 1985 to as much as 540 mm for mature vines in 1990. The a verage crop water use for small, young vines (1985-86) was about 146 m m/yr, and from 1987-90 for mature plants it was about 417 mm/yr for al l three cultivars.