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HoytShepston_Monthly09 10/31/08 4:44 PM tween variety and rootstock choices.) De- pending on the year, this will occur ahead of veraison in warm climates and possibly after veraison in cooler climates. Once you start to irrigate, you would use your measured crop coefficient to apply water as a percentage of reference evapo- transpiration. Most growers using this sys- tem will irrigate right up until harvest. How often to irrigate There is still some debate about how many times per week to irrigate. Evapotranspira- tion data will give you an idea how much to water per week. Then the question be- comes, how many applications should you make to apply this amount? If the water- holding capacity of the soil is limited, more frequent irrigations make sense since you could potentially apply more water than the soil can hold if you only irrigate once per week. The water that can't be held by the soil will pass through the soil pro- file, often taking plant nutrients with it. If vines are young and actively growing, more frequent applications keep the vines from stressing. If you are anticipating hot weather, it is also a good idea to irrigate in advance of the heat, perhaps even irrigat- ing extra to insure that there are adequate moisture reserves for the vines to cope with greater water stress. On soils with good water-holding capacity and deep rooting, you can irrigate less frequently. Conclusions Irrigation is another tool in the toolbox to improve winegrape quality. Grapevines are quite efficient at finding moisture in the soil—and compared to many other crops, they sip rather than gulp water. Since wa- ter is an important resource that is expen- sive to apply to vines, it makes sense to use this input as carefully as possible to grow the best fruit possible. Glenn McGourty is the UC Cooperative Ex- tension winegrowing and plant science advisor for Lake and Mendocino counties. He also tends a 1-acre vineyard of the aromatic Italian wine- grape variety Arneis on his property along the Russian River near Ukiah, Calif. To comment on this column, e-mail edit@winesandvines.com. Additional Resources GovtLiaison_Dir08 11/29/07 2:00 PM P GRAPE GRO WING APPROVALS TTB LABEL Low per-label costs Gov't. Liaison Negotiations or Footwork Reasonable Hourly Rates TRADEMARK SEARCHES As Low as $185 Your trade names or designs are searched at the U.S. Patent Office to help establish valuable ownership Over 100 years' total staff experience handling every government liaison need for industry. or avoid costly legal liability. Phone or write for details. Castoro_Nov08 10/8/08 1:54 PM Page 1 Phone: (703) 524-8200 Fax: 525-8451 TOLL-FREE 1-800-642-6564 Major Credit Cards Accepted www.trademarkinfo.com Since 1957 200 N. Glebe Rd., Suite 321 Arlington, Virginia 22203 You know how good your Zinfandel is... Promote your wines to leading Zinfandel enthusiasts and extend your winery's relationship in the market. Join Us! We are champions of Zinfandel— America's Heritage Wine Become part of our proud legacy • VELCORIN DOSING NOW AVAILABLE! • Bottle cleaning, sparging & gravity filling • Vacuum corking & multiple head corkers • All types of capsules including SCREW CAP • Single or dual web PS labeling • NEW – 187ml bottling 1. Read Terry Prichard's various publications about RDI and other aspects of winegrape irrigation at http://ucanr.org/sites/CE_San_ Joaquin/Custom_Program/Publications_Avail- able_for_Download/. 2. Visit Natural Resource Conservation Service Soils for GIS-based information about your vineyard's soils: http://soils.usda.gov/survey/. zinfandel.org • 530-274-4900 Zinfandel Advocates & Producers is a 501(c)(3) non-profit organization. ZAP is dedicated to advancing public • 20 years of hands-on bottling experience • Supported by a winery • Experienced bottling line technicians • Technical support for bottling prep & packaging • Competitive prices knowledge of and appreciation for American Zinfandel and its unique place in our culture and history. Wines & Vines AUGUsT 2011 65