Issue link: https://read.dmtmag.com/i/705606
6 0 V I N E YA R D & W I N E RY M A N A G E M E N T | J u l y - A u g 2 016 w w w. v w m m e d i a . c o m BY MELISSA HANSEN, WASHINGTON STATE WINE + The tradition of withholding pre-harvest irrigation from vines can be damaging to vineyards. + Washington State University research proves that using drip irrigation post-veraison will not increase berry size. + The research also shows drip irrigation doesn't dilute sugars and helps avoid berry dehydration. + As a result of the research, many Washington winemakers have changed their irrigation mindset. AT A GLANCE he European-held wine dilu- tion theory is so entrenched in the wine industry that many U.S. winemakers also believe it's best not to irrigate wine grapes at all before harvest. It's a theory not supported by science and one that can have detrimental effects on a grower's bottom line. The combination of no pre- harvest irrigation and a prolonged fruit ripening period can have nega- tive consequences for wine grape growers, especially those in arid climates. In places like Washington State, with scant precipitation in the fall, withholding irrigation after veraison not only has potential for yield loss but, more important, may leave soils dry going into winter, a recipe for root and vine damage if cold winter temperatures hit. R e s e a r c h s u p p o r t e d b y t h e Washington State Wine Commis- sion and the Northwest Center for Small Fruits Research has brought science into the irrigation-dilution concept to help Washington's wine industry keep vines healthy and avoid millions of dollars in yield losses — all while maintaining wine quality. Industry officials have esti- mated that preventing 5% yield Rethinking Post-Veraison Irrigation Science disproves centuries-old tradition of withholding pre-harvest irrigation from vines. Electronic sensors measured changes in berry diameter from pre-veraison to harvest and from water stress and re-watering. (Photo credit: Washington State University)