Issue link: https://read.dmtmag.com/i/657340
30 APRIL 1, 2016 Good Fruit Grower www.goodfruit.com For the past two years, Zhang and WSU viticulturist Dr. Markus Keller have been evaluating a selection of deficit irrigation strategies, including partial root-zone drying, to try to determine when and where water is most needed, while improving productivity and grape quality. They have focused on Chardonnay and Riesling grapes, which account for 75 percent of white wine production in Washington, applying several different irrigation strategies through the growing season for two years. They included treatments where no water stress was intended, different deficit irrigation strategies and partial root-zone drying. In all cases, soil water content was replenished after harvest and again before bud break if necessary. Overall, the partial root-zone drying showed some clear benefits relative to conventional deficit irrigation strategies, Zhang said. The berries were bigger and the yield was heavier, and when compared to strategies that employ no water stress, the technique reduced the amount of irrigation water applied. Partial root-zone drying resulted in similar water use compared to the other deficit irrigation trials, she said. "It's definitely a lot less than having no water stress," she said. "The idea is that by using this technique, you still reduce the amount of water usage, compared with not applying water stress at all. At the same time, it can give you less yield and berry size reduction compared with conventional deficit irrigation treatments." Ste. Michelle Wine Estates is collaborating on the research. Dr. Russell Smithyman, director of viticulture, said it's nice to have researchers' interest on irrigation in white varieties again. "It goes back to trying to get the best quality and water savings that we can in the vineyard," he said. "What we're seeing is that we're maybe applying more water than we need to for the quality purposes. And with the semi-defi- cit, the partial root-zone drying, the nice thing about that is they're showing there are similar types of wines and maybe even better wines produced under partial root-zone drying." Ste. Michelle completed irrigation research on Sau- vignon Blanc in the 1990s, Smithyman said. "There, our focus was to see if water deficit at that time could control canopy growth. Since then, we've come to this philosophy of trying to stylize wine in the vineyard by manipulating canopy growth through irrigation or water additions," he said. However, in the years since, most industry research has focused on red varieties. "Now we're seeing the right way of watering white varieties. We're working to be more efficient, maybe use less water and still have high quality," he said. "We're very excited about this work in whites, and we look for- ward to these final results." Another hypothesis the researchers want to study is whether partial root-zone drying will result in a slightly Yun Zhang 815 Wallace Way 2410 N. 4th Ave. 1155 S. Broadway 81156 Hwy 395 North Grandview, WA Pasco, WA Othello, WA Hermiston, OR 509-882-2060 509-547-1761 509-488-5623 541-567-6370 800-959-1535 800-595-1536 • Engineering & Planning • Technology Savvy • Precision Implementation • Dependable Products • Reliable Service "We own and manage the 60 acre C.C. Sullivan Farms near Pasco, and help with KP Sullivan Farms. Irrigation Specialists has helped us plan and provide irrigation produc ts to assist us with orchard upgrades and new planting projects as we grow. It is important to have accurate plotting of new orchard developments along with precise cost estimates. Irrigation Specialists has the background and expertise to provide us with data and budget information nescessary for planning and completion of our orchard projects" Shayne Richeson Irrigation Specialists Shayne Richeson Irrigation Specialists Conner Sullivan Conner Sullivan Cliint Sullivan Cliint Sullivan Conner and Clint Sullivan Owners and Managers C.C. Sullivan Farms