Argentinean Grad Student Puts Irrigation Research to the Test
When Daniela Romero heard WSU’s Markus Keller talking about irrigation during grape ripening, her curiosity was piqued. After all, applying water close to harvest time was simply not done.
Keller was teaching a grape physiology course at the Universidad Nacional de Cuyo in Mendoza, deep in the heart of Argentina’s wine country. Romero is a graduate student at the university and she asked if she could join Keller’s research team to learn more about his tradition-defying research.
“Keller’s research is important to the wine industry because it will influence the way growers add water to their vineyards. In most of the world’s wine regions, irrigation during grape ripening is thought to dilute the sugars in grapes — but this belief does not have any scientific foundation,” Romero said.
As Keller pointed out, “The European wine industries and their many regulators have it all figured out: irrigation during grapes’ critical ripening period is generally a bad thing and must be strictly regulated.”
A quote from the International Organization for Biological and Integrated Control in their 1999 Guidelines for Integrated Production of Grapes illustrates Keller’s point: “Irrigation of vines for wine production will not be applied after véraison or highly restricted by the regional guidelines in order to guarantee the good quality of the wine.”
“The tacit assumption is that irrigation boosts berry size and dilutes the quality-impact components of the grapes,” Keller said. “So pervasive is this argument that, even in the New World, many wineries encourage growers to withhold irrigation water during fruit ripening to avoid any perceived adverse effects.”
Keller and former graduate student Marco Biondi put the assumptions to the test – with startling results that fly in the face of viticultural tradition.
“We proved that berries are not hydraulically isolated during ripening,” Biondi said in a 2008 interview. Indeed, Biondi’s experiments show that berries absorb water in a variety of ways, including through the skin and not just through the root system, as commonly believed.
“Late season irrigation doesn’t decrease Brix,” Biondi said, “but irrigation does increase photosynthesis in the leaves, and photosynthesis in turn increases Brix.”
“In other words,” said Keller, “irrigation accelerated ripening!”
Now, Romero is putting Keller and Biondi’s results to the test in a series of field-based experiments in Argentina.
“This is important, for a number of reasons,” Keller said. Better knowledge of the potential contribution of late-season irrigation and water stress to variations in berry size will lay the foundation for better vineyard irrigation management. It also will end the long-standing debates whether irrigation close to harvest will dilute grape sugar and flavors, or whether heavy irrigation may increase berry volume in juice grapes.
Such knowledge is needed to avoid excessive water application or deficit close to fruit maturity, which is potentially detrimental to fruit quality, canopy health, cold acclimation, and vine longevity. It will also improve efforts to estimate yield and make yield prediction more accurate and reliable. This will improve harvest planning, grape and wine quality management, and marketing to ensure a consistent, high-quality supply of fruit for both domestic and export markets.
Large wine companies have already begun to modify their irrigation practices based on results from this study, Keller said, because conservative estimates suggest that the strategy of increasing water supply close to harvest may prevent a greater than five percent yield loss. For Washington alone this would amount to increased returns to growers in the order of $6 million per year (assuming an average crop of 4 tons/acre @ $1000/ton on 30,000 acres) and almost $2 million per year to juice grape growers (assuming an average crop of 10 tons/acre @ $150/ton on 26,000 acres).
In the mean time, summer is fast approaching in the southern hemisphere and Romero’s experiments should yield results soon. When they do, you’ll read about them here, in Voice of the Vine.
Read an article by Markus Keller in the Spring, 2008 issue of the WSU Wine and Grape Research and Extension Newsletter. In the article, Keller makes some recommendations for growers.
Read our interview with Marco Biondi in the Feb. 2008 issue of Voice of the Vine.
Grapevine Cold Hardiness Evaluation Continues
Cold damage to grapevines continues to threaten Washington’s grape growers.
As the record low temperatures in early October demonstrate, growers can never be sure when a cold event will occur nor how severe it will be.
This is why the WSU viticulture research team, led by Markus Keller, continue again this year to collect data from buds and wood pieces from a range of grape varieties in order to determine “critical” temperatures (the temperatures at which the tissues freeze and are killed) for each variety.
Because the temperature at which the buds and canes freeze depends on the variety and fluctuates throughout the winter, such information is important to growers needing to make frost-protection decisions.
The latest cold-hardiness data are posted each week on WSU’s wine science Web site (http://bit.ly/3j0Ces) from early October through April.
In addition to Washington’s “standard” varieties, the WSU team also evaluates emerging varieties of current or potential interest to the industry. Web site visitors may click on a variety name, which will open a new window with the seasonal hardiness graph for that variety along with the temperature profile. Growers may use these graphs to follow seasonal trends and forecast approximate hardiness levels based on current temperatures at their site.
The service is funded by WSU, the Washington Association of Wine Grape Growers through the Washington Wine Industry Foundation and the Washington State Concord Grape Research Council.
Visit the Grape Cold Hardiness Web site: http://bit.ly/3j0Ces. The site has year-round value for grape growers, including information on Powdery Mildew, precipitation, growing degree days, and evapotraspiration.
Want the scientific low down on how Keller’s team is collecting cold-hardiness data? Fire up your browser and visit the American Journal of Enology and Viticulture to download the paper by Mills, Ferguson and Keller: http://tinyurl.com/63q5te.
Raise a Glass, Fund a Scholarship
Chateau Ste. Michelle Winery has for the second year teamed up restaurants around the state to raise funds for the WSU Viticulture and Enology Program. In its first year the “Raise a Glass, Fund a Scholarship” program raised $40,000.
This year, Ste. Michelle has expanded the program to Oregon, partnering with Erath Winery and Oregon restaurants to also raise funds for Oregon State University’s Agricultural Sciences program. As a result, nearly 200 restaurants in the two states are participating this year.
The way the program works is that Chateau Ste. Michelle and Erath will donate a portion of their wine sales through participating restaurants from now through the end of December to fund scholarships, research, and equipment for the wine science programs.
“Raise a Glass, Fund a Scholarship” is being done in conjunction with the annual “Celebrate Washington Wine” gala black tie dinner and auction held at Chateau Ste. Michelle in Woodinville to support the WSU V&E program. The ninth annual auction will be held on Saturday, January 30.
You can also support the program by attending the Auction and Gala on January 30 or by participating in the online auction that will get underway on Nov. 16. Please visit the www.wineauction.wsu.edu to register or to learn more about the auction.
Ladies and Gentleman, Start Your Bidding!
A stunning three-year vertical of 1.5-liter magnums commemorating Washington State University’s annual “A Celebration of Washington Wines” gala and auction is now available on the online auction block.
Bidding opened this week on the commemorative set of three etched and hand-painted bottles featuring the WSU Cougar-head logo valued at $750. The bidding opened at $250.
The vertical features 2004, 2005 and 2006 commemorative bottles filled with Chateau Ste. Michelle Cold Creek Vineyard Columbia Valley Cabernet Sauvignon.
The 2004 bottle features the 2000 vintage of the wine, the 2005 bottle the 2001 vintage, and the 2006 bottle holds the 2002 vintage.
There is only one three-year vertical remaining, so this is the last chance to obtain the set. The bidding will close on November 30.
The online auction is a new feature of the annual “Celebrate Washington Wine” gala dinner and auction that benefits the WSU Viticulture and Enology program. The gala is slated for January 30 at Chateau Ste. Michelle Winery in Woodinville.