Pinpointing Vineyard Irrigation
Oregon grapegrowers install evapotranspiration monitor, eliminate guesswork
Typically, that’s done through methods ranging from visual monitoring to pressure bombs that extrapolate evapotranspiration data from bellwether vines across an entire vineyard.
Various services also exist that allow growers to estimate evapotranspiration rates for their particular locations based on general meteorological data.
But this Friday, Atlas Vineyard Management Inc. will install a system at Willakia vineyard east of Amity that measures the local vineyard climate, giving real-time local data to determine the needs of vines across a 10-acre block.
Developed by Tule Technologies Inc. of California, the system employs surface renewal analysis to measure moisture levels in layers of air above the vineyard, and matches that data with models of evapotranspiration rates prepared by USDA scientist Andrew McElrone and post-doctoral researcher Tom Shapland from the University of California, Davis.
The result is a more accurate picture of how vines are using water.
How it works
“To measure how much water the vines are using, surface renewal quantifies how much heat and water vapor the wind carries away from a 2- to 5-acre vineyard block,” Shapland explained in an article for Practical Winery & Vineyard earlier this year.
Tule’s system measures the moisture in different layers of air, or eddy fluxes, and extrapolates that across a 10-acre site to provide a more accurate read of local conditions than viticulturists previously enjoyed.
“Most of these devices are just connected to one or two vines,” explained Francisco Araujo, director of quality control and technical winegrowing operations for Atlas. “With one instrument we’re covering an exponentially larger area. We’re not extrapolating data from one or two vines, we’re measuring it over a large surface.”
Moreover, the local readings mean that growers aren’t relying on estimate-based conditions in a reference field that may be growing another crop such as alfalfa.
“We’re measuring directly the vineyard evapotranspiration as opposed to a reference evapotranspiration,” Araujo told Wines & Vines.
Atlas is piloting the system at vineyards in Napa and the Petaluma Gap, and the installation at Willakia (acquired earlier this year by Ste. Michelle Wine Estates) will be its third site and first in Oregon.
While it’s still too early to know how usage has changed, Araujo said there’s a lot less guesstimating going on with respect to irrigation needs.
“We’re seeing full canopy growth, and our growth targets have been met,” he said. “We don’t have that urgency to irrigate. We would otherwise be guessing, ‘Hey, it’s been a dry winter, what’s going on?’ So it’s really helping and giving us more information so we can decide.”
That information means one more tool in the kit of growers, who increasingly receive encouragement from extension workers to control water and regularly told of new methods to reduce and eliminate water use.
Okanagan growers attending the British Columbia Wine Grape Council meeting last year heard Mark Battany, an advisor to growers in San Luis Obispo and Santa Barbara counties with the University of California Cooperative Extension, explain how better climate information could help wean growers off sprinkler systems for frost control in favor of wind machines or better vineyard design.
While the impetus to manage water wisely is high in California, drier conditions this year promise to put water on everyone’s minds.
The latest report from Greg Jones, director of Southern Oregon University’s Division of Business, Communication, and the Environment in Ashland, notes that the accumulation of growing degree-days across the state through the end of May is up 26% to 68% above the normal for the period 1981-2010.
Meanwhile, precipitation is down by more than 20%.
The prospect of El Niño conditions emerging later this year promises drier, warmer conditions for the Pacific Northwest.