Final Report – Funding Cycles 2020 – 2024 (four year project)

Principal Investigator: Markus Keller, Washington State University, Prosser

Telephone: 509- 786-9263

Co-PI: Joelle Martinez, Charles Obiero, Washington State University, Prosser

Cooperators: Gregory Gambetta, University of Bordeaux, France, and Jim Holmes, Ciel du Cheval Vineyard, Benton City, WA

Summary: Irrigation management strategies have not evolved in parallel with the varietal diversification of Washington’s wine industry. The main approach for water application is a regulated deficit irrigation program that is more-or-less customized to fit either red or white varieties. However, growers often report that some varieties tend to show peculiar behaviors, making irrigation management somewhat ambiguous. In the past, grape varieties have been grouped into “pessimists” (called isohydric) and “optimists (called anisohydric), but our recent research has shown that this categorization is overly simplistic. This challenges the current one-size-fits-all approach to deficit irrigation, and partly explains why irrigation management can sometimes have unpredictable outcomes. The present study addresses these knowledge gaps by comparing varietal behavior across regions with disparate climates and soils, namely Washington’s Yakima Valley and Red Mountain AVAs and France’s Bordeaux region. This will help us to determine the extent to which differences in behavior are driven by genotype (variety) versus environment (vineyard site and growing season). Such information is essential to develop variety- and site-specific irrigation management strategies. Thus, the research outcome will provide growers with a pathway to improve grape quality using enhanced knowledge-based irrigation scheduling.

Irrigation // Viticulture //