
The Walla Walla Valley experiences the most extreme climatic conditions among Oregon’s wine regions. While production systems have adapted, the shifting climate is producing more unpredictable and extreme conditions. Additionally, global climate change necessitates a shift towards more sustainable agricultural practices.
To address these challenges, the Oregon State University Extension Service horticulture program in Umatilla County has developed a multi-faceted applied research and Extension program focused on sustainability and climate resilience for local grape production.
By implementing kaolin clay trials and a cover crop project, OSU is helping local grape growers adapt to climate change and adopt sustainable practices.
In 2022, a pilot study was initiated to evaluate the use of kaolin clay in vineyards, inspired by its success in reducing heat stress and sunburn in local orchards. A local grower/winemaker hosted the trial in a Milton-Freewater vineyard. The pilot's success secured funding from the Agricultural Research Foundation to expand and continue the study from 2023 to 2025. In 2023, additional trials were established to fine-tune application methods and evaluate kaolin's effectiveness for insect control, wildfire smoke exposure and wine quality.
For the study, a grower and winemaker near Milton-Freewater agreed to host the kaolin project with OSU Extension in a commercial block of syrah, a regionally important cultivar. Kaolin was applied several times during the season to maintain canopy coverage. Vine stress, yield and fruit quality responses to kaolin were measured.
Most notably, the research found kaolin produced greater yields and fruit quality compared to the control plot, where kaolin wasn’t applied. Evidence also showed that kaolin reduced the impact of heat and light on vine leaf function. The grower produced wine from the study’s vineyard plot, which will be evaluated for future outreach to other wine grape growers in the Walla Walla Valley.
Another significant action was the launch of a cover crop research project from 2023 to 2026, funded by Western SARE (Sustainable Agriculture Research and Education), a program of the U.S. Department of Agriculture National Institute of Food and Agriculture.
This project aims to evaluate and increase the adoption of cover crops in local vineyards to improve soil health and grape quality. The project involves collaboration with several local growers, multiple research trials and planned educational components to address the unique challenges of using cover crops in this region.
The kaolin clay study's trial results have been shared with local, state and national audiences at events such as Walla Walla Grape Day and the American Society for Enology and Viticulture National Conference. The project concluded at the end of 2024, with results published in the American Journal of Enology and Viticulture.
The cover crop project is ongoing, with research and collaboration efforts aimed at enhancing the environmental sustainability of grape production in the Walla Walla Valley.
By implementing kaolin clay trials and a cover crop project, OSU is helping local grape growers adapt to climate change and adopt sustainable practices. These efforts enhance grape quality, soil health and overall vineyard resilience, benefiting the local community and beyond.