Date: 31 January 2013

Title: Field Validation of a Vineyard Site-Selection Tool for Washington State

Principal Investigator: Michelle Moyer, Assistant Professor, Viticulture Extension Specialist, WSU-Prosser,
Address: 24106 N. Bunn Rd., Prosser, WA 99350.
Phone: 509-786-9234, Email:

Cooperators: Joan Davenport, Professor, WSU-Prosser,
Address: 24106 N. Bunn Rd., Prosser, WA 99350.
Phone: 509-786-9384; Email:
Role: Mapping and site selection tool support.

WSU Project Number: 3357-4377

Project Summary:

Between 2011 and 2012, multiple vineyard locations in Washington were used for ground truthing the WSU Vineyard Site Selection Model. American Viticultural Areas represented in the validation process were: Red Mountain, Walla Walla, Columbia Gorge/Hood River, and Lake Chelan, in addition to locations outside of AVA boundaries. These sites were GPS-mapped and the locations were assessed using the model, to determine site suitability for grape production. Prior to model ranking, manual assessments of most sites were conducted, including data collection regarding planting history, production statistics, perceived fruit quality, frequency of damaging weather events (particularly frosts and freezes), and frequency of disease outbreaks. These manual assessments were compared to the model ranks to determine where the model was performing well and where potential improvements could be made. Overall, the model was able to accurately assess in-season conditions that would either be favorable or detrimental to grape production (such as heat accumulation and frost free days). In addition, it provided excellent insight into site soil conditions and situations such as excess or insufficient drainage. However, the model (which is a mathematical calculation that combines multiple factors in a ranked form, to determine overall suitability) in its current form is not able to predict the likelihood of dormant freezing events, a critical factor in site selection in eastern Washington. As such, while the model itself does not appear to be that useful, the work of database collation and individual parameter ranking that was necessary to develop the model has proven to be a very useful extension tool for off-location evaluation. As such, the current model should not be used for site evaluation, but the remaining databases can be. In addition, this tool should be referred to as a “site evaluation” tool rather than “site selection”, due to the varied vineyard management practices that can be used to manipulate locations to suit production needs.

Read more by downloading the report article above.

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