Markus Keller, Garrett Stahl, Russell Smithyman, and Bhaskar Bondada*
*Washington State University, 2710 Crimson Way, Richland, WA 99354 (bbondada@wsu.edu)

A more time-efficient, less intensive, plant-based method that diversifies the irrigation scheduling toolkit is needed for irrigation scheduling. A portable leaf porometer measuring stomatal conductance to water vapor provides rapid, real-time, non-destructive data on current vine-water status, making it an appealing tool for irrigation scheduling. Three irrigation treatments were applied to a red (Merlot) and white (Chardonnay) cultivar of field grown grapevines (Vitis vinifera L.) over two growing seasons to evaluate the efficacy of porometry in determining the extent of water stress. These treatments included high irrigation (~100% ETc), moderate irrigation (~50% ETc), and low irrigation (~25% ETc). From full bloom through physiological maturity of grape berries, stomatal conductance and mid-day leaf water potential were recorded concurrently from a single leaf in each replication four to six days after the most recent irrigation. A significant positive linear relationship was observed between mid-day leaf water potential and stomatal conductance in all treatments of both cultivars. This indicates that stomatal conductance measured by a porometer can be used to detect water status in grapevines, and has potential as a tool for scheduling irrigation.

Funding Support: Northwest Center for Small Fruit Research (USDA)