Published in Practical Winery & Vineyard
By Melissa Hansen & Joelle Martinez
October 2020
Winegrape water management has witnessed many breakthroughs during the last two decades, from deficit irrigation optimization to vine and berry water relation studies. Most recently, scientists have looked to optimize irrigation management for red and white varieties. Beside the emphasis on the different berry composition needed in reds and whites, many differences remain at the variety level. Such differences are present even when the vines are grown side by side.
The classic tale offered by past research describes winegrape varieties as isohydric, or pessimists, and anisohydric, or optimists.1 It is thought that a pessimist variety, such as Grenache, maintains a high leaf water potential during soil drying by closing stomata and shutting down photosynthesis. The opposite can be said about an optimist variety, such as Syrah, that keeps stomata open but drops its water potential to low levels while maintaining photosynthesis.
The Washington State Wine Commission, a state agency that represents all winegrape growers and wineries in Washington state, in conjunction with Washington State University (WSU) and the Auction of Washington Wines, has funded a four-year research project to reduce the guesswork in water management when different winegrape varieties are grown.
By following the water stress responses of 18 different winegrape varieties grown on their own roots side by side in a WSU experimental vineyard in Prosser, the research was able to better elucidate stress behavior classification of own-rooted winegrape varieties. It was shown that the varietal response to water stress cannot be put into two classes. Moreover, the results generated preliminary recommendations on a monitoring approach that growers could adopt if they want to optimize irrigation management of the differences seen in their vineyards.
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