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Serving: West

Defining drought and how to control it

California Association of Winegrape Growers GL0526-cawg-drought-vines.jpg
Grape vines are by their nature resilient and tolerant of drought.
WSU horticulturist Marcus Keller is studying its ramifications and considering responses.

Hardly a day goes by when drought isn’t the foremost topic of conversation in Western farm country.  There are those that have been devastatingly affected by it.  There are those trying to stave off its effects.  And there are those who are studying its ramifications and what to do about droughts as they pertain to vineyard impact.

“When we talk about that subject, we’re probably talking more about what we do not know than what we do know,” says horticulturist Marcus Keller, a life-long grape grower/winemaker/researcher from Washington State University, home to 30,000 acres of wine grapes.

“Drought can be defined in so many different ways,” Keller says. “We in the West are almost always in some kind of a drought because we have less rainfall during a growing season and water evaporates from the soil.  By itself, that fulfills the definition of drought because we have to irrigate or we won’t get by.  The question then becomes, do we have enough water available to irrigate?

“A real drought situation for grape growers is when the water gets shut off during certain parts of the growing season because there’s not enough available.  That’s already happened in California and Oregon last year and we came close to that happening in Washington.  In Southern Oregon last year, irrigation water was shut off completely starting August 1 leaving growers debating how to cope --- irrigate more quickly?  Irrigate less?  There’s just not enough information to deal with these kinds of situations.”

The typical reaction to that kind of water shut-off situation is to quickly pick fruit to ensure vines will survive to the next season, foregoing a crop in one year to save the plants for the following year.

“Problem is, we don’t know whether that’s even necessary,” he says. “I often advise growers to not act quickly, but to wait and see what happens.  Researchers will be looking into this question of early fruit removal benefits because right now even the experts aren’t sure.  Nobody knows if that standard approach is truly beneficial or not.”

Vines are drought-tolerant

Keller reminds: “We often forget that vines, grape vines in particular, are by nature quite drought-tolerant, very resilient.  Last year was perhaps the hottest summer we had on record here and we dug up a 10-year-old grapevine during 112 degree temperatures.  We re-potted it, but the leaves fell off and we were ready to toss it until it started to grow back.  It lost that year’s crop, but it proved grape vines are very good at surviving, perhaps not multiple consecutive years of drought, but one year of dry conditions.  If you stop irrigating a vineyard completely, it should be fine for that one year.”

As to ongoing climate change bringing extended periods of drought, “We often pretend it’s business-as-usual, but many growers are gradually adapting variety.  There’s a perceptive shift in varietal makeup in our grape regions and we’re a good example.  Fifty years ago, white and juice grapes were grown here, but the industry has shifted to red wine grapes --- a clear reflection of not just market, but the ability of a climate to ripen different types of grapes.

“Decades ago nobody would plant the current varieties we have and you’d have been considered a fool to do so.  Back then it was hybrid grapes and today there’s none left.  Now it’s all wine grapes from Europe as growers shift the makeup of their varieties.  In many cases, they’re moving to higher ground or cooler areas as well as adapting new irrigation and management practices like not removing as many leaves as they had in the past.”

TAGS: Weather
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