WSS irrigation

Alexander Levin, viticulturist and assistant professor, makes a measurement using a pressure chamber — a tool that growers can use to determine how wet or dry their vines are, which ultimately helps them decide when to irrigate. Sort of like measuring the vine’s “blood pressure.”

Originally, Alexander Levin, viticulturist and assistant professor in Oregon State University’s Department of Horticulture, got into the industry to become a wine maker.

During an internship, however, he became more interested in the vineyard side of the business. He went back to school in 2012 and specialized in irrigation.

Irrigation is a crucial part of any agricultural enterprise, but when it comes to vineyards standard irrigation methods don’t necessarily transfer.

Levin said irrigation is a critical part of the winery business, especially in the Willamette Valley, but farmers may not need to apply all of the water they think they need.

The biggest difference between irrigating field crops and grapes is there’s a discontinuous canopy with grapes. Instead of a lawn where the entire surface area is covered by leaves, in a vineyards only narrow lines are covered.

“You need to account for that — not covering the whole surface of land because it’s tight in rows with trellises,” he said. “You still need to irrigate, but you can be more conservative with amounts.”

When it comes to when and how much to irrigate, he said farmers are still relying on visual symptoms because it’s the cheapest and easiest way.

“The plant is wilting; put water on it,” he said. “Plant growth is one of the most sensitive physiological processes to water stress. Visual symptoms can be diagnostic. However, the challenge is things are interpreted as soil stress could be due to something else.”

Instead, he recommends using an integrated irrigation water management process to keep grapes hydrated. This includes scientific methods like water budgeting, measuring soil moisture and using plant-based methods.

Water budgeting is similar to balancing a checkbook, where the amount of water to be applied is calculated as the balance between the amount of water held in the soil root zone, and the estimated amount of water used by the crop over a given period of time.

Estimates of crop water use can be made from local or regional weather data and crop growth stage or canopy size.

Levin said that although he is a proponent of using plant-based methods because it’s the biggest indicator, the more scientific the strategy — the more labor intensive and costly it gets.

“When I talk to growers, everyone wants to do the most basic things and processes,” he said. “I find the trouble is when (farmers) don’t have a plan or don’t stick to a plan.”

However, Levin found that many farmers prefer science-based tools to actively checking their plants.

He said that even while using scientific methods it’s still important to look at the plant and assess its needs that way as well.

“(Farmers) want someone to tell them when to turn the water on and for how long, but it’s not that simple,” he said.

Overall, whether to irrigate is an economic decision with costs and benefits. Levin also added that he can’t decide for the farmer which method is best. His advice, however, is to create an irrigation plan and stick with it.

“Growers don’t irrigate when plants are stressed,” he said. “They irrigate when they’re stressed.”

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