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New study confirms less water usage in vineyard can result in better grapes

As local farmers well know, Mother Nature can be cruel in administering her gifts.

That was the case on the night of Sept. 11 when the crew over at Emeritus Vineyards in Sebastopol felt raindrops as they picked the pinot noir grapes to go into the winery’s premium wine.

While any rain is appreciated during an exceptional regional drought, the precipitation came an inopportune time for the winery that would wrap up its harvest just a week later, said Riggs Lokka, assistant vineyard manager.

“All of the sudden at 1:15 in the morning, it just dumped,” Lokka recalled.

The episode underscored the conditions vineyard managers are operating under: their industry is facing a prolonged era of water scarcity in which growers don’t want to put one more drop of water on their vines than needed.

Local agriculture’s water usage has come under increasing scrutiny. Three of Sonoma County’s 14 groundwater basins are subject to increased monitoring and regulation. Those areas are mandated to be sustainable within 20 years, which means to have no significant drop in water tables on a year-over-year basis. In addition, state regulators so far this year have ordered more than 1,800 water right holders in the Russian River watershed to stop water diversions unless they obtain waivers.

But the oversight comes as academic research is showing that less water is better for the grape crop, which was valued at $357 million in 2020 in Sonoma County. It can even improve grape quality. A UC Davis study released earlier this month found that grape growers in our region can use less water on vines without affecting crop yields or quality.

The research published in the journal Frontiers in Plant Science found that vineyards can use 50% of the irrigation water normally used by without degrading the fruit’s flavor, color and sugar content.

The researchers focused on cabernet sauvignon at a research vineyard in Napa Valley over two growing seasons: a rainy one in 2019 and a hyper-arid one in 2020. The team examined the amount of water lost to the atmosphere from the vineyard system based on canopy size. The weekly tests used irrigation to replace 25%, 50% and 100% of what had been lost by the crop because of the evapotranspiration, which is the process by which water evaporates from the vine as well as the soil.

“It is a significant finding,” said Kaan Kurtural, a UC Davis professor of viticulture and enology who led the study. “We don’t necessarily have to increase the amount of water supplied to grapevines.”

There has been a constant debate for years over whether vineyards locally should move to dry farming, where natural rainfall, not irrigation, is used to produce a crop. Though some local vineyards are dry farmed, Kurtural said doing such a process would not be financially viable for the overall industry in the Golden State.

“In California, it’s not going to be economically feasible for our system,” he said. “Our system is making the most yield with lowest cost.”

Even without adopting dry farming practices, many vineyards on the North Coast, the most prized growing region in the United States, are using much less water because of water scarcity as well as the benefits to grape quality, said Mark Greenspan, a Windsor consultant who holds a doctorate in agricultural engineering.

“The people we work with anyway have done a good job minimizing irrigation,” Greenspan said. ”And that is mostly delaying irrigation … in many cases we haven’t seen irrigation at all.”

Joe Dutton, co-owner of his family’s Dutton Ranch in the Green Valley near Sebastopol, said about a third of their 1,200-acre vineyard is dry farmed. The farm has a mix of wells and reservoirs to draw water for irrigation. Dutton noted there was little water from the lack of winter rains to irrigate with this past year.

“We’re west county out here where water has been scarce anyway,” Dutton said. “We have learned to farm with minimal water our entire life. When you get west of Highway 116, you get into pretty scarce water situations.”

Greenspan tries to help his clients hold off watering in the growing season as long as they can. Viticultural areas closer to the Pacific Ocean and San Pablo Bay are more suited to use less irrigation than those more inland.

But this year, some vineyards that would typically be irrigated in early August received water in mid-July, he said. Some of those farms would likely run out of water before harvest.

One key determinant on deciding on whether to irrigate is soil moisture, Greenspan said. “In my mind, it’s really the soil moisture that has allowed us to precisely apply irrigation and prevent excess irrigation,” he said. “To me, that is the best tool and always will be.”

Lokka can easily access his soil moisture measurements on his smartphone through an app that is linked with sensors to software provided by Agrology, a startup working with a few vineyards across Napa, Sonoma and Mendocino counties. The company, which has offices in Sonoma County and Virginia, aims help vineyards monitor not only irrigation but also smoke levels to give farmers a better understanding of how susceptible their crop can be to smoke taint.

“I can see my soil moisture level. They (the software) tap into the irrigation system. They can see exactly how you turn on water and when you don't turn on water,” said Lokka, who added that he especially values the smoke data as smoke taint within the local crop has been an emerging issue in the past few years given how its affects quality.

Lokka said he typically uses water only to administer liquid fertilizer for the upcoming season, which he did some this week, and for frost protection in low-lying areas with overhead sprinklers. But the drought did force an emergency irrigation earlier this year.

Emeritus was forced to irrigate a few pockets in their vineyard around the Fourth of July when the heat became excessive. “We just gave them a quick shot,” he said. “They maybe got 2 gallons of water per vine.”

You can reach Staff Writer Bill Swindell at 521-5223 or bill.swindell@pressdemocrat.com. On Twitter @BillSwindell.

Bill Swindell

Business, Beer and Wine, The Press Democrat  

In the North Coast, we are surrounded by hundreds of wineries along with some of the best breweries, cidermakers and distillers. These industries produce an abundance of drinks as well as good stories – and those are what I’m interested in writing. I also keep my eye on our growing cannabis industry and other agricultural crops, which have provided the backbone for our food-and-wine culture for generations.

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