Ice Makes Nice

California wine grape grower finds microsprinklers are the best way to cut water use while still protecting vineyards from frost.

By David  Eddy, Western Editor

Robert Carrillo had a problem.  The Fetzer/Dobson Vineyards he manages at the north end of California’s Sacramento Valley are located at an elevation of 2700 feet, so winters are fraught with frost hazards.  He needed a sprinkler system to coat the vines with ice, providing a protective blanket from the bitter cold.

When you have a high-dollar crop such as good Chardonnay, just one degree can make a big difference, says Greg Jorgensen, field research manager of the Center for Irrigation Technology at California State University-Fresno.  “It can certainly mean the difference between a profitable crop and no crop,” he says.

The vines will generally be safe at the freezing point of 32°F, says Jorgensen, which is what makes a sprinkler frost protection program effective.  “We want wet ice,” he says.  “We want it to keep freezing.”

As an alternative, a grower could use heaters.  But because you need 20 to 40 per acre, they aren’t used in many areas, says Jorgensen.  “Just because of the cost of the diesel fuel alone,” he continues.  “Maybe in $40-a-bottle vineyards, but for the rest of the world I can’t imagine it.”

Precious Commodity
So like most growers, Carrillo had to use sprinklers.  But he didn’t have access to that much water.  In fact there were times when at peak usage – sometimes running the system every day for two to three weeks to minimize frost damage – that he came close to depleting his water supply and putting the crop in jeopardy.

He decided to conduct an experiment to determine the best method of protecting the grapes in the winter months without leaving his reservoir dry.  In March 1998, he installed a microsprinkler system manufactured by Wade Rain of Fresno, CA, called the Pulsator.  He decided on the Pulsator because it uses just 15 gallons per acre, per minute compared to the system he had been employing which used 55 to 60 gallons per acre, per minute.

He and a consultant, Bill Faggard, who used to manage the vineyards, hooked the system up to a garden hose.  They were skeptical, to put it mildly.  “I see a thin little stream of water and I think, ‘There’s no way this will protect us,’” Carrillo recalled.

They had committed two, 1/2-acre blocks of Chardonnay wine grapes for the experiment, an area of the vineyard which had sustained some of the worst frost damage in the past.  They installed the Pulsators at the lower end of the block set for 3 gallons per minute per unit.  The top of the block had units that used 6 gallons per minute and the center of the block remained protected by conventional overhead sprinklers.

The Easter Freeze
The lowest temperature recorded that growing season, which begins in March, was 25°F.  All three systems came through with flying colors, and there was no significant difference in crop loads or pruning weights in the three areas.  But the next year was a different story.  “We did not know what kind of frost we were up against that year,” says Carrillo.

Frost protection began on March 19, 1999.  The frost continued and got so bad that the overhead sprinklers would freeze up and stop turning.  On April 9, the temperatures dropped to 21.5°F.  They had to keep the water running all of the time.  “There was lots of ice,” says Carrillo.  “It was amazing.”

The tops of the blocks, where the high-flow sprinklers were installed, were protected best, with no noticeable frost damage.  The microsprinklered area showed some frost damage, but no more than the area covered by the overhead sprinklers.  And in California, where water is the most precious commodity, Carrillo can stomach small amounts of damage at such low temperatures if he can cut his water use in half.  Bottom line:  The 40 acres of Chardonnay he’s planning to plant will be protected with Pulsators.

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Surfing for Sprinklers

For more information on sprinklers – micro and otherwise – check out the Web site of the Center for Irrigation Technology at California State University-Fresno:  www.cati.csufresno.edu/cit. 

For details on the Pulsator, point your browser to www.waderain.com.