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Vineyard irrigation management advances to new level

Oct 18, 2007 10:15 AM, By Brenda Carol
Contributing Writer

It’s easy to coast through a “normal” season throwing a little water here and there at the vines as long as the reservoirs are full, the wells are running deep, and there are no environmentalists filing lawsuits to take water away from people for endangered species.

Throw just one monkey wrench into that scenario and suddenly it’s a whole different story. Try throwing three monkey wrenches into it like Mother Nature and the state legislature did this year, and that’s what California growers are dealing with today. Next season could get interesting to say the least.

“This season came on the heels of a fairly dry winter,” says Jim Smoot, viticulturist and independent vineyard consultant in Paso Robles, Calif. “We didn’t have the normal moisture in the soil profile at the beginning of the season, so we were starting out with a deficit.”

It was a good year to test the latest science regarding soil moisture, vine uptake and anything remotely related to water.

“We started using soil moisture monitoring this year,” says Jerry Grant, vineyard manager of Niner Wine Estates in Paso Robles. “The system that we are using now from Precision Ag Inc. takes hourly recordings and is much more accurate than the probes we were using before. The old method was very haphazard.”

The savings have been substantial, according to Grant. “We’ve cut our water use at least in half,” he says. “Then when you consider the fact that we’re not dealing with the ramifications of too much vigor in the vines, you can add to that the savings of not having to deal with excess canopy growth.”

The days of the neutron probe are passé, according to Lowell Zelinski, independent PCA and owner of Precision Ag Inc. in Templeton. “Today, more and more growers are turning to soil-based monitoring systems using capacitance sensors,” he says. “There are several soil moisture monitoring systems on the market, and in general, most provide similar information. However, they differ in how the information is delivered, what accessories are available, and of course, the cost. When the systems are installed and used properly, they are a valuable production tool.”

Zelinski believes that capacitance-based soil moisture monitoring is one of the best and most cost-effective ways to schedule irrigation in vines, trees and many other permanent and semi-permanent crops.

“Many methods of soil moisture monitoring are effective for telling you ‘how much’ to water but don’t tell you ‘when,’” Zelinski says. “To optimize plant health and the plant’s use of water and nutrients, knowing when to water is just as critical as knowing how much. With the capacitance sensors you receive accurate, reliable, visual data that can answer both questions.”

The soil moisture monitoring program at Niner Estates measures much more than just soil moisture. It’s almost a misnomer.

“We can track temperatures, rainfall, leaf moisture, soil water and a number of other factors,” Grant says. “This system is so precise that we can irrigate within 15 minutes of optimal time to irrigate. With the neutron probe, we were always working at least a week behind.”

With water at the forefront of every grower’s mind these days, conservation and optimal irrigation timing is perhaps a concept worthy of investigating. “I give people an honest assessment of the various methods of monitoring their crop’s water and nutrient requirements and how they affect irrigation scheduling decisions,” Zelinski says. “Each system has its advantages but I have found that the capacitance-based soil moisture monitoring really provides the most accurate, reliable data.”

He is particularly partial to the EcH20 system from Decagon. “It’s less expensive than most systems and the probes are easier to install,” he says. “They are continually developing new instrumentation to enhance the system to give growers other ways to monitor their crops such as the leaf perometer — a handheld device that measures stomatal conductance. An ET monitoring station should be released in 2008. The EcH20 line also includes sensors that measure air temperature, relative humidity, rainfall and irrigation events, and leaf wetness.”

Regardless of the system, Zelinski believes that irrigation conservation is critical to the long-term viability of the wine grape industry. The bonus for growers is that it’s not all that difficult to implement.

“Soil moisture monitoring isn’t exactly rocket science,” Zelinski says. “However, it is new technology and there is a learning curve. A user’s knowledge level can impact their experience with the equipment, the equipment’s effectiveness and the value they receive from it.”

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