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Saving water, getting good yields with irrigation technology

By TAM MOORE Oregon Staff Writer


Automated and, in some cases, radio or cell-phone connected soil moisture systems are under evaluation at UC Intermountain Research and Extension Center. The devices are grouped in a commercial potato field.

TULELAKE, Calif. — Water’s always been precious to farmers of the Klamath Basin.

Two events, one recent history, the other a near-certain future, turn up the pressure to make every drop count. Information gathered here may help farmers across the irrigated West. It has practical use for basin farmers eligible for special Klamath water-conservation cost-share programs contained in the 2002 farm bill.

Dozens of experiments and tests of applied irrigation technology fill plots at the University of California Intermountain Research and Extension Center located at Tulelake, just one mile south of the Oregon border. Superintendent Harry Carlson turned the station’s late July field day into a mid-summer seminar on practical irrigation.

The station is within the federal Klamath Reclamation Project where the 2001 drought and the federal Endangered Species Act combined in a nationally publicized U.S. Bureau of Reclamation repudiation of irrigation delivery contracts. Uncertainty over water delivery continues within the project.

Electricity to run agricultural pumps within the Klamath Project comes with a discounted rate — part of the 50-year federal energy license to PacifiCorp. The power company says it has no intention of repeating those rates as part of the next hydroelectric system license due in 2006.

Figuring out how to control future electricity cost is on the mind of most farmers these days, and topic one for a special committee of the Klamath Water Users Association.

Carlson began practical irrigation experiments over a decade ago, aimed at better yields on potatoes and onions, two of the basin’s highest value crops.

Said Carlson, the bottom line is that the best irrigation schedule is a combination of estimates for crop water use, actual measurement of soil moisture and adjustments for actual and anticipated local weather conditions.

“There is no silver bullet for irrigating in the wind with solid-set sprinklers” when velocity goes over 10 miles an hour, he added.

Research continues in 2004, including evaluation of six potato varieties under different irrigation routines, using solid-set sprinklers spaced at 15-foot intervals. That’s half the spacing used in most commercial farms, and a chance to not only see growth response to water but monitor incidence of disease related to humidity beneath the leafy canopy of vigorous spud varieties.

There’s what may be the basin’s first trial of buried T-tape drip irrigation beneath onions. Kevin Stewart of T-Tape System estimates that elsewhere 10,000 acres of onions, primarily in Idaho, are dripped this season. Four Idaho potato growers have indicated interest in trying commercial-sized drip systems.

Stewart is working with the Tulelake station’s Don Kirby, who heads up the farming crew. Kirby said problems came in getting uniform seed germination in a dry spring.

“I didn’t see water and I panicked, and really poured on the water,” he said. “But the onions did start emerging, and there was too much water; they turned yellow (on the tops).”

Two of Carlson’s ongoing projects are evaluation of sprinkler uniformity — how water is distributed in windy conditions — and making site-specific crop water models.

There are jokes about the “field of cans,” an array of 400 No. 10 cans around a single sprinkler head. Data collected there, and matched with wind speed and direction recorded by an adjoining weather station, is used to plot actual water delivery.

“After 10 years I’ve finally got it right,” Carlson said of the testing, overseen this year by Jessica Horsley, a research assistant.

Water measured in low-tech tin cans, fed to sophisticated computer programs, turns into predictions of irrigation efficiency, at various wind speeds and directions, for specific types of sprinkler heads and nozzle sizes. Evaluations of seven sprinkler types with 58 variations for nozzle size or operating pressure and wind speed are available. So are computerized graphs predicting actual coverage of various solid-set configurations.

In a field of spuds growing under commercial conditions, there’s an array of off-the-shelf soil moisture sensors linked to electronic reader systems. By mid-summer, evaluating three different sensor manufacturer’s measuring scales, Carlson said there’s consistent data that relates to soil moisture collected by the neutron probe, a standard device used by crop researchers. Any one of the systems will do the job, he said; it’s just a matter of getting familiar with the electronic data offered by the particular manufacturer.

Tam Moore is based in Medford, Ore. His email address is cappress@charter.net.


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