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Hay growers consider water needs; Researcher discusses effects of irrigation cutoff on alfalfa

Tam Moore for the Capital Press March 12, 2009

With costs up, prices down and California water supply problematic, hay producers face multiple hard decisions in 2009. YREKA, Calif. - The wheels came off federal marketing order milk prices this winter, and a lot of hay farmers are rethinking how they'll approach the 2009 production season.

Farmers and ranchers crowded into a conference room here Feb. 18 for the annual University of California growers seminar, which brought researchers to this farming and timber community just 40 miles south of the Oregon border. What they heard was a laundry list of issues that need decisions in the next few weeks.

There's already concern about prices for what is left of the 2008 crop, as some longtime dairy customers decline to pick up from growers' barns what they ordered. Eric Erba, from Visalia-based California Dairies Inc., told this winter's California Alfalfa Conference that low prices for milk and milk products can be expected through the third quarter of 2009.

But the biggest issue was water.

Irrigation water availability is an unknown, but it is likely to be in short supply despite recent storms. UC agricultural engineer Blaine Hanson, drawing on his research experience, said if growers anticipate surface or irrigation water shortages they should take the water up front and make the best hay with the first cutting.

Hanson headed a two-year study at forage sites from near Oregon to the scorching Imperial Valley at Holtville. In the intentional deficit irrigation tests, only the south-most site saw the perennial crop destroyed by a July water cutoff. Holtville recorded back-to-back days of more than 110 degrees in 2008. Deep-rooted alfalfa apparently responds to water stress by hunkering down, then rebounding the next year if the soil profile has enough moisture. Stand loss comes if soil moisture runs out.

The university undertook the complex study because California water managers hope for a way to price water sold to state or federal water banks, based on evapotranspiration rates of alfalfa fields, with and without irrigation water. About 1 million acres of alfalfa grow in the nation's top dairy state. The crop is rated the top consumer of irrigation water, on the order of 4 million to 5.5 million acre feet of water per year.

The theory is that in droughts, a mid-season transfer of water from a Northern California alfalfa field could become scarce water sent to dried-up locations to the south, or to augment fish flow in critical streams.

Hanson said it's time for California's Department of Water Resources to abandon the theory that farmers sell based on mathematical models created from alfalfa plant evaporation models. If there's to be a calculated state water bank value for alfalfa, he said, it should be based on predicted yields for crops raised with the full evapotranspiration rate satisfied, not a stand that gets half a season's water.

In Central Valley test sites with summer water cutoff, there sometimes wasn't enough growth to make it economical to harvest in late season. That means that even though there was some evapotranspiration, its only value was in keeping plants alive for the next year, not in making a salable hay crop.

Old data shows alfalfa stands in the desert need 76 inches of moisture a year, while those in the San Joaquin and Sacramento valleys needed 49 and 48 inches of moisture, and a field in the northern mountains demanded just 33 inches of water to make its crop.

That's not how it came out when the scientists tested real needs between 2007 and 2008.

"It is kind of hard to say what is going to happen," Hanson said of alfalfa yields in the deficit irrigation tests. "These results are all site specific. My conclusion is you 'just do what you want to do.'"

Freelance writer Tam Moore is based in Medford, Ore. E-mail: moore.tam@gmail.com.
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