Water rationing until Sept. 1 is forcing some almond growers in California’s western San Joaquin Valley (SJV) to make tough water use choices this summer and fall which will likely result in reduced almond yields through next year.

Surface water supplies are limited due to two continuous years of below-average rainfall. Another reason is severe water restrictions caused a federal court ruling last year on the endangered Delta smelt that limited federal and state pumping from the Delta into the San Luis Reservoir. Water supplies are also low since this past spring was the driest on record.

The end result is reduced surface water supplies in some areas to finish this year’s tree crops.

“I’m lacking 30 percent of the water required to grow my almonds, peaches, and prunes during the rationing period,” according to Bill Diedrich, a farmer in Firebaugh, Calif. “I don’t have enough water for the month of August.”

Diedrich grows 500 acres of almonds, 75 acres of prunes, and 23 acres of peaches in western Fresno County. His main water source is federal surface water from the San Luis Water District (SLWD) where he’s also a board member. The district’s water is through the Central Valley Project (CVP), operated by the U.S. Bureau of Reclamation.

Due to the court decision on the smelt, Diedrich says inadequate off-line storage was secured for the peak irrigation season. This resulted in the rationing of water available to “south of the Delta CVP contractors.” Diedrich says the Bureau of Reclamation and the California Department of Water Resources (DWR) initiated rationing to prevent the CVP and DWR portion of the San Luis from falling below the minimum pool.

Diedrich is currently paying about $110 per acre-foot for district water. As for finding additional water during the rationing period, there is little to none on the market and the price is just about untouchable.

Diedrich’s allocated water this year is just 40 percent of what would be 2.4 acre-feet in a 100 percent delivery year. That’s less than one acre-foot per acre of the “normal” supply. Diedrich needs four acre-feet per acre to grow almonds. While some farmers are using well water to supplement their water needs, groundwater is not an option for Diedrich due to high boron and salt levels in the water.

“I’m in a very unsettled state,” Diedrich says. “I’m making daily phone calls to find additional water to finish the crops. I believe water will become available after Sept. 1, but that will be too late.”

The water shortage means 15 percent to 25 percent less water for the trees. Unless he locates more water soon, Diedrich expects a stick tight problem at almond harvest, the difficulty in removing nuts from trees.

“I won’t have any water for the important post-harvest irrigation period in almonds if I can’t secure additional water supplies in the next 30 days,” Diedrich says. “I have several leads, but nothing is secured yet.”

Diedrich primarily grows Nonpareil, Monterey, Butte, and Padre almond varieties. He applies water “efficiently and frugally” through double-line drip irrigation.

Yet Dietrich believes his almond crop is pretty much made. “It’s the prunes and peaches which are really in jeopardy because the trees can’t afford to be shorted water a month before harvest. Adequate water in August is critical for prunes.” His prunes and peaches are harvested in early September.

Almond growers who are short of water should reduce irrigations before harvest and save the water for post-harvest irrigation, according to David Goldhamer, irrigation management specialist with the University of California, Davis. He’s based at the Kearney Agricultural Center (KAC) in Parlier, Calif.

Goldhamer says almond trees require 6 to 8 inches of water over a six-week period immediately after harvest. Deficit pre-harvest irrigation is a better option in a water-shortage situation in the long term since post-harvest irrigation is essential to setting the next year’s almond crop.

“Deficit irrigating almond trees pre-harvest can result in fruit size reductions up to 20 percent,” Goldhamer says. “Insufficient post-harvest irrigation can reduce yields by 80 percent to 90 percent in the next crop year.” The latter is caused by inadequate bud morphogenesis (reproductive bud development).

“It’s a no brainer. Good post-harvest irrigation is a long-term investment toward profitability,” Goldhamer says.

Almond growers in the 1970s were unaware of the sensitivity of growth periods and related yield losses in almonds and other tree crops except apricots from inadequate water supplies.

Goldhamer’s work with Mario Viveros, recently retired farm advisor, in the 1980s (in Kern County) tested the timing of water stress in almonds and discovered post-harvest sensitivity. Even with full irrigation up to harvest, there was about a 40 percent reduction in yield the following year without post-harvest irrigation.

“My sense is there’s not a great panic out there now since growers know and understand the stress sensitive periods of almonds and other tree crops,” says Goldhamer. “The whole approach to water management in almonds has changed. I don’t think it’s coincidental that almond yields are much higher now. I believe good irrigation management is part of the reason.”

Almond varieties react similarly to water stress sensitivity; no variety (cultivar) fares better than another even though almond varieties are harvested at different times, Goldhamer says.

The water expert says reduced post-harvest irrigation minimally impacts pistachios, grapes, and tree fruit including peaches. Citing the work of Scott Johnson and Dale Handley at the KAC, peaches that receive 25 percent to 30 percent of the normal post-harvest water supply are minimally affected the next year, except for increased fruit doubling, Goldhamer says. Fruit doubles are thinned.

“If a farmer grows pistachios and almonds, they must decide where to apply limited water during September. Again, it’s a no-brainer; it goes on the almonds,” Goldhamer says. California pistachios are typically harvested in early to mid-September.

Walnut trees don’t tolerate stress periods well, yet insufficient research exists on how walnuts specifically handle post-harvest stress.

About a third of the almond acreage handled by the Central California Almond Growers Association (CCAGA), Kerman, Calif., is located in the western SJV. CCAGA is the largest almond sheller and huller in the world.

“I feel for those guys out there facing water reductions,” said Don McKinney, CCAGA chairman and an almond grower in Madera, Calif. “They’re in a world of hurt and their situation will not get any better in the near term.”

The water issue will likely reduce the number of almonds handled by CCAGA this year, McKinney says.

“Deficit irrigating results in a smaller nut size and lighter kernel,” McKinney says. “For growers who are lacking water and are deficit irrigating, the impact will be significant.”

McKinney has grown almonds for 39 years at his Dry Creek Ranch. He irrigates with well water for his 40 acres of Butte and Padre almonds. McKinney prefers to irrigate two to three times after harvest depending on the weather.

“Some of our West Side growers will really be short of water and that may not be possible. Even in the Madera area and the eastern side of the SJV, the limited supply of surface water can be a challenge if you don’t have good deep well water.”

McKinney irrigates with micro sprinklers. He prefers to flood irrigate the orchards once a summer to provide even water delivery across the orchard, and to disrupt ants that can build nests around the edges of the micro sprinkler pattern.

“I like to turn the water on as soon as the pickup machine gets out of the field to provide a three-day, 2 to 3-inch shot of water. Three weeks later I apply another 2 to 3 more inches,” McKinney says. “It all depends on the weather; will the temperatures stay hot causing the trees to use more moisture or will they cool off causing the trees to shut down.”

The USDA’s National Agricultural Statistics Service – California Field Office, released an objective almond forecast for the 2008-2009 crop year of 1.5 billion meat pounds based on 660,000 bearing acres.

Despite the impact of smaller yields from water shortages plus tree and branch losses to high winds this year, McKinney believes the estimate is on track. “I think the 1.5 billion pounds are there.”

email: cblake@farmpress.com