Orchards, pastures feel effects of dry February

Issue Date: February 26, 2020
By Kevin Hecteman

Warm, sunny days are a California trademark. But when it's February and the rain gauge is nearly empty, all that "nice" weather can be worrisome.

Brian Fedora, who grows walnuts in Colusa County, said his trees should start pushing in about a month; with temperatures peaking in the 60s and 70s, he's wondering about the cold.

"It is concerning, because we do rely on those chill units," Fedora said.

Katherine Jarvis-Shean, a University of California Cooperative Extension orchard advisor in Sacramento, Yolo and Solano counties, said the amount of chill appears adequate.

"(It) seems like it's been cool enough so far despite a warm spell in the middle of December and a warm spell at the end of January," she said.

As of last week, the Central Valley as a whole had recorded 914 chill hours and 59 chill portions.

Jarvis-Shean said that put the region "comfortably above" the chill accumulation for the winter of 2014-15, when lack of chilling led to "problematic" tree behavior.

There's been a shift in how cold weather is measured. Chill hours, Jarvis-Shean said, are a metric invented in the 1940s and measure hours during which the temperature is below 45 degrees, or between freezing and 45 degrees.

The newer metric, chill portions, is more nuanced and gives credit for temperatures into the low 50s, she said.

"That's a more realistic range in the Central Valley," she said, "where we have more mild winters that are cool but not necessarily cold."

Another crucial difference: A warm day can cancel out chill time an orchard might have accumulated the night before. Jarvis-Shean defines warm as being in the high 60s or 70s, adding that the chill-portion metric "ends up rewarding consistent cold."

Without that, "you have problems getting flower buds to push at all, or leaf buds, too, for that matter," she said. "That's pretty darn rare to get that low, and that's certainly not the ballpark we're in this year."

In walnuts, insufficient chill can lead to a long bloom window, Jarvis-Shean said.

"The problem then is that you have some nuts that essentially start the race earlier than the other ones," she said. "You have a longer bloom window that can result in a longer harvest."

Sizes will vary widely, she noted, and farmers aren't likely to earn much from the smaller walnuts.

Fedora noted other factors may also be at play when walnut trees fall short of potential.

"We can all make assumptions, but the trees aren't going to tell you, other than not producing," Fedora said. "You can't pinpoint them down and say, well, was it the chill units or was it the heat in the summer? Was the summer not hot enough for us? Do we not have enough submoisture?"

Forage for cattle could also be an issue this winter.

Theresa Becchetti, a UCCE livestock and natural resources advisor in Stanislaus and San Joaquin counties, said forage usually starts germinating with fall rains sometime in October; in a typical year, there's enough soil moisture from December-February rains to dramatically boost forage production. The period in between she calls "adequate quality and inadequate quantity"—the protein level is high but there's not enough of it to go around.

"This year, we started with good germination and good fall rains, similar to some of our past drought years," she said. "Forages stopped growing as temperatures dropped in December and January. If we start to get storms to come in soon, we can still have another 'miracle March,' but the warm temperatures this February have caused some of our annual forages to already move from growth stage to reproduction stage."

If that happens to too many of the forages, she said, a "miracle March" won't help, as the plant will produce a seed and call it a year.

"If our weather moves back to a more normal pattern for this time of the year, cooler temperatures and rains, we can end the forage season with normal production," Becchetti said. "Ranchers would have experienced a longer inadequate-quantity period, meaning they either had to find more rangelands to graze, or fed more hay or another supplemental feed."

The next few weeks should give a better idea as to how the season will play out, she added.

Back in the orchard, Fedora said he prefers to remain optimistic. He's not irrigating at present but plans to reassess at the beginning of March.

"Luckily, the dams have got pretty good water in them at this point in time," Fedora said, "but we're missing a snowpack."

Idamis Del Valle, a meteorologist at the National Weather Service office in Sacramento, said a persistent high-pressure ridge has been pushing storms to the north and leaving California dry. Del Valle said the rest of February was likely to be more of the same in Northern California.

Almost 60% of the state is abnormally dry, and 10%—roughly the Central Valley and foothills from Tuolumne to Kern counties—has slid into moderate-drought status, according to the U.S. Drought Monitor.

"I think we'll be OK for this year," Fedora said, "but then you have to start thinking for the years down the road and what will happen if next year isn't a wet year. We can always survive one year, but it's the multiple years that become a huge problem."

(Kevin Hecteman is an assistant editor of Ag Alert. He may be contacted at khecteman@cfbf.com.)

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.




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