As part of the first really heavy precipitation California farmers have seen in more than a year, storms in the first week of February dropped 3-4 inches of rain on the farms and ranches of Tehama County. This ended the dry winter weather that had allowed walnut growers to finish up just about all their pruning work by the end of February. That’s also when another round of storms was predicted to bring more significant rainfall to the area.
While perking up spirits, the wet weather didn’t erase concerns about the ability of growers to meet the water needs of their trees this season.
“Drought is on everyone’s mind,” reports Richard Buchner, University of California Orchard Advisor for Tehama County. “Still, we can get rain in Tehama County into May and the snowpack in the mountains is also part of the water supply equation. So the game’s not over yet.”
Meanwhile, walnut growers are looking ahead to bud break. Typically, the late-leafing varieties grown in the county, mostly Chandler and Howard, start bud break around the first of April. That’s when the root zone of walnut trees should be filled with water, Buchner notes.
Many growers in the area began irrigating their orchards in the first week of November, following harvest. Keeping the roots hydrated helps the trees to continue producing carbohydrates, which are held in storage. Also, walnut trees in moist soil are less susceptible to frost damage, he explains. Depending on soil moisture evaluation, Buchner expects growers will irrigate again to top off their soil profiles before bloom.
Should this be another dry year with limited water supplies, growers will be deciding how best to allocate what water they have for this season. “Most strategies involve irrigating throughout the season, rather than putting all the water on at once in one big lump sum,” Buchner says. “You may not be able to provide as much water with each irrigation as normal, but you give the trees at least some water all the way through the season.”
The start of bloom also brings the threat of walnut blight and the need for fungicide applications to protect the trees. While wet, warm weather increases the disease risk, Buchner recommends taking action even if the weather is dry and cool at bloom. He suggests putting on a first spray at 40 percent prayer stage. That way, should rainfall occur, they have some protection from blight. A second application can be made about seven days after that to protect the later-opening buds. Decisions for additional applications are based upon the variety, weather and disease potential.
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