Saline soils temper Merced County tree nut crop

The almond crop in David Doll’s area appears a little lighter than last year’s bumper production.

“It looks like a more normal yield this year, except for growers on the West Side who are battling water shortages for the third year and row,” says the UC Cooperative Extension Merced County Farm Advisor.

Fortunately, he didn’t see too much “June drop.” That may be due to a heavier drop associated with the March frost, he says.

Walnuts look as good as last year and are progressing normally. In orchards he visited in mid-June, Doll was pleased by the uniform distribution of nuts throughout the canopy.

“That was probably due more to training style than anything, where wider spacing of the branches allowed more light to reach the inner canopy,” he says.

Without winter rains to flush out the soil profile, he’s been noticing a buildup of salts in sandier ground, especially in fields irrigated with salt-laden well water. Excessive salts reduce water absorption by tree roots. Salts can also move through the tree to leaf tips and margin; if enough accumulate, they can cause burn. “It’s most noticeable when evapotranspiration rates are high,” Doll says. “Salt burn is most dramatic in almonds mid-August to early September, when whole orchards can bronze over.”

Walnuts are much less susceptible to salt damage, he notes.

Doll recommends growers test their well water every five years for salt levels. If salt buildup is suspected, he says it’s a wise investment to sample the soil at depths of 1, 2, 3, 4 and 5 feet at several locations throughout the orchard.

“Usually, salt levels increase as you get deeper into the soil profile, because rains don’t move salts completely through the profile,” he says.

TAGS: Tree Nuts
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