California’s $2.1 billion, 740,000-acre almond industry depends heavily on added nutrients to produce high quality nuts, maintain tree health and provide financial viability to growers.
“The goal of almond growers is to get trees in production as soon as possible and maintain high production to cover cost margins,” said almond farm advisor Paul Verdegaal, University of California Cooperative Extension, San Joaquin County, Stockton, Calif.
Almonds, along with other nut and fruit trees, require large amounts of nitrogen and potassium. Some of the nutrients are returned to the soil through mulching, composting, and other “natural recycling.”
More potassium is required than nitrogen in almond production since higher levels of potassium move into the fruit. Potassium improves the bloom and crop set while aiding in plant water movement in the leaf’s essential photosynthesis process.
California’s worsening three-year drought is generating more phone calls to Verdegaal’s office. While growers have boosted irrigation, they still express concern over unhealthy-looking trees. In some cases, the net cause is the lack of essential nutrients, made worse by water stress.
“Improper nutrient status in the tree can make other stresses including drought and pests more evident,” Verdegaal said.
Potassium deficiency in almond trees takes several years before the symptoms appear. Adequate fertilization maintains healthier trees more capable of combating pests and diseases.
For many nutrients, excluding nitrogen, Verdegaal says leaf tissue sampling in the late spring-early summer and prior to harvest provides the most accurate nutrient readings.
A popular source of potassium for almonds, sulfate of potash (SOP) or potassium sulfate, includes potassium and sulfur.
“Sulfate of potash is slightly more expensive to produce and purchase but growers get a good amount of sulfur for the amount of sulfate of potash applied,” Verdegaal said.
Sulfate of potash is a fairly safe form of potassium without too much chloride, Verdegaal says. In dry or poorly drained locations, the use of another potassium source, potassium chloride, can result in too much chloride which is unhealthy for the tree.
Potassium is generally applied to the soil through micro sprinklers and drip irrigation.
“Potassium can be helpful through a foliar application in severe situations where a grower needs a quick response to the leaves and canopy to quickly correct a problem,” Verdegaal said. “Foliar sprays are a last-minute, temporary, and expensive way to deliver potassium to trees.”
Andy Dugo, a pest control adviser for more than 30 years, agrees that growing a high- quality almond crop requires a proper nutrient program.
“Many people say nitrogen is the number one nutrient requirement of almonds,” said Dugo of Mid-Valley Agricultural Services, Escalon, Calif. “If you look at the numbers, there is more potash removal in a one-ton crop.”
“Sulfate of potash is a tremendous, needed nutrient in almonds – much more so than nitrogen,” Dugo said. “An amazing thing happens when you put potassium in an orchard – production goes up. That’s pretty much true across the board.”
Dugo says adequate potassium levels are at the 2.0 level or higher in tissue samples.
“If my customers can afford it they try to get to the 2.4 to 2.5 level,” Dugo said. “500 to 800 pounds of sulfate of potash is a nice application.”
While some well water can supply 20 to 40 units of nitrogen a year to a tree, well water contains no potassium. This is one reason why almond trees require more added potassium than nitrogen.