Calcium: Three Golden Rules for the Almond Grower

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(Sponsored) After bumper yields lifted almond growers’ hearts and spirits in 2020, it’s still too early to say how 2021 will turn out. First indications will come with February’s bloom, but it’s still not too late for some nutrition planning to maintain yield potential should 2021 deliver another season of almond-friendly conditions, says agronomist Francisco Rivera, of California-based OMEX® Agrifluids.

“Why are almonds known as a ‘superfood’?” Francisco asks. “Because they’re packed with potassium, calcium and protein ‘built’ from nitrogen.

“Average nut set reported by USDA in California was 5,645 kernels, a 20 per cent increase on 2019,” he points out. “All those extra kernels demand a lot of nutrients from the tree. It’s easy to see how, after such a heavy crop, nutrient levels in the tree can fall dangerously low.”

Francisco says it’s essential that growers take steps to raise these nutrient levels before the tree needs them again. “Nitrogen for vegetative growth, bud formation and nut protein; potassium for growth, water optimization and nut-fill; and calcium for high quality, disease-free nuts.”

But of the three nutrients in question, calcium is one to watch. “Very early in the season, even after a heavy harvest the previous year, trees will continue to take nitrogen and potassium from reserves, at least until top-up treatments can be applied ahead of key events such as fruit set and during development.

Rule #1

“Calcium, however, is a different matter — and it’s the first golden rule to remember: crops cannot store excess calcium.”

Unlike potassium and many other nutrients, Francisco explains, plants have no capacity to store reserves of calcium. In fact, once they’ve topped-up their calcium storage — in the calmodulin proteins between the cell wall and cell membrane — any excess calcium is ejected through the leaves, even if fruit or nuts are displaying calcium deficiencies.

“This also sheds light on why tissue testing for calcium is so unreliable,” warns Francisco. “Not only is there no connection between leaf tissue calcium and fruit tissue calcium, but the difference between acceptable levels and deficiency can be as small as 2ppm — outside any analytical tolerances.”

Rule #2

The second golden rule is that calcium can only move up. “Plants can’t move it from one place to another,” says Francisco, “because it’s not phloem mobile. Instead it moves through the xylem, following water through the tree from the roots to the places of highest water loss — usually the top-most leaves.

“This explains why any water-related conditions — drought, waterlogging, wind — can bring about calcium-related quality problems.”

Rule #3

Finally, calcium transport into cells is directly influenced by the plant hormone auxin. If there’s no auxin present, then crops won’t absorb calcium properly, irrespective of how much is applied.

“Auxin is involved in cell division,” explains Francisco. “New tissue — as found in developing nuts — has high auxin levels and can absorb good levels of calcium. But once the nut has all its cells and shifts to cell expansion — the maturing nuts — its ability to absorb calcium decreases rapidly.

“Young nuts absorb calcium well; maturing nuts will struggle.”

Understanding this aspect of the tree’s physiology was crucial in helping a British agri-tech company, Levity Crop Science, create the science needed to support better calcium nutrition. Its research team came up with two technologies, LimiN and LoCal, to circumvent the problem. Both are available in the U.S. through a unique partnership between OMEX® and Levity.

“This technology is like nothing else in the market,” enthuses Francisco. “When we evaluated the Levity tech as an additive to our own products, we couldn’t wait to incorporate them and bring their benefits to our customers here.

“We incorporated the LimiN technology within Cell Power® SizeN®, co-formulated with calcium,” he continues. “LimiN comprises a stabilized amine nitrogen, which emphasizes root growth and a good compact habit, characteristics required for a nut tree’s ability to supply calcium to the nuts.”

When trees receive standard nitrogen, reduced root growth and focus on apical shoot growth can create a huge calcium sink at the top of the tree, diverting calcium from blooms and nuts.

The second technology, LoCal, uses a naturally occurring compound to mimic the effect of auxin, allowing plants to properly absorb calcium where they would normally have a low ability to do so. “Cell Power® Calcium Gold and Cell Power® Calcium Platinum both use LoCal technology to supply nuts with calcium very effectively, ensuring good nut fill and improving tolerance to disease and molds,” says Francisco.

He recommends almond growers start with Cell Power® SizeN® Ca, applied as a dormant spray — 1% solution to soak bark — one to four weeks before bud-break. “Four follow up applications of Cell Power® SizeN® K, through drip, will help keep roots alive, maintain a good shape and create the conditions for high nut yield.”

Meanwhile, applications of Cell Power® Calcium Gold and Cell Power® Calcium Platinum are best started at flowering. “Apply at 1 pint/acre, then top up after two weeks with a final one ahead of harvest. This will reduce shell seal breakdown and increase yield.”

Learn more at

The product names and brands referenced here are registered and trademarks of OMEX® Agrifluids, Inc.

© OMEX® Agrifluids, Inc. 2021.


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