Ways Apple Growers Can Master Micronutrient Mechanics

Healthy looking apple cluster

Calcium and boron are critical nutrients in apple development, quality, and yield.
Photo courtesy of BRANDT

One of the most frequently mentioned elements in the apple grower’s micronutrient arsenal isn’t even a micronutrient.

“I keep saying calcium is a micronutrient. It’s not. It’s a macronutrient,” Andrew Pedersen, Product Development/Technical Services, BRANDT, says. “But it often times gets treated as a micronutrient and bundled into that same market space.”

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With good reason, according to Pedersen and his industry colleagues.

Fix on Foliar

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Several of the new higher-value varieties of apples, particularly ‘Honeycrisp’ in Washington state, are more susceptible to calcium disorders such as bitter pit, Pedersen says. That “greatly increases” the potential need for foliar calcium sprays and other micronutrients that may go along with it, he says.

Foliar application is definitely the way to go, Ken Dart, National Technical and Marketing Manager, Agro-K, says. “Coming out of the soil, the calcium goes to the leaves and not to the fruit,” Dart says. “We don’t grow and store and sell leaves; we grow and store and sell fruit. And the only time to get it into the cell wall of the fruit, to do what you want it to do, is to apply it foliarly during the cell-division phase of that fruit growth.”

As bitter pit and other calcium disorders continue to hinder growers, nutrient synergy is vital, according to Dan Skoczylas, Director of Sales and Marketing, Nutrient Technologies.

“Focusing growers and consultants on micronutrients that influence fruit quality and fruit finish helps growers maximize return on investment, especially in harder-to-grow varieties like ‘Honeycrisp,’,” Skoczylas says. “While there is a tendency to think about micronutrients on an individual basis, such as calcium, zinc, or boron, there needs to be a significant synergy between them to optimize plant function.”

Alex Duffy of Timac Agro inspects apples

Timac Agro USA wants to see growers include tissue, soil, and sap testing to better understand how nutrients move from their specific soils to the trees and then respond only when there is reason. “I see a lot of potassium and magnesium going out to aid in fruit color,” National Product Manager Alexander Duffy says. “There is not much research supporting these applications, and if the tree does not need these nutrients, it can actually increase the incidence of bitter pit and hurt final yield.”
Photo courtesy of Timac Agro

Additional Micronutrient Tips

  • When evaluating the success of foliar micronutrient applications, Pedersen says growers should ask laboratories to wash all tested leaf samples, preferably by acid wash. “A lot of micros, like zinc and iron, won’t come off the leaf surface unless you conduct an acid wash,” Pedersen says. “If you want to really tell how much of the micronutrient got into the leaf and into the plant, the lab has to do an acid wash prior to analyzing the composition. That’s something that a lot of people assume is done in the lab, but it’s good to check with whatever labs the growers are sending their samples to and ensure that is something that is being done.”
  • Dart recommends that growers take the 4 R’s of nutrient stewardship – right source (nutrient), right time (crop stage), right rate (mix), and right place (in tree), in that order – and sandwich a fifth principle, right formulation, in the middle of the strategy. “It’s very important to get the form right as well. Otherwise, growers are just spraying expensive paint,” Dart says. “I’m a believer in the 5 R’s,” and among those best practices “timing and form become really important. … Am I getting to the right place in the tree? To do that goes back to the question of right form. Only certain forms will go from the vascular system down to the roots.”
  • Growers should be consistent in their testing, Ferticell Marketing Director Matt Brill says, so they can predict deficiencies before they become an issue. “A well-thought-out program with a solid base of data and a plan to curb any abiotic or biotic stresses that could slow fruit production should be ready should an issue arise in test results,” he says.
  • KeyPlex President Gerald O’Connor says quality fruit requires quality micronutrient inputs. “Most growers know this, but it gets lost as margins are squeezed. Using cheap inputs delivers unnecessary toxins to the plant and soil, thus affecting quality of fruit overall. It’s a vicious circle,” he says.
  • Interested growers should request information from manufacturers, distributors, and local experts, Randy Edwards, Vice President of U.S. Sales, Miller Chemical and Fertilizer, says. “Find a consistent, trusted source of information,” he says. “Miller employs numerous agronomists across the country, as do many other suppliers. They are a wealth of information and are available at a simple mouse click.”

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