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Bitter Pit and Honeycrisp: How Much Calcium Are You Getting?

Reducing bitter pit in Honey Crisp and other sensitive apple cultivars continues to be a challenge. Effective bitter pit management requires integrating cultural, soil, water, and crop nutrition practices. Applying calcium (Ca) sprays every two weeks during the growing season, often beginning in mid-June, for a total of 4-8 applications is one management tool.

There are many calcium products available, but the product used is not as important as the total amount of actual calcium applied over the season. To maximize the potential benefits up to a total of 12 kg actual calcium/ha per season is often required. This is usually applied in four or more sprays.

Regardless of which calcium product you may choose, it is important to know how much actual calcium the product selected provides over the season.

Example 1: Dry calcium product

Calcium chloride (78% technical grade) contains 27.8% calcium, and is applied at of 5 kg/ha per application. Maximum 8 applications (from label).

Total calcium applied per season = (% calcium in product ÷ 100) X product application rate/ha X number of applications

(27.8 ÷ 100) X 5 kg/ha X 8 = 11.1 kg

Example 2: Liquid calcium product

Product with 6% calcium, applied at 6 L/ha per application. You also need to know the product's container weight (24 kg) and its volume (20L). Maximum 8 applications (from label).

Total calcium applied per season = (% calcium in product ÷ 100) X (Product container weight ÷ product container volume) X product application rate/ha X number of applications per season

(6 ÷ 100) X (24kg ÷ 20 L) X 6 L/ha X 8 = 3.5 kg

These simple calculations allow you to compare how close to the desired 12 kg actual calcium per ha per season each product applies. Deciding on which calcium product best suits your bitter pit management program also depends on how effectively it integrates with your other strategies. But it is important to know how much actual calcium you are applying over the season."

More information on managing bitter pit can be found in OMAFRA Factsheet, Bitter Control in Apples , Order No. 00-009 or online at:
www.omafra.gov.on.ca/english/crops/facts/00-009.htm