Role of Calcium in Pip Fruit Production

Calcium activates enzymes and is essential for cell division, elongation, and fruit growth. It stabilizes and ensures permeability of the cell wall, protecting it from degradation by enzymes. As a result, fruits with high levels of calcium are firmer and the skin and flesh is less liable to breakdown disorders with reduced leakage through cell wall membranes. Thus, good calcium supply delays ripening and increases storability of fruits.

Calcium effect at growth stages

Stage Calcium effect
Bud Burst – Start of Flowering Boost root and leaf growth and high yields
Fruit Set to Fruitlet at 30mm Maintain good fruit quality and minimise fruit disorders
Fruit Fill – Maturity Maintain good fruit firmness and storage quality
Post Harvest Maintain high levels in the tree
See more on Apple Growth Stages.

General Guidelines for Calcium Application

Calcium is taken up by root tips and transported to the leaves and developing fruitlets through the transpiration stream, via the xylem. At this stage, uptake is quite rapid and soil supplies are important.

By the time fruit reaches the fruitlet stage, over 50% of the final total amount of calcium will already be in the fruit. Thus it is critical that soil applied calcium has been applied before this stage.

However, at later stages, as the fruit rapidly expands, most Ca is transported to the leaves where it cannot be redistributed and so amounts in the fruit become diluted. At this stage, fruit sprays should be used to supplement calcium levels.

Calcium Deficiencies in Apples

Calcium is immobile in the phloem and can’t be remobilized from older tree tissues, so youngest leaves are the first to show symptoms, becoming chlorotic. New growth becomes stunted and fruit yield may be reduced.

Crop quality also deteriorates with reduced firmness and increased incidence of physiological disorders such as cork spot, sunscald and bitter pit.