Role of Calcium in Citrus Production

Calcium is a key component of cell walls and also has a direct influence on the regulation of enzyme systems, phytohormone activities and nutrient uptake. Calcium also influences pollen tube elongation and seed formation.

Calcium effect at growth stages

Stage Calcium effect
Flowering To aid leaf growth, pollination and fruit set
Fruit Set Provide good fruit productivity and quality
Fruit Enlargement and Maturation Boost leaf growth and tree vigour and reduce skin disorders including fruit splitting and albedo breakdown
Post Harvest To maintain tree root health and productivity and to encourage leaf flush
See more on Citrus Growth Stages.

General guidelines for Calcium application

Annual, cumulative use of calcium produces high yield. Calcium nitrate ensures higher yields compared to ammonium nitrate. Fertigation using calcium nitrate is a highly effective way of maximizing Ca nutrition and yield. Significant fruit set improvements come from calcium nitrate applications made immediately prior to and during flowering.

Calcium deficiencies in citrus

There are few visual signs of calcium deficiency in the leaf. Leaves may show interveinal symptoms similar to iron or manganese deficiencies but these are rare. Leaves with calcium levels below 1.6% are deficient, however, trees lack vigor and start defoliating when the leaf calcium level falls below 3%.

Calcium deficient trees are stunted due to poor root development, with dark green foliage. The main impacts of calcium deficiency are root systems that are more susceptible to root diseases and fruit which is more prone to albedo breakdown and splitting.