Calcium plays a vital role in the growth and productivity of citrus trees. Despite its abundance in many soils, citrus trees can still experience calcium deficiency, which can negatively affect fruit quality, root development, and overall tree health. Here's everything you need to know about calcium’s role and how to prevent or address deficiencies.
The Role of Calcium in Citrus Trees
Calcium is the most abundant mineral element in citrus trees, making up about 1% of the tree’s dry weight. It is primarily found in the leaves, but fruit also contains calcium—approximately 4.4 lbs. per 100 boxes of oranges.
Calcium is essential for:
- Cell division and elongation: It’s a key part of cell walls and membranes, ensuring structural integrity.
- Root health: Calcium supports root development and reduces susceptibility to bacterial and fungal infections.
- Chromosome stability: It aids in cell division and activates important enzyme systems.
- Neutralizing acids: Calcium helps regulate organic acids in the plant.
An adequate calcium supply is critical to healthy plant growth and fruit yield, often before visible deficiency symptoms appear.
Calcium Deficiency in Citrus Trees
Citrus trees can suffer from calcium deficiencies even in soils with abundant calcium. This is because calcium availability depends on soil conditions, irrigation practices, and fertilizer use.
Symptoms of Calcium Deficiency
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Leaves:
- Fading chlorophyll along leaf margins and between veins (most visible in winter).
- Small necrotic (dead) spots in discolored areas.
- Thickened, small leaves with reduced vigor and thinning foliage.
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Fruit:
- Undersized and misshapen fruit with shriveled juice vesicles.
- Slightly lower juice content but higher soluble solids and acidity.
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Tree health:
- Twig dieback and poor new growth.
- Decreased fruit production.
Common Causes of Calcium Deficiency
- Acidic soils: Native calcium can leach from acidic soils, especially with continuous use of ammonium-based fertilizers like ammonium sulfate.
- Saline soils: Excess sodium (Na) in highly saline soils competes with calcium, reducing its availability.
- Potassium and sulfur fertilizers: Products like muriate of potash and sulfur-based fertilizers accelerate calcium depletion.
How to Prevent and Treat Calcium Deficiency
Long-Term Solutions
- Soil Testing: Regularly test soil pH and calcium levels to identify deficiencies early.
- Liming: Apply lime (calcium carbonate) to neutralize acidic soils and supply calcium. This is an economical and effective long-term solution.
- Gypsum Application: In saline soils, gypsum can supply calcium while reducing sodium’s negative effects.
Short-Term Solutions
- Foliar Sprays: Use water-soluble calcium sources, such as calcium nitrate, to address deficiencies quickly. Spray leaves for fast absorption.
- Manures and Compost: Organic matter improves calcium efficiency in crop production while enriching the soil.
Why Calcium Matters
Without sufficient calcium, citrus trees may struggle to develop properly, leading to reduced fruit yield and quality. By monitoring soil conditions and maintaining an adequate calcium supply, you can ensure your citrus trees remain healthy, productive, and resilient against disease.
[ One great resource: IFAS SS584 ]
