Symptoms of Calcium Deficiency in Citrus and Methods for Its Prevention and Control
Release Date:
2019-02-15
Calcium deficiency symptoms: 1. Weak root growth and a reduced number of new roots. 2. Noticeable leaf drop in the upper canopy and widespread dieback; yellowing at the tips of spring shoots. 3. Increased susceptibility to sunscald, cracking, soft fruit skin, deformed fruits, and sour fruit flavor. Remedial measures: 1. Apply calcium fertilizer to the soil. For acidic soils, apply lime to adjust the soil pH to around 6.5—be sure to make gradual adjustments to avoid harming the root system. This lowers soil acidity and increases the exchangeable calcium content. Application rates depend on soil acidity: for citrus orchards just beginning to show calcium deficiency, apply 35–50 kg of lime per mu; for mature orchards with severe calcium deficiency, apply 1.0–2.5 kg of lime per tree. The method involves first spreading the lime between trees in the orchard or…
Characteristics of calcium deficiency
1. The root system is weak, with a low number of new roots.
2. Leaf fall and the presence of dead trees are conspicuous in the crown; the tips of spring shoots turn yellow.
3. Prone to sunburn, cracking, with soft skin, deformed fruit, and a sour taste.
Correction method
1. Apply calcium fertilizer to the soil. For acidic soils, apply lime to adjust the soil pH to around 6.5; be sure to make the adjustment gradually to avoid harming the root system. This will reduce soil acidity and increase the exchangeable calcium content.
The application rate depends on soil acidity. For citrus orchards newly showing calcium deficiency, apply 35–50 kg of lime per mu; for mature citrus orchards with severe calcium deficiency, apply 1.0–2.5 kg of lime per tree.
The method involves first spreading lime between trees or along the rows in the orchard, then plowing it into the soil within the area where citrus roots are densely distributed, mixing it thoroughly with the soil before irrigating. Calcium‑magnesium phosphate, superphosphate, and rock phosphate powder, among others, are rich in calcium and can effectively alleviate calcium deficiency symptoms in citrus.
2. Apply fertilizers appropriately. In acidic soils with low calcium content, in addition to liming, increase the application of organic fertilizers and reduce the use of acid‑forming chemical fertilizers such as nitrogen and potassium.
Do not apply lime in combination with organic fertilizers, as this may reduce their effectiveness. For sandy soils, consider replacing them with fertile, clayey soils or applying organic amendments to improve soil quality.
3. Foliar application of calcium fertilizer. During the new leaf expansion stage or the growing season, foliar spraying with a 0.3%–0.5% solution of calcium nitrate or a 0.5%–1.0% lime‑water extract can help correct mild calcium deficiency. Citrus trees have a high calcium requirement during flowering and fruit set; if obvious symptoms of calcium deficiency are already present, it is advisable to apply commercially available calcium fertilizers that employ chelation technology for rapid absorption and enhanced safety to ensure adequate nutrient supply.
4. Implement effective soil and water conservation measures to minimize the loss of calcium through soil and water erosion. In citrus orchards on sloping, acidic soils, it is advisable to construct level terraces with a higher outer edge and a lower inner edge; concurrently, adopt grass cover cropping on the terrace surfaces and apply mulch during the rainy season.
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