Phosphorus Deficiency in Citrus: Symptoms and Control Measures
Release Date:
2019-02-15
Phosphorus deficiency characteristics: 1. Spring shoots are few, thin, and sparse; leaves are small, narrow, dark green, with some tips turning brown and dying. 2. Significant impact on fruit: low yield, high incidence of misshapen fruits, and substantial pre-harvest fruit drop. Fruit skin is coarse, thick, and soft; juice content is low, acidity is high, and sugar levels are low. Fruits become soft, exhibit irregular shapes, and develop thicker, rougher skins. Correction methods: Phosphorus is easily fixed by the soil and is not suitable for broadcast application. Therefore, in phosphorus-deficient soils, from March to October, dig planting holes and apply concentrated deep‑burial fertilizers such as superphosphate, calcium‑magnesium phosphate, rock phosphate, and bone meal at a rate of 0.5–1.0 kg per tree. Since phosphorus has poor mobility in the soil and must come into direct contact with roots to be absorbed, when applying phosphate fertilizer, it should be placed directly around the citrus root zone.
Phosphorus deficiency characteristics
1. The spring shoots are few, slender, and sparse; the leaves are small and narrow, dark green, with some tips showing signs of dieback.
2. It has a significant negative impact on fruit quality, resulting in low yields, a high incidence of misshapen fruits, and substantial pre-harvest fruit drop. The peel is coarse, thick, and soft; the juice content is low, with high acidity and low sugar levels. The fruits become soft, exhibit irregular shapes, and develop a thicker, rougher skin.
Correction method
1. Phosphorus is readily fixed by the soil and is not suitable for broadcast application; therefore, on phosphorus-deficient soils, from March to October, dig planting holes and apply concentrated, deep‑buried phosphate fertilizers such as superphosphate, calcium‑magnesium phosphate, rock phosphate, and bone meal at a rate of 0.5–1.0 kg per plant.
Phosphorus has poor mobility in the soil and can only be absorbed by roots upon direct contact; therefore, when applying phosphate fertilizer, it should be placed in areas where citrus root systems are densely distributed, and it is best to mix it with organic fertilizer, compost it, and apply it deeply.
2. In acidic soils with a pH below 6.5, apply slow-release phosphate fertilizers that are less prone to leaching; in neutral or alkaline soils, apply quick‑acting fertilizers such as superphosphate or calcium‑magnesium phosphate.
3. In winter or during June–July, mature citrus orchards in red‑soil and red‑yellow‑soil areas should be applied with 1.5–2.5 kg of calcium‑magnesium‑phosphate fertilizer per tree, or with rock phosphate, bone meal, and similar amendments. For mature citrus trees growing in purple soils and other alkaline soils, apply 1.5–2.5 kg of superphosphate per tree; it is best to incorporate this fertilizer together with organic matter.
4. During periods of high temperature and drought, apply mulch to the soil surface to conserve soil moisture and enhance phosphorus uptake.
5. After new shoots have unfolded, spray the tree canopy with a 0.3%–0.6% solution of potassium dihydrogen phosphate or a 0.5%–1.0% extract of superphosphate. However, in regions with high temperatures and humidity, it is best to discontinue foliar applications of phosphate fertilizers after August to prevent excessive algal growth, which can impair leaf photosynthesis and reduce yield.
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