Symptoms of Magnesium Deficiency in Citrus and Methods of Prevention and Control
Release Date:
2019-02-15
Magnesium deficiency characteristics: 1. It can appear on leaves in any season, but progresses more rapidly in late summer and autumn. 2. Leaves bearing abundant fruit, especially those close to the fruit, exhibit more pronounced magnesium deficiency. 3. Typical symptoms occur on older leaves, with irregular yellow spots along the main veins; these spots gradually expand until only the leaf tip and base remain green, forming an inverted “V” shape at the leaf base. Remedial measures: 1. Apply soil amendments to improve soil conditions. For acidic soils such as red and yellow soils with a pH below 6, apply 0.5–1.0 kg per tree of calcium‑magnesium phosphate, magnesium oxide, or magnesium hydroxide. It is best to compost these materials with organic fertilizers like pig manure or chicken manure, then incorporate the resulting compost into the soil in spring. For alkaline soils such as purple soils…
Magnesium deficiency characteristics
1. It can manifest on the leaves in any season, but it progresses most rapidly in late summer and autumn.
2. The more leaves there are, the more pronounced magnesium deficiency becomes in those closest to the fruit.
3. Typical symptoms appear on older leaves, with irregular yellow spots along the main veins; these spots subsequently expand, leaving only the leaf tip and base green, while the green area at the leaf base forms an inverted “V” shape.
Correction method
1. Soil fertilization to improve soil quality. For acidic soils such as red and yellow soils with a pH below 6, apply 0.5–1.0 kg per tree of calcium‑magnesium phosphate, magnesium oxide, or magnesium hydroxide; it is best to compost these with organic manures like pig or chicken manure and incorporate the resulting compost into the soil in spring. Alkaline soils, such as purple soils, should not be treated with alkaline magnesium fertilizers like calcium‑magnesium phosphate or magnesium oxide; instead, use magnesium sulfate or magnesium nitrate. In soils where potassium and calcium concentrations are very high, magnesium exhibits a pronounced antagonistic effect and can inhibit root uptake of magnesium, necessitating an increased application rate. When applying fertilizer, dig a shallow circular trench 10–15 cm deep near the tree’s drip line and apply the fertilizer there.
2. Apply fertilizers appropriately. Increase the application of organic fertilizers and avoid excessive, imbalanced use of quick‑acting potassium fertilizers. For soils with high potassium levels, discontinue the use of potassium fertilizers and compound fertilizers, applying only nitrogen fertilizer to enhance magnesium uptake and utilization. In acidic soils, apply lime in moderation to reduce soil acidity.
3. Foliar fertilization. From April to May, after the new shoots have fully unfolded, apply a foliar spray of either a 0.2% magnesium nitrate + 0.2% zinc sulfate mixture or a 0.3% magnesium sulfate + 0.2% urea mixture; spraying magnesium sulfate alone yields poor results. Foliar application delivers faster results than soil application, but its efficacy is short-lived.
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