Applying magnesium to citrus trees can be done effectively through two primary methods: directly to the soil around the root zone or dissolved in water for soil application, always followed by thorough watering.
Why Citrus Trees Need Magnesium
Magnesium is a vital macronutrient for citrus trees, playing a crucial role in photosynthesis as it is a central component of chlorophyll. A deficiency can significantly impair the tree's health and productivity. Common symptoms of magnesium deficiency include interveinal chlorosis, where the areas between the leaf veins turn yellow while the veins themselves remain green, often starting on older leaves. For more details on identifying citrus nutrient deficiencies, reputable agricultural extension services like the University of California Agriculture and Natural Resources offer comprehensive guides.
Common Magnesium Supplements for Citrus
Several forms of magnesium can be used for citrus trees:
- Epsom Salts (Magnesium Sulfate): This is the most common and readily available option for home gardeners. It's water-soluble and provides magnesium relatively quickly.
- Magnesium Oxide: A slower-release form of magnesium, often used in commercial applications.
- Chelated Magnesium: These forms are bound to organic molecules, making the magnesium more available for plant uptake, especially in challenging soil conditions.
Methods for Applying Magnesium to Citrus
Proper application ensures the magnesium reaches the tree effectively without causing harm.
1. Soil Application (Root Zone)
This method delivers magnesium directly to the roots, where it can be absorbed.
- Direct Granular Application:
- Measure 20 grams (approximately 1 ¼ tablespoons) of your chosen magnesium supplement for every metre of the tree's height.
- Evenly sprinkle the measured amount around the base of the tree, extending to the drip line (the outer edge of the canopy).
- Dissolved Liquid Application:
- Dissolve 20 grams of magnesium supplement in 1 litre of water.
- Apply this solution to the soil around the root zone of the tree. Scale the amount based on tree height; for instance, a 2-metre tall tree would require 40 grams dissolved in 2 litres of water.
- Crucial Step: After applying magnesium to the soil, water in well. This is essential to help the magnesium dissolve and move down into the root zone for absorption. It also washes any product off the plant foliage, preventing potential leaf burn.
2. Foliar Spray Application
Foliar application provides a quicker, though often temporary, boost of magnesium by allowing the leaves to absorb the nutrient directly. This method is often used for a rapid response to visible deficiency symptoms.
- Preparation: Dissolve 1-2 tablespoons of Epsom salts per gallon of water. Use warm water to help the salts dissolve completely.
- Application: Spray the solution evenly over all the leaves, ensuring both the top and underside surfaces are thoroughly covered.
- Timing: Apply foliar sprays during the cooler parts of the day (early morning or late evening) to prevent rapid evaporation and potential leaf burn.
Dosage Guidelines and Frequency
Accurate dosing is important to provide sufficient nutrients without over-application, which can lead to imbalances.
| Tree Height (Metres) | Magnesium Dosage (grams) | Magnesium Dosage (Tablespoons approx.) | Water for Dissolving (Litres) |
|---|---|---|---|
| 1 | 20 | 1 ¼ | 1 |
| 2 | 40 | 2 ½ | 2 |
| 3 | 60 | 3 ¾ | 3 |
- Frequency: For established trees, magnesium can typically be applied once or twice a year, especially in spring and early summer, or when deficiency symptoms become apparent.
- Soil Testing: To determine the precise needs of your trees, consider performing a soil test. This can identify specific nutrient deficiencies or excesses and guide your fertilization strategy.
Important Considerations for Effective Application
- Watering In: This cannot be stressed enough for soil applications. Thorough watering ensures the magnesium reaches the roots and prevents any concentrated product from damaging surface roots or foliage.
- Soil pH: The availability of magnesium can be influenced by soil pH. Citrus trees thrive in slightly acidic soil (pH 6.0-7.0). If your soil pH is too high or low, magnesium may not be as readily available even if present.
- Avoid Over-application: While essential, excessive magnesium can interfere with the uptake of other nutrients like calcium and potassium, leading to new problems.
- Monitor Your Tree: Observe your citrus tree closely after application. Look for signs of improvement in leaf color and overall vigor over several weeks.
General Citrus Care Tips for Optimal Health
Beyond magnesium, a holistic approach to citrus care ensures robust growth and abundant fruit production:
- Consistent Watering: Provide deep, regular watering, especially during dry periods and fruit development.
- Balanced Fertilization: Use a fertilizer specifically formulated for citrus, providing a balanced blend of nitrogen, phosphorus, and potassium, along with other micronutrients.
- Adequate Sunlight: Citrus trees require at least 6-8 hours of direct sunlight daily.
- Pest and Disease Management: Regularly inspect your trees for signs of pests or diseases and address them promptly.
