Yellow leaf disease is a significant physiological issue in apple orchards located in alkaline soils. It occurs frequently and causes severe damage, leading to slow growth, reduced yields, weak shoots, or even tree death in severe cases. Research has shown that applying organic iron fertilizer during the dormant season, foliar spraying of compound iron fertilizer during early growth stages, or injecting a fruit tree rejuvenating agent into the trunk can effectively prevent and control this disease.
First, applying organic iron fertilizer around the tree. The preparation involves mixing ferrous sulfate with high-quality mature organic fertilizer in a ratio of 1:15. To prepare, dissolve the ferrous sulfate in 10 times its weight in water, then spray the solution onto the organic fertilizer. Mix thoroughly to ensure even distribution.
The application method involves digging a circular trench around the tree canopy, approximately 50 cm deep and 60 cm wide. After filling the trench with the organic iron fertilizer, water it after covering the soil. Trees over 10 years old typically receive 80–100 kg per tree, while younger trees (under 10 years) are given 30–50 kg per tree. This should be done in autumn or before bud break, avoiding the growing season to prevent potential plant damage.
Second, foliar spray of compound iron fertilizer. To prepare the solution, first dissolve 50 grams of citric acid in 50 liters of water. Then add 150 grams of ferrous sulfate and stir well. Once fully dissolved, add 100 grams of urea and mix again. Spray the solution in the early morning before 10 AM or late afternoon after 4 PM, ensuring even coverage with a fine mist.
Third, trunk injection of a fruit tree complex agent. This method is suitable for large apple trees over five years old. Drill three holes, each 7 mm in diameter and 5–6 cm deep, at 120-degree angles around the trunk. Remove any sawdust, then insert a sprayer nozzle into the hole. Fill the sprayer with a diluted solution of 0.05%–0.08% ferrous sulfate (20 times dilution), and inject the solution into the tree. A mature tree usually receives about 1 liter, while younger trees may need less. This technique helps restore tree health and reduce symptoms of yellow leaf disease effectively.
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