Yellowing leaves can have complex causes-not only nutrient deficiencies but also insufficient light, water stress, and other factors. Below are 10 common causes and their corresponding remedies.
1. Nitrogen Deficiency
Older leaves turn yellow first, with yellowing progressing from the bottom of the plant upward. Apply nitrogen fertilizer such as urea, ammonium bicarbonate, or ammonium sulfate-either through the roots or as a foliar spray-or use a high-nitrogen water-soluble fertilizer to help restore green leaves.
2. Phosphorus Deficiency
The entire plant turns dark green and loses its gloss, and leaves may also yellow. Apply phosphorus fertilizer such as superphosphate to help leaves regain their shine.
3. Potassium Deficiency
Leaves become uneven or puckered, and leaf margins may turn yellow and dry. Apply potassium fertilizer such as wood ash, potassium sulfate, or powdered mono potassium phosphate (MKP) to relieve the symptoms.
4. Iron Deficiency
Both young and old leaves yellow at the same time. In young leaves, the tissue between the veins turns yellow while the veins remain green, forming a network-like pattern. Ferrous sulfate is commonly applied, but the concentration should not be too high-apply it in stages to avoid root burn.
5. Calcium Deficiency
Young leaves turn yellow and curl. Applying crushed eggshells or an imported chelated calcium-magnesium fertilizer can reduce the damage.
6. Magnesium Deficiency
Leaves lose their green color and turn yellow, then dry up and die. Apply calcium-magnesium phosphate fertilizer or magnesium sulfate.
7. Sulfur Deficiency
Leaf veins turn yellow. Apply ammonium sulfate and similar fertilizers to help the leaves turn green again.
8. Strongly Alkaline Soil
Yellowing can also occur in strongly alkaline soil. Apply acidic materials such as rice-washing water or ferrous sulfate to adjust the soil environment.
9. Improper Watering
Overwatering or waterlogging causes young leaves to yellow, while excessive drought causes older leaves to yellow, with yellowing worsening from the bottom upward and possibly leading to the death of the whole plant. Regulating soil moisture can effectively remedy the problem.
10. Over-Fertilization
Applying too much fertilizer, or fertilizing at intervals that are too short, causes fertilizer burn. Young leaves become uneven or puckered but remain thick and glossy. Control fertilization, water appropriately, and loosen the soil by hoeing to relieve the symptoms.
In addition, some plants develop yellow leaves under natural conditions such as strong light exposure, insufficient light, or high temperature and humidity. Judge the cause based on the actual situation and take corresponding preventive measures.
