Leaf yellowing (chlorosis) occurs when chlorophyll in the leaves decreases, directly reducing photosynthesis. But yellowing has more than one cause; the right solution requires correctly diagnosing it first. This guide explains how to distinguish the cause by looking at where yellowing begins, and how to fix it.
The Key to Diagnosis: Where Does Yellowing Start?
Some nutrients are mobile within the plant and some are immobile. So whether yellowing starts on young (upper) or old (lower) leaves indicates the missing element:
- Yellowing on old (lower) leaves → mobile nutrient deficiency: nitrogen (uniform, pale yellowing), magnesium (interveinal yellowing, veins stay green), potassium (yellowing/scorch from leaf margins).
- Yellowing on young (upper) leaves → immobile nutrient deficiency: iron (interveinal yellowing, veins distinctly green), sulfur (uniform), zinc and manganese (interveinal).
Most Common Causes and Solutions
Nitrogen Deficiency
General, pale yellowing starting from lower leaves points to nitrogen deficiency. An application of Power NPK for balanced macronutrients and organic components provides rapid recovery.
Iron Deficiency (Iron Chlorosis)
The pattern where veins stay green and the area between them yellows on young leaves is very common, especially on calcareous, high-pH soils. Foliar chelated iron (FerroPlus) corrects it quickly; a lasting solution requires soil pH management.
Magnesium Deficiency
Interveinal yellowing on old leaves (veins staying green) indicates magnesium deficiency, corrected with magnesium supplementation. The potassium-magnesium balance matters.
Zinc and Manganese Deficiency
Shows as interveinal yellowing and small leaves on young growth; corrected with a foliar trace-element program.
Non-Nutritional Causes
Overwatering and root suffocation, root diseases, or salinity can also cause yellowing. In that case, irrigation and root-health management are needed, not fertilizer. For copper deficiency symptoms, see our copper deficiency guide.
Accurate Diagnosis: Soil and Leaf Analysis
Because symptoms can look alike, a definitive diagnosis is made with soil and leaf analysis. Learn to take a sample in our soil analysis guide, and have results interpreted by our agricultural engineers.
The first step in leaf yellowing is diagnosis, not a product: whether the yellowing is on young or old leaves is half of the right solution.
To solve yellowing for good, contact us; share your analysis results and we will identify the cause and build the right program together.
