Diagnose nutrient deficiencies from plant symptoms

Learn to read your plants. The key diagnostic principle is where symptoms appear first: older (lower) leaves indicate mobile nutrient deficiency (nitrogen, phosphorus, potassium, magnesium), while younger (upper) leaves indicate immobile nutrients (calcium, iron, sulfur, manganese).

Common Symptoms

• Nitrogen: General yellowing starting on older/lower leaves, stunted growth, pale green overall
• Phosphorus: Dark green leaves with purple or reddish tinting, delayed maturity
• Potassium: Brown, burnt leaf edges and tips (marginal scorch) on older leaves
• Calcium: Blossom end rot in tomatoes/peppers, distorted new growth
• Iron: Bright yellow between veins on youngest leaves, veins stay green
• Magnesium: Yellow between veins on older leaves with green "Christmas tree" pattern along midrib

Tips

• Multiple deficiencies, drought, disease, and herbicide damage can all look similar — visual diagnosis is a starting point, not a final answer
• By the time symptoms are visible, some yield loss has already occurred
• Most reliable for nitrogen, phosphorus, and potassium; micronutrient deficiencies are harder to distinguish visually
• Sources: West Virginia, Texas A&M, and University of Connecticut extension services