Diagnosing nutrient deficiencies
Identify nitrogen, phosphorus, potassium, calcium, magnesium, and iron deficiencies from leaf symptoms and confirm with soil tests.
12 min · advanced
You will learn
- Distinguish mobile and immobile nutrient deficiency patterns
- Recognize visual symptoms of N, P, and K deficiency
- Distinguish nutrient problems from watering and pH issues
Mobile vs. immobile nutrients
Mobile nutrients like nitrogen, phosphorus, and potassium move within the plant, so deficiency appears on older leaves first as the plant remobilizes them to new growth. Immobile nutrients like calcium, iron, and boron cannot relocate, so symptoms show on young leaves and growing points. This pattern narrows the suspect list before you test or treat.
Macronutrient symptoms
University of Minnesota Extension describes nitrogen deficiency as yellowing of older leaves and stunted, pale growth. Phosphorus deficiency shows as dark green or purplish older leaves and delayed maturity. Potassium deficiency appears as browning or scorching along older leaf margins and weak stems. These symptoms overlap with drought and disease, so consider growing conditions and soil test history together.
Calcium and magnesium
Calcium deficiency causes blossom end rot in tomatoes and peppers, and distorted new leaves on many crops. It often reflects inconsistent watering rather than low soil calcium. Magnesium deficiency shows as interveinal chlorosis on older leaves while veins stay green. A soil test confirms whether amendments are needed.
Iron and micronutrients
Iron deficiency presents as interveinal chlorosis on young leaves, common in alkaline soils or waterlogged roots. Lowering pH or foliar iron sprays provide relief. Zinc and manganese show similar patterns at different pH extremes. Confirm with soil tests when possible because excess of one nutrient can block uptake of another, mimicking deficiency.