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Tomato

Tomatoes are one of the most widely grown vegetable crops. They require rich, well-draining soil and consistent moisture. They are highly susceptible to calcium starvation causing Blossom End Rot, magnesium interveinal chlorosis, and aggressive pathogens like blights and wilt.

Confused about plant symptoms? Nutrient starvation can mimic aggressive fungal blights. Check our Symptom Disambiguation Guide to tell them apart.
Soil pH Alert: Many deficiencies are chemically locked due to soil acidity or alkalinity. Read our global Soil pH Interaction Guide to check if you need soil correction before applying fertilizers.
Nitrogen Deficiency
Moderate Severity

Nitrogen Deficiency

Nitrogen Deficientia

Key Visual Symptoms

Lower leaves turn a uniform pale light yellow. Stems become thin, fibrous, and may develop a purplish color due to anthocyanin accumulation. Yield and fruit size are drastically reduced.

Organic Remedy
  • Incorporate organic compost, well-rotted farmyard manure, or leaf mold during soil preparation.
  • Apply liquid organic drenches such as fish emulsion or compost tea during active growth stages.
Chemical Correction
  • Apply NPK 19:19:19 or top-dress with Urea at the vegetative stage.
  • Foliar spray with 1% Urea solution for quick rescue of yellowing foliage.
Learn More & Soil pH Notes
Calcium Deficiency
Severe Severity

Calcium Deficiency

Calcium Deficientia

Key Visual Symptoms

A water-soaked area appears at the blossom end (bottom) of the tomato fruit. This spot gradually enlarges, flattens, and turns into a dark brown or black, dry, leathery sunken scar. Affected fruits ripen prematurely and are unmarketable.

Organic Remedy
  • Maintain consistent, even soil moisture by mulching to ensure continuous calcium uptake.
  • Apply crushed eggshells, dolomite lime, or bone meal to the soil during planting.
Chemical Correction
  • Foliar spray with 0.5% Calcium Nitrate [Ca(NO₃)₂] or Calcium Chloride at active fruit set.
  • Apply agricultural gypsum (Calcium Sulfate) to soil to supply calcium without altering soil pH.
Learn More & Soil pH Notes
Magnesium Deficiency
Moderate Severity

Magnesium Deficiency

Magnesium Deficientia

Key Visual Symptoms

Interveinal chlorosis (yellowing between the veins) begins on older lower leaves. The main veins remain green, creating a sharp green network pattern. In severe cases, leaf margins curl upward and turn brittle.

Organic Remedy
  • Incorporate organic compost or dolomite limestone into acidic soils during bed preparation.
  • Apply seaweed extract which contains natural trace magnesium.
Chemical Correction
  • Foliar spray with Epsom Salt (Magnesium Sulfate, 10g/L water) at 10-day intervals.
  • Soil apply Magnesium Sulfate at 20-30 kg/acre.
Learn More & Soil pH Notes
Potassium Deficiency
Moderate Severity

Potassium Deficiency

Potassium Deficientia

Key Visual Symptoms

Older leaf margins turn yellow, then brown and papery, resulting in a distinct scorched border. Fruits develop uneven, blotchy ripening ('greenback' or yellow shoulder) and remain soft.

Organic Remedy
  • Apply organic wood ash or compost enriched with banana skins in the plant basin.
  • Mulch with straw crop residues to slowly release potassium into the soil.
Chemical Correction
  • Apply Sulfate of Potash (SOP) to avoid chloride toxicity, which tomatoes are sensitive to.
  • Spray 1% Potassium Nitrate (KNO₃) during peak fruit swelling.
Learn More & Soil pH Notes
Iron Deficiency
Early Severity

Iron Deficiency

Ferrum Deficientia

Key Visual Symptoms

Interveinal chlorosis develops on the youngest, emerging leaves at the top of the plant. The leaf blade turns pale yellow or white, while even the finest veins remain dark green. In severe cases, new leaves emerge completely bleached.

Organic Remedy
  • Apply organic humic acid or compost to lower soil pH and improve iron availability.
  • Use sulfur or organic peat moss to correct alkaline soil pH down to 6.0-6.5.
Chemical Correction
  • Foliar spray with 0.5% Chelated Iron (Fe-EDTA or Fe-EDDHA) for rapid leaf greening.
  • Apply Ferrous Sulfate (FeSO₄) to soil combined with compost to prevent binding.
Learn More & Soil pH Notes

Tomato Diagnostic Guide: Diseases vs. Deficiencies

Leaf and fruit yellowing in tomatoes can signify disease or nutrient starvation. Use this comparative key to distinguish them.

Early Blight Target Spots
Pathogen Spotting
Early Blight Target Spots
Blossom End Rot
Nutrient Starvation
Blossom End Rot
Key Indicators to Look For:
  • Leaf Position: Magnesium deficiency affects older lower leaves first, causing yellowing between green veins. Early Blight starts as spots on lower leaves but quickly develops concentric target rings.
  • Symmetry: Calcium Blossom End Rot is symmetric and isolated strictly to the blossom end of the tomato fruit. Fungal Buckeye Rot or Phytophthora creates irregular, asymmetric rings anywhere on the fruit.
  • Texture: Blossom End Rot lesions are flat, dry, and leathery. Fungal fruit rots are water-soaked, soft, and quickly turn the entire fruit mushy.

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Seasonal Outbreak Calendar

Track peak infestation and disease risk months by geographic region. Access the interactive dashboard to see what diseases are active this month.

Explore Disease Calendar

Featured Agronomy Guide

Read our comprehensive guide comparing plant nutrient deficiencies, infectious diseases, and pests.

Read Symptom Diagnosis Guide

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