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Potassium Deficiency

Potassium Deficientia

Basic Details

Description

Nutrient Info

Identify

Seasonal Calendar

Treatment

FAQs

How to Identify Potassium Deficiency on Tomato

Potassium Deficiency identification guide illustration

Visible 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.

Key Identification Checklist for Tomato Potassium Deficiency: 1. Marginal Leaf Scorch on Older Leaves: The outer edges of older, lower tomato leaves turn yellow (chlorotic) and rapidly advance to dry, papery, brown necrosis (leaf scorch) that curls upward. 2. Centripetal Chlorosis Pattern: The yellowing progresses inward from the scorched margins toward the center of the leaf blade, while the main veins and central tissue remain green longest. 3. Blotchy Ripening & 'Green Shoulders': Fruit quality drops severely. Tomatoes exhibit uneven color development with hard, persistent green or yellow shoulders around the stem end, and mealy, flavorless flesh. 4. Weak Straw-Like Stems & Fruit Drop: Plants have thin, weak stems prone to breaking under fruit weight, and flowers and small fruits drop prematurely.

About Potassium Deficiency

NamePotassium Deficiency

Description

Potassium deficiency in tomatoes impairs starch and sugar synthesis, resulting in poor fruit quality, uneven ripening, and reduced shelf-life. Tomatoes have high potassium demands during fruiting.

TypeDeficiency

Severity Level Moderate

Nutrient Role & Deficiency Cause

Affected Growth Stages

FloweringFruiting

Why It Happens

Potassium deficiency in tomatoes impairs starch and sugar synthesis, resulting in poor fruit quality, uneven ripening, and reduced shelf-life. Tomatoes have high potassium demands during fruiting.

Also Known AsK starvation, leaf scorch of tomato, blotchy ripening

Seasonal Outbreak Calendar

Outbreak risk and activity timeline for Potassium Deficiency based on seasonal climate patterns:

Active Window:May - October

Peak Outbreak:July - September

Critical Crop Stage:Fruit ripening stage

JanLow Risk

FebLow Risk

MarLow Risk

AprLow Risk

MayModerate

JunModerate

JulPeak Risk

AugPeak Risk

SepPeak Risk

OctModerate

NovLow Risk

DecLow Risk

Low Outbreak Risk

Active / Moderate Risk

High Risk / Peak Outbreak

Want to see this disease and others mapped across other regions? View Global Outbreak Calendar

Treatment & Correction Guide

Natural & Organic Methods

Screened Wood Ash (Potassium Carbonate - Acid Soils Only)

50–80 kg/acre (use only if soil pH is below 7.0) Incorporate into topsoil around drip line once per month Steady potash release over 2–4 weeks

Fermented Banana Peel & Liquid Seaweed Drench

100 ml fermented extract per 10 Liters water (1 Liter/plant) Drench root zone every 10–14 days from first flower opening Enhanced fruit coloring and sweetness in 7–10 days

Sulfate of Potash (SOP - OMRI Listed Organic Potassium)

15–20 kg/acre side-dressed along plant row Apply at flowering and repeat 30 days later Measurable leaf potassium elevation in 5–8 days

Chemical & Professional Control

Potassium Nitrate (13:0:45) Foliar Spray

5–8 g per Liter water (0.5–0.8%; 1.5 kg/acre in 200L) Spray every 7–10 days during fruit swelling and ripening Quick scorch arrest and fruit coloring in 3–5 days

Sulfate of Potash (0:0:50 SOP) Fertigation via Drip

3–4 kg/acre per week through drip system Start at flower bud stage and maintain through last harvest Elimination of blotchy green shoulder fruit in new sets

Monopotassium Phosphate (0:52:34 MKP) Foliar Spray

4–5 g per Liter water Apply at early fruit set and 14 days later Strengthens fruit firmness and uniform red color

Frequently Asked Questions

Why do the edges of tomato leaves turn brown and crispy?

Marginal leaf scorch is the signature symptom of potassium deficiency. Potassium regulates water balance and stomatal opening; when deficient, leaf margins dehydrate, turn chlorotic yellow, and quickly burn to a papery brown.

What causes green shoulders on ripe tomatoes?

Potassium deficiency impairs lycopene (red pigment) synthesis during fruit ripening, particularly when tomatoes are exposed to direct sunlight and high temperatures, resulting in hard yellow or green tops on ripe red tomatoes.

What is the best foliar spray for tomato potassium deficiency?

Water-soluble Potassium Nitrate (13-0-45) at 5–8 g/L or Monopotassium Phosphate (0-52-34) at 4–5 g/L. Foliar potassium is absorbed rapidly through the tomato leaf cuticle, showing benefits within 3–5 days.

Can I use wood ash to treat potassium deficiency in tomatoes?

Yes, wood ash contains 5–7% potassium carbonate. However, it is very alkaline and raises soil pH. Use it only if your soil pH is below 6.8, applying 50–80 kg/acre, and avoid contact with wet tomato leaves.

When is potassium demand highest in tomato plants?

Potassium uptake peaks during fruit swelling and color break. A tomato plant takes up more potassium than nitrogen during this period to fill fruit sugars, maintain firmness, and develop uniform red pigmentation.

Remedy Disclaimer & Safety Notice

This disease guide is for educational screening purposes only. Pathogen behavior, severity, and host susceptibility can vary dramatically based on seed variety, weather conditions, and regional microclimates. Chemical pesticides and organic treatments are subject to strict regional environmental regulations and registration mandates. Please verify all chemical registrations and review manufacturer safety labels carefully with local certified agronomists or agricultural extension service offices before applying.

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