Potassium deficiency
Yellow-brown scorching along the margins of the older leaves, weak lodging-prone stems, and poorly filled grain or fruit.
- Nutrient type
- Primary (macro)
- Mobility in plant
- Mobile
- Symptoms start on
- Old (lower) leaves
- Most at risk
- Light soils, heavy feeders
Overview
Potassium regulates water inside the plant, thickens cell walls and moves sugars into grain and fruit. It is the nutrient of sturdiness and stress tolerance — a well-supplied crop stands up to drought, resists lodging and fills its produce; a short one does none of these well even when nitrogen and phosphorus are fine.
The classic symptom is a scorch: the margins and tips of the older leaves yellow and then dry to a brown, burnt edge, while the centre of the leaf and the midrib stay green. Because potassium is mobile, this always starts on the oldest leaves. Heavy feeders like banana, potato, sugarcane and cotton, and light or sandy soils, are where it shows most.
How to spot it
- Margins and tips of the older, lower leaves yellow first, then dry to a brown scorched edge — the middle of the leaf and the midrib stay green.
- In broadleaf crops (cotton, potato, grapes) the scorch is a rim of dead tissue around an otherwise green leaf; in cereals the leaf tips and edges dry back.
- Stems are weak and thin, and the crop lodges (falls over) in wind or rain more than a healthy one.
- Grain, tubers and fruit fill poorly and are smaller; the crop wilts in midday heat even when the soil is not dry.
Why it happens
- Light, sandy and red soils hold little potassium; it also leaches on these soils under heavy rain or irrigation.
- High-yield, heavy-feeding crops (banana, sugarcane, potato, cotton) remove large amounts of potassium and exhaust the soil supply fast.
- Repeated cropping where only nitrogen and phosphorus are replaced, so potassium is mined out season after season.
- Very high magnesium or calcium in the soil can block potassium uptake even when soil K looks adequate.
Confirm before you spend
- The scorched margin around a green leaf centre, starting on the old leaves, is characteristic — but a salt/fertiliser burn also scorches margins, so check that the pattern follows the oldest leaves.
- A soil test tells you the field’s status; potassium-hungry crops like banana and potato are worth testing before every cycle because they draw it down so fast.
How to correct it
- Apply muriate of potash (MOP, 60% K₂O) or sulphate of potash (SOP) to the soil per the crop’s recommendation — split it for long-duration heavy feeders (banana, sugarcane) rather than one dose.
- For a fast response on a scorching crop, spray 1–2% potassium (e.g. 1% MOP or SOP, roughly 1 kg in 100 litres) on the foliage and repeat after 10–15 days.
- On chloride-sensitive crops (tobacco, some fruit) and where salinity is a concern, use sulphate of potash rather than muriate of potash.
- The per-hectare dose varies widely by crop — a banana or potato crop needs several times what a cereal does — so follow the specific package of practices.
Prevent it coming back
- Replace potassium every season for heavy feeders, and return crop residues and FYM — straw and banana pseudostem are rich in potassium.
- On light soils, split potassium into two or more doses to cut leaching loss, as you would for nitrogen.
- Test the soil regularly for potassium-hungry crops so you top it up before the crop mines it below the critical level.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
The edges of my leaves are burnt but the middle is green. What is it?
That margin-scorch-with-green-centre, starting on the older lower leaves, is the classic sign of potassium deficiency. Confirm it is following the oldest leaves (not random leaves, which would suggest a fertiliser or salt burn) and correct with a potash application plus a foliar spray for quick relief.
Why does my banana/potato keep running short of potassium?
Because they are very heavy feeders — they remove more potassium than almost any other crop. On light soils, one basal dose is not enough; split the potash across the season and return residues (banana pseudostem, potato haulm) so you are not mining the soil down every cycle.
MOP or SOP — which should I use?
Muriate of potash (MOP) is cheaper and fine for most field crops. Use sulphate of potash (SOP) for chloride-sensitive crops such as tobacco and certain fruits, on saline soils, and where the extra sulphur is useful. Both correct the deficiency; the choice is about the chloride and the crop.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.