Potassium: scorch from the old-leaf margin
Scorched margins plus a white crust: split salt from potassium first.
- Old leaf margins scorch first, as if singed, then roll in.
- Stems go soft; fruit is bland.
- The surface is not always white.
- A white crust plus scorch: sort salt from potassium first.
- Salt often has a crust and patchy emergence. Potassium often does not whiten the surface.
- Scorch right after potassium chloride is more chloride or salt. Potassium shortage is slower.
- Old margins scorch and roll in; stems soft; fruit bland. The surface is not always white.
- Don’t use potassium chloride on chloride-sensitive crops.
- Don’t spray a strong mix at noon.
- Don’t treat every scorched margin as potassium.
What you see in the field
Old-leaf margins scorch first and roll inward; stems soften; fruit is bland. Pick the worst old leaves and see whether the scorch walks in from the edge. The soil surface need not be white. A white crust plus scorched margins: split salt from potassium before you add potassium. Lay a scorched ridge next to a green neighbour. Salt often wilts more after a light watering; potassium shortage need not.
Tap to enlarge. The caption says what to photograph. Missing field photos are marked as to-be-added.
Why it looks like this
Potassium also moves from old leaves, so shortage scorches old margins first. Salt scorches too, but usually with a crust, a dripper ring, and worse wilt after a light watering. Mix the two and potassium will make the soil saltier. Read the surface and EC before potassium.
A sketch. Do not fertilise from the picture alone.Easy to mix up
Looks like “Salt scorch”
Salt often has a crust or a dripper ring and worse wilt after a light watering. Potassium scorch need not have a white surface.
Looks like “Hot dry wind”
Hot wind scorches a whole field, worse on the windward edge. Potassium walks in from old-leaf margins and a neighbour ridge still compares.
Do this / don’t do that
- 1See whether scorch starts on old-leaf margins and whether the surface is white. If those two do not line up, do not add potassium yet.
- 2A white crust: read EC with the saline guide. No crust and white roots: potassium with the label and a local station.
- 3Split potassium. This page does not print a bag count. Bland fruit alone is not a reason to add potassium.
Don’t do this first
- Do not add potassium at every scorched margin.
- Do not stack potassium on a white crust.
- Do not dump the whole rate at once.
Rate range
| Crop × texture | Texture | Rate | Note |
|---|---|---|---|
| Grain | Any | 5–15 kg/mu (about 75–225 kg/ha) once confirmed, no crust | Chloride-sensitive: potassium sulphate only |
These are ranges. Confirm with your local extension station and the product label.
| Cell | Low | Mid | High |
|---|---|---|---|
| Available K | Likely short | Watch the crop | Don’t add more |
One number example
Old-leaf margin scorch, no white crust, roots still white: potassium with a local station and the label, split. If the surface is already white, settle the salt question first. Do not pour potassium onto a crust.
Record the scorched leaf and whether the surface has a crust, as two notes.
Lesson video
2026-05-09 · Li Zeyu · For learning. Serious damage: local agronomist or a soil test.
For learning only. Fertiliser and pesticide decisions need a local agronomist and a soil test.
Not sure? Photograph the field to identify the problem