Saline soil: white crust and scorched margins
Split salt from alkali. Salt is EC; alkali is pH and sodium.
- Look at the surface first: a thin white powder, or a hard crust.
- Seedlings come up in patches.
- Leaf margins look scalded.
- A light watering makes them worse — that is not drought.
- Salt is EC; alkali is pH and sodium — two jobs.
- If the well is salty too, ask whether the ditch still runs.
- Drought eases after water. Salt often wilts more after a light watering.
- Potassium does not need a white surface. Salt often pairs crust with patchy emergence.
- Powder or crust; after a light watering, better or worse. Write salt and alkali as two notes.
- Don’t flood a field with no ditch.
What you see in the field
Crouch and read the surface: a thin white powder, or a crust you can peel. Emergence is patchy, leaf margins scorch. A light watering makes wilt worse — that is not drought. Pull one plant from the poor patch and one from the green neighbour. A white crust is a clue to salt, not a prescription. Salt is EC; alkali is pH and sodium. If the well is salty too, ask whether the ditch runs before you irrigate.
Tap to enlarge. The caption says what to photograph. Missing field photos are marked as to-be-added.
Why it looks like this
Salt makes the soil water harder for the root to drink, so a light watering can worsen wilt. Sodium also breaks aggregates: mud when wet, a board when dry. Frequent light irrigation carries salt to the surface. Gypsum is for sodic alkali, not every white crust. Without a ditch, a heavy flooding lifts salt.
A sketch. Do not fertilise from the picture alone.Easy to mix up
Looks like “Potassium scorch”
Potassium scorch need not have a white surface, and roots can still drink. Salt often shows a crust or a dripper ring and worse wilt after a light watering.
Looks like “Drought”
Drought is dry soil that recovers when you water through. Salt is still wet and wilts more after a light watering. Read the surface and EC.
Do this / don’t do that
- 1Crouch and read the surface: powder, crust, a dripper ring. Photograph the poor patch next to the green neighbour. Split salt from alkali before the next bag.
- 2The ditch must run. Thin the feed first. Frequent light watering lifts salt; only a working ditch can leach. If the well is salty, ask about the ditch first.
- 3High pH and mud-then-board can discuss alkali amendment. Gypsum is not for every white crust. Rates live in the saline guides; confirm with a local station.
Don’t do this first
- Do not throw gypsum at every white crust.
- Do not flood without a ditch.
- Do not treat worse wilt after watering as more drought.
Rate range
| Crop × texture | Texture | Rate | Note |
|---|---|---|---|
| Wheat / maize / cotton | Any | Split the job: high EC → wash salt; high pH and high sodium → then gypsum | Rates from the local station. This page does not print bags. |
These are ranges. Confirm with your local extension station and the product label.
| Cell | Low | Mid | High |
|---|---|---|---|
| EC / total salt | Unlikely the salt story | Seedlings start to feel it | Patchy emergence, worse after watering |
| pH | Acid, not alkali | Near neutral | Alkali — ask sodium |
| Exchangeable sodium | Not sodic | Read with CEC | Structure fails; then gypsum |
| ESP | Sodium not occupying many seats | Structure starting to fail | Sodic |
One number example
White crust plus scorched margins at a dripper: thin the feed, open the ditch, then read EC. High pH, mud when wet and a board when dry look like alkali — gypsum needs drainage to move sodium. Do not throw gypsum at every white crust.
One bag from the thick crust, one from a clean emergence patch. In spring, read EC, pH and sodium.
Lesson video
2026-03-21 · 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