Leaching salt: irrigation without drainage just drives the salt up
A flush needs a way out.
- After a big irrigation the edge is whiter, the neighbour starts to frost, the water table rises.
- The ditch mouth must run.
- Dry soil needs a watering; washing salt is a with-in-and-out job of its own.
- After a wash the field edge is saltier — salt was driven there, not undissolved fertiliser.
- Don’t flood against a blocked ditch; don’t dump brine onto a neighbour with no outlet.
- A drain: Water can go in, and can leave. This is the premise
- Name what you see before you feed.
- If leaves, roots and the surface disagree, stop.
What you see in the field
After a big irrigation the edge is whiter, the neighbour starts to frost, the water table rises. The ditch mouth must run.Squat on the whitest, worst strip and scrape the crust. Compare with a neighbour that is still green. White crust plus scorched margins count; wilt without a crust may just be drought. Note whether the ditch actually runs.
Tap to enlarge. The caption says what to photograph. Missing field photos are marked as to-be-added.
Why it looks like this
The field looks like this because the root cannot take water or nutrients the usual way. Fix the soil condition first — drainage, salt, acidity, compaction or a salt of fertiliser — then a thin feed. Rates live in the range on this page; confirm with a local station and the label.
Easy to mix up
Looks like “Drought, no water”
Dry soil needs a watering; washing salt is a with-in-and-out job of its own.
Looks like “Fertiliser put on badly”
After a wash the field edge is saltier — salt was driven there, not undissolved fertiliser.
Do this / don’t do that
- 1Compare the worst plants with a neighbour ridge. Photograph whole plant, close-up and soil surface before you add fertiliser.
- 2Match roots, leaves and the soil surface to this guide. If they do not line up, do not copy a bag count.
- 3Use the rate range on this page only as a range. Confirm with a local station and the product label.
Don’t do this first
- Don’t flood against a blocked ditch; don’t dump brine onto a neighbour with no outlet.
Rate range
A drain
Water can go in, and can leave
This is the premise.
How much water to wash salt
Follow the station and the water quality
Don’t irrigate night after night on your own.
These are ranges. Confirm with your local extension station and the product label.
When you see After a big irrigation the edge is whiter, test. Write the field and the date on the bag.
Lesson video
2026-04-08 · 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