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Salt rising at the mulch edge: white frost along the film

The film is an umbrella, not a pickaxe.

Salty-alkali land
Speed
  1. A white ring at the film edge and hole; seedlings there scorch.
  2. Soil under the film may still be moist.
  3. Fertiliser grains are visible; rising salt is an even white crust at the film edge.
  4. Spray injury has a spray history; film-edge salt has a place pattern.
  5. Don’t sip-water the film edge; don’t replant and refertilise the salt ring.
  6. Where the seed sits: The wet zone under the film, skip the salt ring. After emergence, watch the film edge
  7. Name what you see before you feed.
  8. If leaves, roots and the surface disagree, stop.

What you see in the field

A white ring at the film edge and hole; seedlings there scorch. Soil under the film may still be moist.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.

A sketch. Do not fertilise from the picture alone.

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 “Fertiliser that never dissolved”

    Fertiliser grains are visible; rising salt is an even white crust at the film edge.

  • Looks like “Spray injury”

    Spray injury has a spray history; film-edge salt has a place pattern.

Do this / don’t do that

  1. 1Compare the worst plants with a neighbour ridge. Photograph whole plant, close-up and soil surface before you add fertiliser.
  2. 2Match roots, leaves and the soil surface to this guide. If they do not line up, do not copy a bag count.
  3. 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 sip-water the film edge; don’t replant and refertilise the salt ring.

Rate range

Where the seed sits

The wet zone under the film, skip the salt ring

After emergence, watch the film edge.

Irrigation

Water through under the film

A light watering is best at driving salt to the hole edge.

These are ranges. Confirm with your local extension station and the product label.

EC at the film edge

Where the salt was driven

Often higher than under the film.

When you see A white ring at the film edge and hole; seedlings there scorch. Soil under the film may still be moist, test. Mix several spots of the tilled layer; skip the edge and the manure heap.

Lesson video

2026-03-03 · 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