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Sampling for a soil test: how to miss the truth

One spadeful from the ditch bank is not this field.

Other
Speed
  1. Soil taken badly poisons every later decision.
  2. One hole, a manure heap, a field edge — none of those is the field.
  3. Labs make mistakes; more often you took soil from the wrong spot.
  4. Leaves can point a direction; they cannot set a rate.
  5. Don’t dig one hole; don’t take soil from the manure pile; don’t mix pan and topsoil in one bag.
  6. How deep to take soil: Dry crops: commonly 0–20 cm. Fruit trees: along the drip line of the crown, follow local advice
  7. Name what you see before you feed.
  8. If leaves, roots and the surface disagree, stop.

What you see in the field

Soil taken badly poisons every later decision. One hole, a manure heap, a field edge — none of those is the field.Walk the worst strip and compare a neighbour. Photograph the whole plant, a close-up and the soil surface. If those three do not line up, do not rush a bag. Lab numbers have to match the field.

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 “A lab mix-up”

    Labs make mistakes; more often you took soil from the wrong spot.

  • Looks like “Reading the leaf as a soil test”

    Leaves can point a direction; they cannot set a rate.

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 dig one hole; don’t take soil from the manure pile; don’t mix pan and topsoil in one bag.

Rate range

How deep to take soil

Dry crops: commonly 0–20 cm

Fruit trees: along the drip line of the crown, follow local advice.

How many spots

Mix 8–15 spots

The bigger the field, the more spots.

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

pH / organic matter / salt

Read these three first

Then nitrogen, phosphorus, potassium and the micronutrients.

A field check

Which leaves, the roots, the soil surface

Compare a healthy neighbour plant.

When you see Soil taken badly poisons every later decision. One hole, test. Mix several spots of the tilled layer; skip the edge and the manure heap.

Lesson video

2026-03-04 · 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