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Molybdenum shortage: legumes fail to fix nitrogen, leaves twist

Acid soils lock molybdenum. Lime sometimes unlocks it.

Nutrient shortage
Speed
  1. Legume leaves distort and yellow; nodulation poor; plants thin.
  2. New leaves crinkle.
  3. Nitrogen shortage: old leaves even yellow, nodules may still be pink. Molybdenum shortage: nodules go dull first.
  4. Aluminium toxicity browns and bares the root tips; molybdenum shortage can keep the roots, but nodules do no work.
  5. Don’t pour nitrogen on yellow beans as the first move; molybdenum is a trace — doubling hurts.
  6. Foliar ammonium molybdate (after molybdenum is confirmed): A very small labelled amount, once from seedling to first flower. A small patch first. Too acid: lift pH first
  7. Name what you see before you feed.
  8. If leaves, roots and the surface disagree, stop.

What you see in the field

Legume leaves distort and yellow; nodulation poor; plants thin. New leaves crinkle.First the leaf position: new or old, even yellow or between the veins. If that does not match, do not fertilise yet. Pull one plant and read whether the roots are white, brown or foul.

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 “Nitrogen shortage”

    Nitrogen shortage: old leaves even yellow, nodules may still be pink. Molybdenum shortage: nodules go dull first.

  • Looks like “Aluminium toxicity”

    Aluminium toxicity browns and bares the root tips; molybdenum shortage can keep the roots, but nodules do no work.

Do this / don’t do that

  1. 1Legume leaves distort and yellow; nodulation poor; plants thin. New leaves crinkle.
  2. 2Test pH first. If too acid, lime a little per the acid guide. Foliar ammonium molybdate on the label — tiny rates, small patch.
  3. 3Don’t pour nitrogen on yellow beans as the first move. Use the range on this page only as a range. Confirm with a local station and the product label.

Don’t do this first

  • Don’t pour nitrogen on yellow beans as the first move; molybdenum is a trace — doubling hurts.

Rate range

Foliar ammonium molybdate (after molybdenum is confirmed)

A very small labelled amount, once from seedling to first flower. A small patch first

Too acid: lift pH first.

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

Available molybdenum

The nitrogen-fixing screw

Acid soil often runs low.

pH

Acid pins molybdenum

Too-acid bean land: lift pH first.

When you see Legume leaves distort and yellow; nodulation poor; plants thin. New leaves crinkle, test. Walk an S and mix — one hole is not the field.

Lesson video

2026-03-09 · 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