Phosphorus shortage: seedlings purple, stiff, short of roots
Cold and acid soils lock phosphorus even when the bag was applied.
- Seedlings purple, dark green, stunted, few roots.
- Warmth does not restart them.
- Nitrogen shortage is yellow; phosphorus shortage is dark green with purple and a stall.
- Chill can purple too and eases when it warms; phosphorus shortage still stalls after a warm spell, worse on acid land.
- Don’t broadcast P on untested pH; don’t heap lime and phosphate the same day.
- Phosphorus by the root (after shortage is confirmed): On acid soil, band calcium-magnesium phosphate. Seedling foliar potassium dihydrogen phosphate: labelled lower rate as first aid. Broadcasting the whole field is worse than putting it where the root can touch it
- Name what you see before you feed.
- If leaves, roots and the surface disagree, stop.
What you see in the field
Seedlings purple, dark green, stunted, few roots. Warmth does not restart them.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.
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-yellow seedlings”
Nitrogen shortage is yellow; phosphorus shortage is dark green with purple and a stall.
Looks like “Chill purple”
Chill can purple too and eases when it warms; phosphorus shortage still stalls after a warm spell, worse on acid land.
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 broadcast P on untested pH; don’t heap lime and phosphate the same day.
Rate range
Phosphorus by the root (after shortage is confirmed)
On acid soil, band calcium-magnesium phosphate. Seedling foliar potassium dihydrogen phosphate: labelled lower rate as first aid
Broadcasting the whole field is worse than putting it where the root can touch it.
These are ranges. Confirm with your local extension station and the product label.
Phosphorus the crop can use
pH moves it a lot. Low, and seedlings go purple and stall.
When you see Seedlings purple, test. Walk an S and mix — one hole is not the field.
Lesson video
2026-03-25 · 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