Nitrogen: old leaves yellow, new leaves still green
Yellow old leaves, white roots. If new leaves yellow too, think sulphur or iron.
- Lower old leaves yellow evenly, new leaves at the top still green, washed roots still white — that looks like nitrogen.
- If new leaves yellow too, think sulphur or iron.
- Don’t pour urea on black, smelly roots.
- Iron yellows new leaves with green veins. Nitrogen yellows old leaves more evenly.
- Waterlogging wilts by day and smells at the root. Nitrogen still has white roots.
- Lower old leaves yellow, new leaves green, plants thin, few tillers. White roots look like nitrogen.
- If new leaves yellow too, think sulphur or iron first.
- Urea top-dress (white roots, nitrogen confirmed): Maize at jointing or leafy vegetables in flush: commonly 5–15 kg/mu (about 75–225 kg/ha), split; sand at the low end plus one extra split. Foliar nitrogen is first aid, not a soil replacement
- Split nitrogen only while roots are white.
- Don’t dump the year on sand.
What you see in the field
Read which leaves are yellow. Old leaves evenly yellow, new leaves still green, and washed roots still white: that looks like nitrogen. If new leaves yellow too, think sulphur or iron. Black, smelly roots or standing water: do not call it nitrogen. Pick old leaves and a plant from the yellow ridge and from the green neighbour. If leaf position does not match, do not rush urea.
Tap to enlarge. The caption says what to photograph. Missing field photos are marked as to-be-added.
Why it looks like this
Nitrogen moves from old leaves to new ones, so shortage yellows old leaves first. Waterlogging yellows too, but roots are usually black. Sulphur yellows the whole plant; iron yellows new leaves with green veins. Read leaf position and root colour before nitrogen. Urea is not the name of every yellow leaf.
A sketch. Do not fertilise from the picture alone.Easy to mix up
Looks like “Iron on new leaves”
Iron yellows new leaves with veins still green. Nitrogen yellows old leaves first while new leaves stay green. Mix the position and the fertiliser goes the wrong way.
Looks like “Waterlogging yellow”
Waterlogging wilts by day and blackens roots. Nitrogen shortage often still has white roots. Read the root first.
Do this / don’t do that
- 1Read leaf position and roots. Old leaves evenly yellow, new leaves green, roots white: then nitrogen is on the table. If position does not match, do not add urea.
- 2Rule out waterlogging and spray injury. Standing water or black roots: drain first; nitrogen cannot enter.
- 3Rates follow the label and a local station, split. This page does not print a bag count. Feed only when roots are white and leaf position matches.
Don’t do this first
- Do not pour urea on black roots.
- Do not call every yellow leaf nitrogen.
- Do not treat yellow new leaves with green veins as nitrogen.
Rate range
| Crop × texture | Texture | Rate | Note |
|---|---|---|---|
| Maize / leafy vegetables | Sand | Urea 5–15 kg/mu (about 75–225 kg/ha), split; sand at the low end | White roots only. Foliar is first aid. |
These are ranges. Confirm with your local extension station and the product label.
| Cell | Low | Mid | High |
|---|---|---|---|
| Alkaline-hydrolysable N | Likely short this season | Watch the crop | Lodging risk |
One number example
Maize with evenly yellow old leaves, green new leaves and white roots: check waterlogging and crowding first, then nitrogen with a local station and the label. Black, smelly roots: drain first, do not pour urea.
Note the lower yellow leaves and the green top, then sample the plough layer.
Lesson video
2026-04-11 · 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