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Nitrogen deficiency: how to recognise and treat it

Deficiency

Nitrogen deficiency — Photo: Rasbak, CC BY-SA 3.0, Wikimedia Commons

Symptoms

Pale yellow leaves, first on the oldest, lowest leaves; the yellowing then spreads to younger foliage, sometimes with pink or reddish tints.
Spindly, stunted plants with smaller than normal leaves, shoots and fruit.
Older leaves may drop early.

Organic treatment

For a quick fix in the ground, nitrogen-rich poultry manure pellets at the rate on the label.
In pots, a general-purpose liquid feed.
For the long term, mulch with garden compost, manure or a plant-based soil conditioner, which releases a small, steady amount of nitrogen.

Chemical treatment

Sulphate of ammonia (21% nitrogen) or a slow-release coated urea at the label rate; too much nitrogen makes leaves dark green, stunts growth and washes into water.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Before feeding, rule out cold, frost or winter waterlogging, which also cause pale, poor spring growth.
Rain and watering wash nitrogen out — in pots the compost usually runs short after a few months, so feed container plants regularly.
Do not overfeed; most established trees and shrubs need no extra nitrogen, while fruit trees, roses and plants in containers or very sandy soil are the exceptions.

Sources

Figures checked against these sources.