Diagnosing copper deficiency in wheat

Most soils in Western Australia (WA) were copper deficient in their natural state. Copper is essential for pollen formation and has a role in formation of chlorophyll and lignification (cell wall strength). Deficiency causes sterile pollen, which, in turn causes poor grain formation and high yield losses.

What to look for

Paddock

Before head emergence deficiency shows as areas of pale, wilted plants with dying new leaves in an otherwise green healthy crop.
After head emergence mildly affected areas have disorganised wavy heads. Severe patches have white heads and discoloured late maturing plants.
Symptoms are often worse on sandy or gravelly soils, where root pruning herbicides have been applied and recently limed paddocks.

Plant

Youngest growth is affected first.
First sign of copper deficiency before flowering is growing point death and tip withering, and/or bleaching and twisting up to half the length of young leaves.
Base of the leaf can remain green.
Old leaves remain green, but paler than normal.
Tiller production may increase but die prematurely.
Mature plants are dull grey-black in colour with white or stained empty or 'rat-tail' heads.
Grain in less severely affected plants may be shrivelled. Heads with full grain droop due to weak stems.

Where does it occur?

Soil type

Dry conditions

Most sandy surfaced soils required copper and zinc when initially cleared for agriculture.
Copper is relatively immobile in soil and can become unavailable to crops in dry soil.
Where copper soil levels are marginal, deficiency can be induced by applications of lime, increased nitrogen fertiliser and zinc fertiliser.
The use of root-pruning herbicides, particularly groups A and B can induce copper deficiency.

Management strategies

Spraying foliar

Foliar spray (only effective in the current season) or drilled soil fertiliser.
Copper foliar sprays are not effective after flowering as sufficient copper is required pre-flowering for pollen development.
Mixing copper throughout the topsoil improves availability due to more uniform nutrient distribution.
As copper is immobile in the soil topdressing is ineffective, only being available to the plant when the topsoil is wet.
In long term no-till paddocks frequent small applications of copper via drilled or in-furrow application reduces the risk of plant roots not being able to obtain the nutrient in dry seasons.
Copper drilled deep increases the chances of roots being able to obtain enough copper when the topsoil is dry.
Copper seed treatment is insufficient to for plant requirement in the current season.

How can it be monitored?

Tissue test

A DTPA soil test is not sufficiently calibrated and provides at best a rough guide to soil copper status.
Whole-top plant test provides a rough guide if paired good/ poor samples are taken, but this should be confirmed with a youngest emerged blade (YEB) test.
YEB levels below 1.5 milligrams per kilogram (mg/kg) indicate copper deficiency.
Copper deficiency may be confirmed by submitting samples of affected heads containing grain and unaffected heads for grain analysis.
Grain levels below 1.2mg/kg indicate copper deficiency.

Further information

Plant nutrition [1]