Diagnosing copper deficiency in barley

Most soils in Western Australia 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 and most severely.
The first sign of copper deficiency before flowering is growing point death and tip withering, and/or bleaching and twisting of up to half the length of young leaves.
The base of the leaf can remain green.
Old leaves remain green and seemingly healthy.
Tiller production may increase but they die prematurely.
Heads may be white and withered or have a rat-tail appearance.
Maturity is delayed and very late tillers may be present.
Stems are weaker, although in less severe plants heads may be more erect. Severely deficient plants have few immature heads on weak and dirty stems.

Where does it occur?

Dry conditions

Spraying herbicide

With the exception of loam or clay salmon gum or York-gum soils, most soils required copper and zinc when cleared for agriculture.
Copper persists in soil but is relatively immobile and can become unavailable to crops in dry soil particularly in no-till systems.
Copper deficiency can be induced by heavy liming; increased plant nitrogen status; use of zinc fertiliser; and use of root-pruning herbicides, particularly groups A and B.

Management strategies

Spraying foliar

Soil application

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 fertile pollen development.
As copper is immobile in the soil, topdressing is of little value, only being effective when the topsoil is wet.
Mixing copper throughout the topsoil makes it more likely that roots can intercept the nutrient because soil at depth stays moist longer.
In long term no-till paddocks fertiliser use via in-furrow application or seed treatment reduces the risk of plant roots not being able to obtain enough copper in dry seasons.
Copper seed treatment is insufficient to for plant requirement in the current season.

How can it be monitored?

Soil test

Tissue test

DTPA soil test and whole top plant test provide a rough guide for copper status.
Use youngest emerged leaf to tissue test for copper levels with levels less than 1.6 milligrams per kilogram (mg/kg) indicating copper deficiency.
Copper deficiency may be confirmed by grain test after sampling affected heads containing grain and unaffected heads from the crop.

Further information

Plant nutrition [1]