Copper deficiency in wheat and barley: symptoms and fixes

What copper deficiency looks like

DPIRD (WA) describes the same pattern in wheat and barley. The youngest growth is hit first.

Before heads come out

• Patches of pale, wilted plants with dying new leaves, in an otherwise healthy green crop.
• Growing points die and leaf tips wither. Young leaves bleach and twist for up to half their length, while the base of the leaf can stay green.
• Old leaves stay green. Extra tillers may form but die early.
• Yara describes this as 'white tip': dry, white, twisted or curled tips on young leaves, with the whole plant stunted.

After heading

• Mild patches have wavy, disorganised heads. Bad patches have white heads and discoloured, late-maturing plants.
• Heads can be white and withered or empty 'rat-tails'. Mature wheat plants can look dull grey-black.
• Grain may be shrivelled. In wheat, heads with full grain can droop on weak stems.
• Yara notes heads can get trapped in the leaf sheath and come out with white tips and empty spikelets.

Why the heads are empty: copper is needed to form pollen. DPIRD says a shortage causes sterile pollen, poor grain set and high yield losses.

What else could it be

Soils and conditions at risk

• Sandy and gravelly soils. DPIRD says most WA soils were copper deficient in their natural state, and most sandy-surfaced soils needed copper and zinc when first cleared.
• Alkaline (high pH) soils. Incitec Pivot says copper becomes less available above pH 7.
• Recently or heavily limed paddocks. Plan lime rates with copper in mind on marginal soils.
• Dry topsoil. Copper barely moves in soil, so roots cannot reach it when the surface dries, especially in no-till paddocks.
• High nitrogen and zinc fertiliser can tip marginal paddocks into deficiency, as can root-pruning herbicides, particularly groups A and B (DPIRD). If you are also correcting zinc, read zinc deficiency in wheat.

How to confirm it

• Tissue test the youngest emerged blade. DPIRD's deficiency levels are below 1.5 mg/kg for wheat and below 1.6 mg/kg for barley.
• Whole-plant tests are a rough guide only. Take paired good and poor samples and confirm with a youngest-blade test.
• After heading, send affected heads with grain plus normal heads for grain analysis. Wheat grain below 1.2 mg/kg indicates deficiency (DPIRD).
• The DTPA soil test for copper is not well calibrated and is at best a rough guide (DPIRD). See reading a soil test.

Fixing it: soil or foliar copper

Foliar spray (this season)

• DPIRD says foliar copper works only in the current season, and does not work after flowering, because the crop needs copper before flowering to make pollen.
• Yara's cereal rate for YaraVita COPTRAC is 175–500 mL/ha from the two-leaf stage to second node (Z12–Z32).
• For dry northern NSW and Queensland springs, Incitec Pivot suggests 2% bluestone (copper sulphate) sprays at mid-tillering and just before booting where deficiency is known and little in-season rain has fallen, even if copper went on the soil. Bluestone is very corrosive; check with your sprayer's maker.
• Mixed trace-element liquids include EASY Liquids MICRO-SUL and YaraVita GRAMITREL. Follow the label.

Soil copper (lasts several years)

• Topdressing works poorly, because copper only reaches roots when the surface is wet. Mixing it through the topsoil or drilling it deeper helps (DPIRD).
• In long-term no-till, DPIRD suggests frequent small drilled or in-furrow doses.
• Seed treatment alone does not supply enough copper for the season (DPIRD).
• Copper Granules (25% Cu) are spread dry onto the soil, on their own or in blends; they do not dissolve fully, so cannot be sprayed. Incitec Pivot gives 8 kg/ha on light sands and 20–35 kg/ha on heavy clays, which may last 5 years or more, applied before sowing and worked in.
• Incitec Pivot does not recommend Copper Granules as an annual blend in narrow-row cereal starter, as too few granules land in each row. Compound starters that include copper, such as Summit Cereal (0.10% Cu) or MAP Trace (0.15% Cu) in Summit's product table, are an alternative to discuss with your agronomist.

Compare a soil and a foliar option side by side, or browse phosphorus starters and zinc products, many of which also carry copper. Always check with your agronomist before acting.