Copper deficiencies in wheat are most obvious when swathing or dry combining the crops.
Copper-deficient wheat often has stem melacrosis, or a brownish, stunted appearance.
These stunted plants often occur in patches through the field.
Affected plants are delayed in maturity, have small, shriveled kernels and may have greater ergot infestation than healthy wheat.
This deficiency is most common on peat soils, or high pH sandy soils in Manitoba.
If you see deficient patches when combining, then a copper fertilizer should be included in the fertility plan, especially when cereal crops are grown.
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Winter wheat is particularly sensitive to copper deficiency on low copper soils.
In studies, wheat responded to foliar copper at sites located on sandy loam soil with less than 0.4 parts per million copper in the soil.
There was no response to applied copper at sites with clay loam to clay soils.
Application of copper may be a challenge for winter wheat. Most winter wheat is zero-tilled into standing stubble in the fall. But to optimize copper uptake by the crop, copper should be broadcast and incorporated into the soil to encourage root interception.
Uptake of copper occurs by root interception since copper is an immobile nutrient.
However with zero-till, rates of copper sulfate must be reduced to avoid seed toxicity. Some farmers are overcoming this by fertilizing copper in other crops where soil incorporation is possible or by broadcasting copper products before or after seeding in the fall.
Spring foliar applications may be successful for slight copper deficiencies, but may need to be repeated at tillering and before heading to overcome severe deficiencies. Foliar applications may be effective in salvaging the crop if copper deficiency is identified early through tissue sampling or observation of plant symptoms.
