Copper (Cu) & Cereal Production
Function of Copper
Copper (Cu) has an important role in the plant as an enzyme activator and as part of some of
the enzymes involved in respiration. It also has an indirect role in chlorophyll production. It is
very important in the plants reproductive stage of growth, and in cereals is important for ear
formation, floral fertility and grain development. Cu is fairly immobile in the plant, tending to
remain in the older leaves. This leads to deficiency symptoms most commonly occurring in
the younger growth. Cu increases plant sugar content, intensifies plant color and improves
flavor in fruit and vegetables.
Soil Copper (Cu) Index System
Soil Status
Soil Cu Range (mg/l)
1
<1.0
2
1.01 – 1.50
3
1.51 – 3.00
4
>3.00
Soil Analysis
The risk of Cu deficiency is high when the levels in heavy and light textured mineral soils are
less than 1mg/kg and 2 mg/kg of EDTA extractible Cu respectively. Where taking a plant
sample for Cu analysis take the tip of the youngest leaf as the whole plant may not show Cu
deficiency. Cu does not move easily from the older parts of the plant to the younger leaves
therefore best to sample youngest plant growth
Organic Matter
Soils high in organic matter maintain a tight hold on Cu and the availability is decreased.
Soils high in organic matter are, therefore, more likely to respond to addition of Cu.
Deficiency risk – Main Factors
1. Peat and organic soils especially after liming
2. Newly reclaimed and cultivated peat’s
3. Black ‘puffy’ soils with over 10% O.M.
4. Acid sands and heavily leached light soils
5. All soils with pH over 7.0 / Heavy Liming
6. Light soils @ <2.5mg Cu/kg –deficiency
7. Heavy soils <1.0mg Cu/kg –deficiency
8. Excessive applications of nitrogen or phosphate
9. Excess molybdenum / Dry , cold seasons
10. Cropping cereals after brassicas
Deficiency Symptoms
The symptoms of Cu deficiency are not as specific as those for most other trace elements. In
the early stages (GS 12-19) plants are stunted (short internodes), pale green in appearance
and the tips of the youngest leave become papery / white and leaf spiraling may occur. After
GS 20 – 29 plants are drawn and pale green in colour with white tips. The internodes are
long and the plants become flaccid and lodged. Symptoms may not appear until flag leaf or
even ear emergence. Affected ears are white and “rat tailed” in appearance with blind grains
in the ear.
Diagnosis & Treatment
Copper shortage in the plant can be diagnosed from soil analysis / history or where plants
show typical signs of Cu deficiency. Where crops are treated early the crop will make a good
recovery and only a slight reduction in grain yield but any delay in Cu application will result in
poor grain development and a large yield reduction. Cereal crops short in Cu will have brittle
straw resulting in heads breaking off easily.
Foliar application
Apply foliar Cu spray at early (GS 10 -21) to late tillering (GS 29). Late tillering to early boot
stage is the most effective time to apply Cu as a spilt application.
Winter cereals
Where there is a history of Cu deficiency, it is recommended to make an application close to
winter dormancy and a second application as soon as active spring crop growth
recommences.
Spring Cereals
On Cu deficient soils apply Cu at GS 10 – 21 and follow up with a second application at GS
31 – 49.
Interactions
Very high levels of phosphorus & Molybdenum may reduce Cu availability. High levels of N
application may cause more Cu uptake by the plant. The uptake of Cu can be either
increased or decreased, depending on the relationship with other micronutrients as aluminum,
zinc, iron and manganese.