- Inadequate copper leads to lower starch production, delayed flowering and pollen sterility. However, the symptoms are often not obvious until the deficiency becomes severe. Plants generally lack vigor. Leaves become light green or yellow and the tips become dry and turn brown. They shrivel, twist and break off from the plant. Younger leaves remain unrolled and growing points die. Roots become stunted and excessively branched. Eventually, the plant dies. In mature small grain plants, copper deficiency causes poor fill and partial head emergence.
- Plant analysis or soil testing can determine the amount of copper that the soil needs. Analysis of plant samples helps you understand what has happened, but does not reliably predict copper needs. Soil tests predict copper needs better, but are not available in all areas. The rarity of copper deficiency makes it difficult to justify the amount of research required to devise a soil test. Contact your local Extension Office to request a test for copper deficiency.
- To add copper content, apply the copper fertilizers to the soil. These include copper chelate, copper sulfate, cupric oxide and cuprous oxide. Copper chelate contains 13 percent copper. Copper sulfate and cupric oxide contain 25 percent and 75 percent copper, respectively. Cuprous oxide has the highest copper content at 89 percent. Use broadcast fertilizer before seeding. In small grains that are at the tillering stage, use foliar sprays containing copper sulfate.
- The amount of copper source to apply depends on the amount of elemental copper required to reach normal copper levels, the type of soil and the copper content of the source. Copper remains in the soil for many years because it becomes attached to organic matter in the soil. Keep annual applications of copper to less than 40 pounds per acre of elemental copper to avoid causing copper toxicity.
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