Copper, one of eight essential plant micronutrients, has a long history in agriculture. Its first recorded use was more than 250 years ago when growers learned that soaking seed grains in a weak solution of copper sulfate helped protect the plants from seed-borne fungi. Today, growers know even more about the benefits that copper delivers — and the problems that a copper deficiency can cause.
The primary factors influencing copper's availability to the plant are pH and organic matter. Alkaline soils with a pH of 7.5 or higher have less available copper. In acidic soils, deficiencies may occur if the organic matter content of the soil is high. Coarse, sandy soils are most prone to copper deficiencies, whereas heavy, clay-type soils are the least vulnerable.
This issue is important to note because copper helps facilitate respiration and photosynthesis in the plant and is important for plant metabolism. Copper helps in the formation of lignin, a complex organic polymer in the cell walls of the plants that helps make them rigid and woody. It’s the backbone of the stem that allows the plant to fight off high winds, storms, and other stresses. An inadequate amount of copper can lead to poor growth, delays in flowering and even plant sterility.
Symptoms of Copper Deficiency
Because copper is relatively immobile in soils, symptoms typically appear early in young growth. Generally, the symptoms first appear as cupping with slight chlorosis or yellowing of the leaf, particularly around the margins. Tips of the leaves may have a bluish-green tint. As the plant grows, the newer leaves will be smaller, and in some cases, the leaves will wilt. Older plants will appear stunted, with soft or limp stalks. When these symptoms are combined, a copper deficiency will significantly impact the plant’s formation and ultimate yield. Cereal grains are the most common crop to show copper deficiency, followed by corn. It’s rarely observed in soybeans.
Treating Copper Deficiencies
The best way to identify a potential copper deficiency is with a soil test combined with tissue testing. Copper is easily absorbed by plants with a pH between 5.5 and 6.5, assuming the soil is well-drained. Apply lime to raise the soil pH to 6 or above. To increase copper soil levels, add copper sulfate at a rate of three to six pounds per acre to a fertilizer blend.
Because we understand the importance of copper, Agnition includes copper in its Generate® and Commence® seed treatment lines to help deliver the benefits of copper to the plants – specifically, increases in photosynthesis, lignin and the metabolism of sugar in the plant. Moreover, our patented Microbial Catalyst® technology stimulates existing microbes by unlocking enzymes, making plants more efficient. This technology takes minerals such as copper and delivers them in a completely soluble and available form for plants and microbes.