High moisture and high temperature soils also tend to have exaggerated copper deficiency symptoms. Regarding application rates to correct copper deficiencies -this varies with source. The lowest rates of application are about 0.2 pounds of copper per acre of chelated materials applied to the foliage. Plant tissue is sensitive to copper and toxicity can be a problem when high concentrations occur in the soil. If the source is a copper oxide, the rate applied to the soil should be much higher.
Annual applications are usually necessary on high organic soils.
On mineral soils, copper toxicity to plants can be a problem if application of fertilizer is excessive. Organic complexed or chelated copper sources are much more effective than inorganic sources of copper, i.e., chelated copper versus copper sulfate or copper oxide. Note that there are some complications in mixing copper materials with other fertilizers. It is generally better to apply copper either separately or as a chelated form -in relatively low concentrations. Soil applied copper will generally have long-lasting residual effects.