Application rates to correct copper deficiencies varies with source. Organic complexed or chelated copper sources are much more effective than inorganic sources of copper, for example, chelated copper versus copper sulfate or copper oxide. If the source is a copper oxide, the application rate to the soil should be much higher. Copper can be applied as organic compounds in the form of CuEDTA, copper ligninsulfonates and copper polyflavonoids. These compounds can be applied either to the soil at rates of about 1 to 5 pounds per acre or as foliar sprays at considerable lower rates.
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. Note that there can be complications if you mix copper materials with other fertilizers. Generally, it is better to apply copper either separately or as a chelated form in relatively low concentrations. The benefits of from 1.3 to 2.7 pounds of copper per acre have persisted undiminished for up to 35 years, according to information from western Australia. Go to feature stories index arranged by category.