Corn responses to high levels of copper application as copper rich pig manure

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Virginia Polytechnic Institute and State University

The use of copper (Cu) in pig production to stimulate growth and improve feed efficiency is presently being questioned due to the potential environmental hazards associated with the repeated disposal of the resulting Cu rich manure in agricultural land. Results of field experiments conducted on three diverse Virginia soils indicated that the long-term application of Cu as either copper sulfate or Cu rich pig manure, even at high application rates (average application rate for 9 years was 108 metric tons of manure ha⁻¹ year⁻¹ or 32 kg Cu ha⁻¹ year⁻¹), had no adverse effects on corn yields. Copper levels in corn grain and leaf tissue were not increased by the nine annual applications of Cu rich manure or CuSO₄ , except for a slight increase in Cu concentration in corn grain from CuSO₄ application on only one soil. Copper concentrations in all plant tissues were well within normal ranges for all treatments at all sites. Corn grain yields were not decreased by Cu application on any of the three soils.