Three long-term field experiments were established in the spring of 1978 and continued
through 1988 to evaluate corn (Zea mays L.) response to high Cu levels from Cu
rich swine manure and CuS04 applications. The field research was conducted on soils
with diverse properties, i.e., on a Bertie fine sandy loam (Aquic Hapludults), a Guernsey
silt loam (Aquic Hapludalfs), and a Starr-Dyke clay loam (Fluventic DystrochreptsTypic
Rhodudults). Three treatments in the long-term field experiments on the three
soils were a control, annual applications of eu as eu rich swine manure, and annual
applications of Cu as CuS04 equivalent to that in the manure. After the 11 years, 1109
mt ha-1 of wet Cu rich swine manure were applied for the manure treatment. The Cu
rich manure contained an average of 1316 mg Cu kg -I, An average of 325 kg Cu ha - 1
added to the soils from the manure application over the 11 years exceeded U.S.E.P.A.
guidelines for safe copper loading levels for cropland by 45 kg ha-1. Copper concentrations
in corn ear leaves were within the normal range of 3 to 20 mg kg-1 where the
325 kg Cu ha-1 were applied to the soil as either Cu rich manure or CuS04. Concentrations
of Cu in the grain were also in the normal range of 1 to 5 mg kg-1 where the
high level of the two Cu sources was applied to soils. There was no decrease in corn yield
on the three soils from application of either Cu source.
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