Short-term Transformations of Copper in Copper-amended Soils1
- W. P. Miller,
- D. C. Martens and
- L. W. Zelazny2
Copper was added to three soils in the laboratory at a rate of 48 mg Cu kg−1 in the form of either CuSO4 or a swine (Sus scrofa domesticus) manure obtained from swine fed a high-Cu ration (equivalent to 100 Mg manure ha−1 containing 1060 mg Cu kg−1). In order to assess the potential transformations of the added Cu among various chemical forms in the soils, a sequential extraction methodology was used to determine types of soil-Cu associations in samples taken 1, 4, 12, and 29 d after Cu additions to moist soils. Copper added as high-Cu manure substantially increased water-extractable Cu in all soils through the entire incubation period, while CuSO4 additions resulted in higher exchangeable Cu levels through days 4 to 12. Most of the Cu added in both forms was recovered in “specifically adsorbed” forms, with 20 to 25 mg CuSO4-Cu kg−1 being Pb-extractable and 15 to 20 mg manure-Cu kg−1 being acetic acid-extractable throughout the incubation period. Significant amounts of Cu were also associated with soil organic matter (K4P2O7-extractable), more so when the Cu was added as high-Cu manure (10–15 mg Cu kg−1) than as CuSO4 (5 mg kg−1). Some additional added Cu was associated with Mn oxides and noncrystalline Fe oxides after 12 d of incubation, particularly in the two soils containing higher amounts of these oxides. These results suggest increases in short-term availability and mobility of Cu in these soils, particularly with high-Cu manure amendment, although longer-term reversion processes may reduce bioavailability over time.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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