Copper impacts on corn, soil extractability, and the soil bacterial community

Abstract

Dairies use CuSO4 footbaths to control hoof infections, with Cu accumulation in agricultural soils realized when spent footbaths are disposed of in waste lagoons and subsequently used for irrigation. We investigated the effect of Cu applications (up to 1000 mg kg-1) to a Xeric Haplocalcid (Declo series) and a Typic Calciaquoll (Logan series) on corn (Zea mays L.) growth and Cu concentration, soil total and diethylenetriaminepentaacetic acid (DTPA)-extractable Cu, and the soil bacterial community diversity using ribosomal intergenic spacer analysis followed by cluster analysis. Copper application up to 250 mg kg-1 did not affect corn growth; at 500 mg Cu kg-1, corn growth was reduced by up to 80%. The 250 and 500 mg kg-1 Cu application rates increased corn Cu content grown in Declo soil, whereas the 500 mg kg-1 Cu application rate increased Logan soil corn Cu. Regardless of initial application rate, 60% to 75% of the added Cu was still plant available. Comparing DTPA-extractable Cu with corn Cu concentrations for the Declo and Logan soils, 130 or 220, and 215 or 300 mg kg-1 of DTPA-extractable soil Cu would be detrimental in terms of sheep and cattle dietary Cu intake, respectively. As Cu concentrations increased, bacterial diversity decreased, and species evenness remained high, suggesting that few phylotypes predominated within the ribosomal intergenic spacer analysis profiles. To prevent excessive corn Cu accumulation and negative impacts on the soil bacterial community, it is recommended that available soil Cu not exceed 130 mg kg-1 in agroecosystems associated with these soil series. Copyright © 2010 by Lippincott Williams & Wilkins.