Sensitivity of soil microbial processes to livestock antimicrobials

Authors: Miller, Daniel; MATTEO, D'ALESSIO - University Of Nebraska; SNOW, DANIEL - University Of Nebraska

Submitted to: Waste to Worth Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/21/2017
Publication Date: 5/16/2017
Citation: Miller, D.N., Matteo, D., Snow, D. 2017. Sensitivity of soil microbial processes to livestock antimicrobials. Waste to Worth Conference. http://articles.extension.org:80/pages/74357/proceedings-from-waste-to-worth-2017.

Interpretive Summary: Strong public concern that the overuse of livestock antimicrobials produce greater antibiotic resistance and pose a risk for human health have led to new regulations on the use of antimicrobials. Manure runoff containing trace levels of antimicrobial is usually applied to crop fields, but their impact on important soil processes--N transformations and decomposition--is largely unknown. A soil slurry study was conducted with three common livestock antibiotics to determine if any soil processes were affected. Decomposition products were monitored over several weeks. At highest concentrations tested (>5 ppm), monensin and sulfamethazine inhibited denitrification. Monensin also affected methane production, but sulfamethazine had no effect. Aerobic decomposition was unaffected by the three antimicrobials, but monensin at the highest level limited carbon dioxide production under anaerobic conditions. An increase in volatile fatty acids in monenesin treatments showed that incomplete decomposition had occurred. Although the concentrations of antimicrobials tested in these incubations were several orders higher than what is observed in the environment, we demonstrated that important soil microbial processes could be affected. Further study under more natural soil conditions are underway to better understand how antimicrobials affect important soil functions.

Technical Abstract: Strong public concern that the overuse of livestock antimicrobials produce greater antibiotic resistance and pose a risk for human health have led to new regulations on the use of antimicrobials. Manure runoff containing trace levels of antimicrobials is usually applied to crop fields, but their impact on important soil processes--N transformations and decomposition--is largely unknown. A soil slurry study was conducted with increasing concentrations of monensin, sulfamethazine, and lincomycin in order to assess their effects on denitrification and organic matter decomposition. Trace gas production and decomposition products were monitored over several weeks. At highest concentrations tested (>5 ppm), monensin and sulfamethazine inhibited denitrification (no N2O production). Monensin also affected methanogenesis (CH4 production), but sulfamethazine had no effect. Aerobic decomposition (CO2 production) was unaffected by the three antimicrobials, but monensin at the highest level limited CO2 production under anaerobic conditions. An increase in volatile fatty acids in monenesin treatments showed that incomplete decomposition had occurred. Although the concentrations of antimicrobials tested in these incubations were several orders higher than what is observed in the environment, we demonstrated that important soil microbial processes could be affected. Further study under more natural soil conditions are underway to better understand how antimicrobials affect important soil functions.