- Animals: poultry
- Animal Production: feed additives, manure management
- Crop Production: nutrient cycling, organic fertilizers
- Soil Management: nutrient mineralization, soil analysis, soil chemistry, soil microbiology
Agricultural soils are exposed to veterinary antibiotics when manure fertilizers containing residual active compounds are spread as fertilizers or fertilizer amendments. While there is evidence to suggest that trace antibiotics in soil may significantly alter the microbial community structure or function, a comprehensive assessment of nitrogen cycle dynamics in antibiotic amended soils is currently lacking. Because sustainable fertilizer practices are based on known parameters of soil nitrogen cycle variation, microbial inhibition or delayed activity caused by antibiotics may undermine the ability of modeling tools to make strong fertilizer management recommendations, leading to reduced fertilizer use efficiency and increased inputs of pollutant N species, including N2O and NO3-, to environmental reservoirs. The objective of this dissertation research is to fully assess the impact of narasin, an anticoccidioidal drug commonly administered to poultry and livestock, on nitrogen dynamics at a field site near Milford, Delaware. Dose-response and time-series curves for nitrogen redox reaction rates, the production of N2O, and the accumulation of NO3- will be constructed from a set of complimentary lab and field experiments using environmentally relevant concentrations of narasin (0.001 – 1.0 ug/kg). Results will be statistically compared to determine the reliability of incubation tests as a predictor of in-situ changes to the N-cycle caused by trace narasin and applied to a STELLA model to evaluate the field-level significance at different exposure levels.
Project objectives from proposal:
A comprehensive assessment of the interactions between antibiotics and microbial nitrogen cycle is essential to improving nitrogen fertilizer management strategies to achieve optimal fertilizer use efficiency and reduce non-point source NO3- and N2O pollution. The primary objectives of our research are to:
1. Quantify the impact of environmentally relevant concentrations of the anticoccidioidal agent, narasin, on the rate of mineralization, nitrification, denitrification, N2O emissions, and potential NO3- losses in an Ultisol soil used for intensive production of corn and soybeans.
2. Develop a dose-response model for the rate of mineralization, nitrification, denitrification, N2O emission, and potential NO3- leaching as a function of antibiotic dose, soil moisture, and time.
3. Test the accuracy of the dose-response model derived from laboratory experiments by conducting replicate experiments in the field.
4. Evaluate the significance of antibiotic-altered soil nitrogen to estuarine nitrogen loading at the field site.