An environmental assessment of cattle manure systems in the northern great plains

Nitrogen, phosphorus and carbon emissions from livestock systems have become an important national and international concern. Our objective was to use process level simulation to explore long-term differences among manure and fertilization treatments of corn produced to feed finishing cattle in the Northern Plains region of the United States. The Integrated Farm System Model was evaluated in representing the performance and nutrient losses of corn production using cattle manure without bedding, manure with bedding, urea and no fertilization treatments. Two-year field experiments conducted near Clay Center, NE, Brookings, SD and Fargo, ND provided observed emission data following field application of these treatments. In a comparison of model simulated emissions to observed values, predicted daily emissions from field-applied manure or fertilizer were not highly correlated to observed values, but the model appropriately represented long-term annual emissions of methane, ammonia and nitrous oxide. Simulation of corn production systems over 25 years of weather showed greater ammonia emission, nitrate leaching loss, and soluble P loss from feedlot and bedded manure compared to the use of inorganic fertilizers, but life-cycle fossil energy use and greenhouse gas emission were decreased. Projected climate change by mid-century gave a small increase in simulated feed production in North Dakota with small decreases in South Dakota and Nebraska. Climate change affected the three production systems similarly, so production and environmental impact differences among the fertilization systems under future climate were similar to those obtained under recent climate.