|Todd, Richard - Rick|
|Rhoades, Marty - West Texas A & M University|
|Parker, David - West Texas A & M University|
|Casey, Ken - Texas Agrilife Research|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2011
Publication Date: 7/1/2011
Citation: Todd, R.W., Cole, N.A., Rhoades, M.B., Parker, D.B., Casey, K. 2011. Daily, monthly, seasonal, and annual ammonia emissions from Southern High Plains cattle feedyards. Journal of Environmental Quality. 40:1-6.
Interpretive Summary: Ammonia that escapes as a gas from beef cattle feedyards can negatively impact sensitive ecosystems and degrade air quality when it reacts with other pollutants in the atmosphere. We measured ammonia emissions at two cattle feedyards on the southern High Plains continuously for two years. Annual patterns of ammonia emissions tracked closely with annual patterns of temperature, with the greatest ammonia loss during summer and least loss during winter. Average monthly loss of ammonia-nitrogen ranged from 0.07-0.08 lb per day for each animal in feedyards during January to 0.27-0.46 lb per day for each animal during September and October. The highest losses of ammonia occurred when one of the feedyards fed high crude protein diets that contained distiller's grains, a feed byproduct of ethanol production. When ammonia-nitrogen loss as a fraction of the amount of fed nitrogen was considered, average monthly fractional ammonia-N loss ranged from 19-24% to 80-85% of fed N at the two feedyards, with fractional loss least during winter months and greatest during summer months. Annually, ammonia-N emission rates were 0.25 and 0.18 lb per head per day at the two feedyards, which represented 59% and 52% of the nitrogen fed to cattle. Ammonia emissions are sensitive to crude protein in cattle diets, and emissions increased as crude protein increased above the level needed to meet the needs of cattle. More detailed studies are needed to determine the effect of management and environmental variables such as diet, temperature, precipitation, and manure water content on ammonia emissions.
Technical Abstract: Ammonia emitted from beef cattle feedyards adds excess reactive nitrogen to the environment, contributes to degraded air quality as a precursor to secondary particulate matter, and represents a significant loss of nitrogen from beef cattle feedyard systems. We used open path laser spectroscopy, coupled with an inverse dispersion model, to quantify daily, monthly, seasonal, and annual ammonia emissions over two years from two commercial cattle feedyards located in the Panhandle High Plains of Texas. Annual patterns of ammonia fluxes correlated with annual patterns of air temperature, with greatest fluxes (>100 kg/ha/d) during the summer and least fluxes (<15 kg/ha/d) during the winter. Mean monthly per capita ammonia-N emission rate (PCER) at one feedyard ranged from 31 g NH3-N/head/d during January to 207 g NH3-N/head/d during October, when increased crude protein because of distiller's grains in rations elevated emissions that month. Ammonia-N emissions at the other feedyard ranged from 36 g NH3-N/head/d during January to 121 g NH3-N/head/d during September. Monthly fractional ammonia-N loss ranged from 19-24% to 80-85% of fed N at the two feedyards, with fractional loss least during winter months and greatest during summer months. Seasonal PCER at the two feedyards averaged 60-71 g NH3-N/head/d during winter and 103-158 g NH3-N/head/d during summer, with PCER during spring and autumn intermediate between summer and winter values. Winter PCER was 62% of summer PCER. Annually, per capita ammonia-N emission rates were 115 and 80 g NH3-N/head/d at the two feedyards, which represented 59% and 52% of the nitrogen fed to cattle. Results were within the range of emission metrics found in other studies at cattle feedyards. Ammonia emissions are sensitive to crude protein in rations, and increased as crude protein increased above the level needed to meet the physiological needs of cattle. There was considerable variability both within and between the two feedyards, and more detailed studies are needed to determine the effect of management and environmental variables such as diet, temperature, precipitation, and manure water content on ammonia emissions.