Daily, Monthly, Seasonal, and Annual Ammonia Emissions from Southern High Plains Cattle Feedyards

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Abstract
Ammonia emitted from beef cattle feedyards adds excess reactive N to the environment, contributes to degraded air quality as a precursor to secondary particulate matter, and represents a significant loss of N from beef cattle feedyards. We used open path laser spectroscopy and an inverse dispersion model to quantify daily, monthly, seasonal, and annual NH3 emissions during 2 yr from two commercial cattle feedyards in the Panhandle High Plains of Texas. Annual patterns of NH3 fluxes correlated with air temperature, with the greatest fluxes (>100 kg ha−1 d−1) during the summer and the lowest fluxes (−1 d−1) during the winter. Mean monthly per capita emission rate (PCER) of NH3–N at one feedyard ranged from 31 g NH3–N head−1 d−1 (January) to 207 g NH3–N head−1 d−1 (October), when increased dietary crude protein from wet distillers grains elevated emissions. Ammonia N emissions at the other feedyard ranged from 36 g NH3–N head−1 d−1 (January) to 121 g NH3–N head−1 d−1 (September). Monthly fractional NH3–N loss ranged from a low of 19 to 24% to a high of 80 to 85% of fed N at the two feedyards. Seasonal PCER at the two feedyards averaged 60 to 71 g NH3–N head−1 d−1 during winter and 103 to 158 g NH3–N head−1 d−1 during summer. Annually, PCER was 115 and 80 g NH3–N head−1 d−1 at the two feedyards, which represented 59 and 52% of N fed to the cattle. Detailed studies are needed to determine the effect of management and environmental variables such as diet, temperature, precipitation, and manure water content on NH3 emissions. Copyright © 2011. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

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