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Abstract
Information on nitrogen inputs and outputs for southeastern US pasture-based dairies is very limited. The first objective of this research was to estimate N losses via ammonia volatilization, nitrous oxide emissions, and nitrate leaching on two pasture-based dairies located in the Coastal Plain of Georgia (U.S.). The second objective was to create a one-year N balancefor the two dairies. Nitrogen inputs were obtained from farm records. Nitrogen outputs included milk export, ammonia volatilization, nitrous oxide emission, and nitrate leaching. A micrometeorological passive flux method measured ammonia. Nitrous oxide emissions were measured using closed chambers in the field. Cup lysimeters were installed at 1-m depth tomeasure NO3 leaching. Total N inputs were similar for both farms and so was N exported in milk when expressed as percentage of N inputs. However, ammonia and nitrate losses were very different between farms because of differences in N management practices.