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Simultaneous measurements of ammonia volatilisation and deposition at a beef feedlot
The nitrogen (N) excreted at intensive livestock operations is vulnerable to volatilisation, and subsequently may form a source of indirect nitrous oxide (N2O) emissions. This study simultaneously investigated volatilisation and deposition of N at a beef feedlot, semi-continuously over a 129 day period. These data were examined relative to pen manure parameters, management statistics, and emission inventory calculation protocols. Volatilisation measurements were conducted using a single heated air sampling inlet, centrally located in a feedlot’s pen area, with real time concentration analysis via cavity ring-down spectroscopy and backward Lagrangian Stochastic (bLS) modelling. Net deposited mineral-N was determined via two transects of soil deposition traps with samples collected and re-deployed every two weeks. Total volatilised ammonia amounted to 210 Mg of NH3-N (127 g animal-1 day-1), suggesting that the inventory volatilisation factor probably underestimates volatilisation in this case (30 % of excreted N; 65 g N volatilised animal-1 day-1; a value of about 60 % of excreted N is indicated). Temperature contrast between the manure and air was observed to play a significant role in the rate of emission (R2 = 0.38; 0.46 Kendall’s tau; P < 0.05). Deposition within 600 m of the pen boundary represented only 1.7 to 3 % of volatilised NH4+-N, between 3.6 to 6.7 Mg N. Beyond this distance deposition approached background rates (about 0.4 kg N ha-1 year-1).
AN17310 Accepted 24 August 2017
© CSIRO 2017