Main content area

Simultaneous measurements of ammonia volatilisation and deposition at a beef feedlot

Redding, M. R., Lewis, R., Shorten, P. R.
Animal production science 2019 v.59 no.1 pp. 160-168
air, ammonia, ammonium nitrogen, beef cattle, feedlots, greenhouse gas emissions, models, nitrogen, nitrous oxide, spectroscopy, statistics, temperature, traps, volatilization
The nitrogen (N) excreted at intensive livestock operations is vulnerable to volatilisation, and, subsequently, may form a source of indirect nitrous oxide (N2O) emissions. The present 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 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 2 weeks. Total volatilised ammonia amounted to 210 tonnes of NH3-N (127 g/, suggesting that the inventory volatilisation factor probably underestimated volatilisation in this case (inventory, 30% of excreted N; 65 g N volatilised/; a value of ~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). Net deposition within 600 m of the pen boundary represented only 1.7% to 3% of volatilised NH4+-N, between 3.6 and 6.7 tonnes N. Beyond this distance, deposition approached background rates (~0.4 kg N/ha.year).