Location: Livestock Nutrient Management ResearchTitle: Temporal nitrous oxide emissions from beef cattle feedlot manure following a simulated rainfall event
|Casey, Kenneth - Texas Agrilife Research|
|Todd, Richard - Rick|
|Willis, William - Will|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2017
Publication Date: 7/13/2017
Citation: Parker, D.B., Waldrip, H., Casey, K.D., Todd, R.W., Willis, W.M., Webb, K. 2017. Temporal nitrous oxide emissions from beef cattle feedlot manure following a simulated rainfall event. Journal of Environmental Quality. 46:733-740 doi:10.2134/jeq2017.02.0042.
Interpretive Summary: Rainfall amount linearly increases nitrous oxide emissions from open-lot beef cattle feedlots. Nitrous oxide is a greenhouse gas emitted from livestock manure. Nitrous oxide has been linked to climate change, but little is known about how environmental variables such as rainfall affect nitrous oxide emissions from cattle manure. Scientists from USDA-ARS (Bushland, Texas) and Texas A&M AgriLife Research (Amarillo, Texas) studied how rainfall affects nitrous oxide emissions from beef cattle feedlot manure. Nitrous oxide emissions were monitored after applying rainfall to dry manure at five different rainfall amounts between 0 and 2 inches. There were two nitrous oxide emission peaks observed following rainfall. The first peak occurred two hours after rainfall, and the second peak occurred 15 days later. Nitrous oxide emissions were elevated for 45 days after rainfall. There was a linear relationship between rainfall and nitrous oxide emissions. Best management practices such as keeping feedlot pens dry will help to reduce nitrous oxide emissions from livestock manure.
Technical Abstract: A pilot-scale, recirculating-flow-through, non-steady-state (RFT-NSS) chamber system was designed for quantifying nitrous oxide (N2O) emissions from simulated open-lot beef cattle feedlot pens. The system employed five 1 square meter steel pans. A lid was placed systematically on each pan and headspace air was recirculated between the chamber and a real time N2O analyzer measuring concentrations every 1 s. Data was collected over 60 s sampling periods, which enabled flux in each of the five chambers to be quantified as often as every 10 min. Air-dried manure (87% dry matter) from a typical commercial feedlot in the Texas Panhandle was placed in the chambers and then 0, 6.3, 12.7, 25.4, or 50.8 mm of water was applied to simulate a one-time rainfall event. Emissions of N2O were monitored for 45 d, where two distinct flushes of N2O production were observed over time. The maximum flux (1.5 to 315 mg/(m2 h)) of the first N2O flush occurred 2 h after rainfall, with a duration of 10 h. The maximum flux (0.1 to 55 mg/m2 h)) of the second N2O flush occurred 15 d after rainfall, with a duration of 40 d. The second flush accounted for 69 to 91% of the total N2O emitted over the 45 d incubation. The mass of N2O emitted was positively related to rainfall application rate (R2 = 0.99, P < 0.001). Each mm of rainfall increased total N2O production by 263.7 mg/m2. This rainfall vs. flux relationship will be useful for modeling annual N2O emissions from open-lot beef cattle feedlots as a function of rainfall, and for assessing the effectiveness of best management practices for reducing feedlot greenhouse gas emissions.