Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

Abstract. Temperature is a primary factor affecting greenhouse gas (GHG) emissions from agricultural soils, but little is known about how temperature affects nitrous oxide (N₂O) emissions from manure. The majority of grain-fed cattle in the Texas Panhandle are finished in large, earthen-surfaced, open-lot feedyards. Manure accumulates in feedyard pens and creates an environment high in nitrogen (N) and carbon (C) that can lead to N₂O losses. In previous studies, N₂O-N emissions from feedyard manure have been highly variable, ranging from negligible amounts from dry manure to 200 mg m^-2 h^-1 after a simulated rainfall event. The objective of this research was to determine how temperature affects N₂O emissions from feedyard manure following rainfall. A recirculating flow-through, non-steady-state (RFT-NSS) chamber system with 1 m² pans was used to monitor N₂O emissions from beef cattle manure following a single 25.4 mm simulated rainfall event. Emissions were monitored at manure temperatures of 5.0°C, 11.2°C, 17.2°C, 21.5°C, 26.8°C, 31.0°C, 38.1°C, and 46.2°C. At all temperatures, a single N₂O episode was observed following rainfall, peaking 2 to 11 h after rainfall with duration of 2 to 3 d. A second N₂O episode was observed at temperatures ≥31.0°C, peaking 3 to 4 d after rainfall with duration of 18 d. When present, the second N₂O episode accounted for 72% to 83% of the 20 d cumulative emissions. A step-increase in cumulative N₂O emissions was observed between 26.8°C and 31.0°C, believed to be due to a major shift from denitrification to nitrification as the primary process of N₂O production. Empirical regression models were developed for predicting cumulative N₂O emissions based on temperature, which showed 88% agreement between predicted and field-observed N₂O-N flux rates. These regression models will be useful for further quantification of N₂O emissions from open-lot beef cattle feedyards in the U.S. Southern High Plains and for assessment of practices for reducing GHG emissions.