Location: Livestock Nutrient Management ResearchTitle: Toward modeling of nitrous oxide emissions following precipitation, urine and feces deposition on beef cattle feedyard surfaces
|CASEY, KENNETH - Texas A&M Agrilife|
|HALES, KRISTIN - Texas Tech University|
|CORTUS, ERIN - University Of Minnesota|
|Willis, William - Will|
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2020
Publication Date: 10/1/2020
Citation: Parker, D.B., Casey, K.D., Hales, K., Waldrip, H., Min, B., Cortus, E., Woodbury, B.L., Spiehs, M.J., Meyer, B.E., Willis, W.M. 2020. Toward modeling of nitrous oxide emissions following precipitation, urine and feces deposition on beef cattle feedyard surfaces. Transactions of the ASABE. 63(5):1371-1384. (doi: 10.13031/trans.13847)@2020.
Interpretive Summary: Nitrous oxide, a greenhouse gas linked to climate change, is emitted from manure at open-lot beef cattle feedyards. In earlier research, we determined that precipitation increases nitrous oxide emissions. However, little is known about how the moisture from urine and feces deposited on the feedyard pen surface affects these same emissions. Scientists from USDA-ARS (Bushland, Texas and Clay Center, Nebraska), Texas A and M AgriLife Research (Amarillo, Texas), Texas Tech University (Lubbock, Texas), and University of Minnesota (St. Paul, Minnesota) studied how urine and feces deposition affects nitrous oxide emissions from the feedyard pen surface. Nitrous oxide emissions from the moisture in urine and feces were smaller than those from precipitation, ranging from 16 percent for feces to 33 percent for urine. The emissions were still large enough to warrant including in annual emission estimates. These findings will be used in future modeling efforts to estimate annual nitrous oxide emissions from beef cattle feedyards.
Technical Abstract: The amount of moisture deposited annually as urine (320 mm) and feces (95 mm) on typical semiarid Texas beef cattle feedyard pens is considerable compared to the regional 470 mm mean annual precipitation. Precipitation is a primary factor affecting nitrous oxide (N2O) emissions from manure, but specific effects of urine and feces deposition are unknown. The objectives of this research were to 1) quantify N2O emissions following precipitation, urine, and feces deposition on a dry feedyard manure surface, and 2) develop equations for future empirical modeling of these emissions. Four experiments were conducted using recirculating flux chambers to quantify N2O emissions. Exp. 1 had treatments (TRT) of water (W), artificial urine (AU), and two urines collected from beef cattle fed high quality forage (FU) or corn-based concentrate (CU). Exp. 2 had TRT of W, AU, and two feces levels (Fx1 and Fx2). In Exp. 3, N2O emissions were quantified from fresh feces pats. In Exp. 4, the effect of rainfall pH on N2O emissions was evaluated. Results from Exp. 1 showed that the W TRT had the highest mean cumulative N2O emission, while AU, FU, and CU ranged from 31.0 to 70.0 percent of W on an equal volume-applied basis. There was little correlation between N2O emissions and urine or water nitrogen (N) content. In Exp. 2, W again had the highest cumulative N2O. Cumulative N2O emissions expressed per unit of water added were 29.0, 3.8, 4.5, and 5.1 mg N per kg water added for W, AU, Fx1, and Fx2, respectively. In Exp. 3, fresh feces pats emitted no direct N2O, but N2O originated from the dry manure beneath the feces pat due to wetting. In Exp. 4, the highest N2O emissions occurred at pH 5 and pH 8, with lower emissions at pH 6 and pH 7. This research has shown that the addition of moisture to the pen surface from urine and feces contributes considerably to N2O emissions as compared to precipitation alone. The following recommendations were developed for future empirical modeling purposes: 1) N2O emissions from urine should be calculated as 32.7 percent of those emissions from the equivalent mass deposition of water, and 2) N2O emissions resulting from the mass of water in feces should be calculated as 15.6 percent of those emissions from the equivalent mass deposition of water.