Nitrous Oxide and Ammonia Emissions from Biodigested Dairy Slurry.
Elizabeth Pattey1, Anna Crolla2, Dave Dow1, Raymond Desjardins1, and Christopher Kinsley2. (1) Research Branch, Agriculture and Agri-Food Canada, 960 Carling Ave. KW Neatby Bldg., Ottawa, ON K1A 0C6, Canada, (2) Ontario Rural Wastewater Centre, University of Guelph, Alfred, ON K0B 1A0, Canada
Anaerobic digestion of manure offers the potential benefit of reducing greenhouse gas emissions. As part of the complete life cycle analysis of this technology, nitrous oxide and ammonia emissions following field application of raw and biodigested dairy slurry were measured in a dairy cow production area of Eastern Canada. The experiment was carried out at an experimental farm near Ottawa (ON) in a 24-ha clay loam field after the harvest of spring wheat in the fall of 2005. The biodigested dairy slurry was applied in the middle section of the field, which was subdivided in three sections of 400m x 200m each, while non-biodigested slurry was applied on the end sections. Two micrometeorological towers were set up on the section boundaries to measure energy and trace gas fluxes almost continuously for various wind directions. Each eddy covariance tower was equipped with a 3-D sonic anemometer and a fast-response infrared CO2-H2O analyzer. Two Tunable Diode Lasers were used to measure N2O and NH3 gradients at 1.5 m and 2.5 m above the displacement height sequentially every half-hour at section boundaries. NH3 fluxes were also measured by the relaxed eddy accumulation technique using oxalic acid denuder tubes. Background N2O emissions were measured for 18 days prior to the application of dairy slurry in the field. The dairy slurry application lasted 3 days and the N rate was about 80 kg N ha-1. The digested manure contained more ammonium than the raw slurry. The fall N2O emissions were low for both slurry applications, while higher ammonia emissions were measured from the biodigested slurry. During the 2006 snowmelt, total N2O fluxes for the raw manure was 1.5kg N ha-1 and 2.4kg N ha-1 for digested manure. The application of biodigested slurry enhanced the N2O emission over the two main emission periods by almost 70%.