Soil Nitrous Oxide Emissions Following Deposition of Dairy Cow Excreta in Eastern Canada.
Rochette, P., Chantigny, M.H., Ziadi, N., Angers, D.A., Bélanger, G., Charbonneau, É., Pellerin, D., Liang, C., and Bertrand, N. (2014). "Soil Nitrous Oxide Emissions Following Deposition of Dairy Cow Excreta in Eastern Canada.", Journal of Environmental Quality, 43(3), pp. 829-841. doi : 10.2134/jeq2013.11.0474 Access to full text
Urine and dung deposited by grazing dairy cows are a major source of nitrous oxide (N2O), a potent greenhouse gas that contributes to stratospheric ozone depletion. In this study, we quantified the emissions of N2O after deposition of dairy cow excreta onto two grassland sites with contrasting soil types in eastern Canada. Our objectives were to determine the impact of excreta type, urine-N rate, time of the year, and soil type on annual N2O emissions. Emissions were monitored on sandy loam and clay soils after spring, summer, and fall urine (5 and 10 g N patch−1) and dung (1.75 kg fresh weight dung−1) applications to perennial grasses in two successive years. The mean N2O emission factor (EF) for urine was 1.09% of applied N in the clay soil and 0.31% in the sandy loam soil, estimates much smaller than the default Intergovernmental Panel on Climate Change (IPCC) default value for total excreta N (2%). Despite variations in urine composition and in climatic conditions, these soil-specific EFs were similar for the two urine-N application rates. The time of the year when urine was applied had no impact on emissions from the sandy loam soil, but greater EFs were observed after summer (1.59%) than spring (1.14%) and fall (0.55%) applications in the clay soil. Dung deposition impact on N2O emission was smaller than that of urine, with a mean EF of 0.15% in the sandy loam soil and 0.08% in the clay soil. Our results suggest (i) that the IPCC default EF overestimates N2O emissions from grazing cattle excreta in eastern Canada by a factor of 4.3 and (ii) that a region-specific inventory methodology should account for soil type and should use specific EFs for urine and dung.
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