PRS Publications

Pastures under dry climate can be cold spots for soil nitrous oxide emissions from grazing cattle excreta

Lemke, R. L.,. 2023.


Animal excreta is an important contributor to agricultural nitrous oxide (N2O) emissions - a potent greenhouse gas. Soil N2O emissions are episodic in nature and commonly subjected to large inter-annual and spatial variation. Thus, edaphic-climatic specific studies are needed to further our knowledge on global terrestrial N2O losses and to more accurately estimate national N2O emissions. For the Canadian Prairies, multi-year studies are needed for the determination of beef cattle dung and urine derived N2O emissions under semiarid and sub-humid climate and different soil types, a knowledge gap explored by the present study. We evaluated N2O emissions in dung, urine, and unfertilized control plots following six animal excreta applications in 2009/10 and 2010/11. The experiment was conducted in two locations: (i) Swift Current, Saskatchewan (semiarid prairies/brown Chernozem); and, ii) Lacombe, Alberta (sub-humid prairies/black Chernozem). Our results indicated that beef cattle dung-N derived N2O emission was negligible for all excreta applications on both sites as cumulative N2O emissions were not significantly different from the control plots (p > 0.05). Overall, cattle urine derived soil N2O emission was greater than emissions from dung and control plots, and subjected to large inter-annual variation. For the Swift Current site, 2010 experienced record-high precipitation that stimulated N2O emissions of up to 0.47% of the applied urine-N. Except for the applications exposed to record-high precipitation, the percentage of the urine-N lost as N2O at the Swift Current site was small, ranging from 0.00% to 0.01%. Similarly, for the Lacombe site, urine-N derived N2O emissions ranged from 0.00% to 0.12%, always lower than the 0.32% default IPCC (2019) emission factor used for cattle urine-N. Our results suggest that dry climate locations under near-normal or below-normal precipitation levels are natural "cold spots" for N2O emissions and could experience negligible cattle excreta derived soil N2O emissions.