Nitrous oxide (N₂O) fluxes associated with the long-term manure and fertilizer application plots at Humboldt, SK were measured over a two year period from 2009 to 2010. Plots received either liquid swine manure (LSM), solid cattle manure (SCM), or banded urea. Gas fluxes were measured more frequently (1–2 times per week) at the start of the season (i.e., during spring thaw and following seeding) and less frequently (once every 2–3 weeks) at the end of the season. Gas fluxes also were measured 24–48 hours after any significant precipitation event during the sampling season. In addition, denitrification enzyme activity (DEA) was measured in spring, mid-summer and early fall.
Daily N₂O fluxes were highly variable, but followed the general event based/background pattern; DEAs were significantly greater in the plots receiving the highest manure applications. In general, it was determined that (1) emission factors for the urea- and manure-amended plots were in the range (i.e., 0.2–1.0) normally associated with prairie agriculture; (2) N₂O emissions from LSM-amended soils increase with increasing rate and intensity of the manure-N application; (3) long-term applications of manure-N can, at high application rates or following frequent manure applications, produce a ‘priming’ effect which may exacerbate N₂O emissions if a more available form of N (e.g., urea fertilizer) is applied to the soil; and (4) the variable effects of the LSM and SCM on soil N₂O emissions are a reflection of the variable compositions of the manures as well as interactions with soil environmental conditions and soil management practice.