Seasonal Distribution of Nitrous Oxide Emissions from Soils in the Parkland Region
1998
Lemke, R. L. | Izaurralde, R. C. | Nyborg, M.
The temporal variability of soil-derived N₂O emissions presents a major challenge to the accurate quantification of N₂O-N losses from agroecosystems. We characterized the seasonal distribution of N₂O emissions from two agricultural sites in the Parkland region of Alberta during 1993 and 1994. Treatments studied were fallow, and spring wheat (Triticum aestivum L.) with and without urea fertilizer, under conventional till management. Gas samples were collected from vented static soil chambers and were analyzed for N₂O with a gas chromatograph equipped with a ⁶³Ni electron capture detector. Soil water content and concentrations of NO⁻₃-N, NH⁺₄-N, and water-soluble organic C (WSOC) were measured several times during the season. A brief burst of N₂O emission was recorded at both sites during and immediately following spring snow melt. A second period of activity occurred between mid-June and mid-July. Between 16 and 60% of estimated annual N₂O-N loss occurred during spring thaw, while >80% of cumulative annual N₂O-N loss had occurred by mid-July. Mean soil NO⁻₃-N concentration explained up to 65% of the temporal variability in geometric mean N₂O emissions. A multiple regression model that included fall soil concentrations of NO⁻₃-N, NH⁺₄-N, and WSOC explained 94% of the variability in estimated cumulative N₂O-N loss during the following spring thaw. Most N₂O-N losses in the Parkland region appear to occur during spring thaw and early summer; therefore, sampling schedules need to focus on these time periods. Management practices that minimize N availability during spring thaw may be an effective mitigation strategy for this region.
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