Atmosphere composition and N2O emissions in soils of contrasting textures fertilized with anhydrous ammonia
2004
Régis R. Simard, Philippe Rochette | Michel C. Nolin, Noura Ziadi | Cambouris, Athyna N.
Nitrous oxide production and emission in agricultural soils are often influenced by soil physical properties and mineral N content. An experiment was initiated on a commercial farm located in the St. Lawrence Lowlands to measure the effects of recommended (150 kg N ha⁻¹) and excessive (250 kg N ha⁻¹) rates of anhydrous ammonia on atmospheric composition (O₂, CO₂, CH₄ and N₂O) and N₂O emissions in soils of contrasting textures (sandy loam, clay loam and clay) cropped to corn. N₂O emissions and soil temperature, water content and atmospheric composition were measured from post-harvest tillage to the first snowfall during the first year (2000), and from spring thaw to mid-July during the following 2 yr. Episodes of high N₂O concentrations and surface emissions coincided with periods of high soil water content shortly following rainfall events when soil O₂ concentrations were lowest. The convergence of indicators of restricted soil aeration at the time of highest N₂O production suggested that denitrification was a major contributor to N₂O emissions even in soils receiving an NH₄-based fertilizer. Soil texture had a significant influence on soil N₂O concentration and emission rates on several sampling dates. However, the effect was relatively small and it was not consistent, likely because of complex interactions between soil physical properties and N₂O production, consumption and diffusion processes. Nitrous oxide emissions during the study were not limited by soil N availability as indicated by similar fluxes at recommended and excessive rates of anhydrous ammonia. Finally, greater N₂O emissions in 2001 than in 2002 stress the importance of multiyear studies to evaluate the effect of annual weather conditions on soil N₂O dynamics. Key words: Greenhouse gasses, denitrification
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