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Nitrous oxide fluxes from corn fields: on-farm assessment of the amount and timing of nitrogen fertilizer
- MA, B.L., WU, T.Y., TREMBLAY, N., DEEN, W., MORRISON, M.J., MCLAUGHLIN, N.B., GREGORICH, E.G., STEWART, G.
- Global change biology 2010 v.16 no.1 pp. 156-170
- Zea mays, application methods, application timing, corn, fertilizer rates, field experimentation, greenhouse gas emissions, mineral soils, monitoring, nitrogen fertilizers, nitrous oxide, rain, soil temperature, Ontario, Quebec
- Nitrogen fertilization is considered as an important source of atmospheric N₂O emission. A seven site-year on-farm field experiment was conducted at Ottawa and Guelph, ON and Saint-Valentin, QC, Canada to characterize the affect of the amount and timing of N fertilizer on N₂O emission in corn (Zea mays L.) production. Using the static chamber method, gas samples were collected for 28-days after preplant and 28-days after sidedress fertilization at the seven site-year, resulting in 14 monitoring periods. For both methods of fertilization, peak N₂O flux and cumulative emission increased with the amount of N applied, with rates ranging from 30 to 900 μg N m⁻² h⁻¹. Depending on N amount and time of application, cumulative emission varied from 0.05 to 2.42 kg N ha⁻¹, equivalent to 0.03% to 1.45% of the N fertilizer applied. Differences in N₂O emission peaks among fertilizer treatments were clearly separated in 13 out of 14 monitoring periods. Total N₂O emissions may have been underestimated compared with annual monitoring in 10 out of the 49 cases because the monitoring period ended before N₂O efflux returned to the baseline level. The flux of N₂O was negligible when soil mineral N in the 0-15 cm layer was < 20 mg N kg⁻¹. While rainfall stimulated emission, soil temperature > 15 °C was likely the driving force responsible for the higher levels of N₂O found for sidedress than preplant application methods. However, caution must be taken when interpreting these later results as preplant fertilization may have continuously stimulated N₂O emissions after the 28-days monitoring period, especially in situations where N₂O effluxes have not fallen back to their baseline levels. Increasing fertilizer rates from 90 to 150 kg N ha⁻¹ resulted in slight increases in yields, but doubled cumulative N₂O emissions.