Fluxes of oxidized nitrogen gases from fertilized agricultural fields

This thesis is an investigation of fluxes of oxidized N gases (N ₂O, NO and NO₂) as affected by: (1) N fertilizer type applied during growing seasons, and as affected by winter and spring-thaw conditions after fall fertilization; (2) two application methods of liquid manure and mineral fertilizer; (3) the use different calculation approaches for the integrated eddy diffusivity in the flux gradient method and different sampling frequencies.; During the three growing seasons studied, urea-based fertilizers seemed to minimize N₂O emissions, and ammonium nitrate (AN) presented very high emissions when rainfall occurred after the fertilizer application. Slow-release urea (SRU) form initially reduced emissions but increased N ₂O fluxes in the long-term. The urea (U) plot had significantly higher NO emissions and NO₂ uptake during all seasons compared to other fertilized plots. Turfgrass acted as a sink for NO_x, since NO _x uptake occurred at higher rates than NO emission.; During the winter/spring-thaw experiment, N₂O emissions were small during winter, increasing significantly in March. The highest loss of N₂O-N was from the SRU plot. The NO fluxes from U and AN fertilized plots were statistically higher than for other plots. NO₂ fluxes were similar for all plots and indicated constant deposition, which decreased when there was snow.; The effect of two liquid manure application methods (surface applied, SLM; incorporated, ILM) on gaseous emissions from a barley field indicated that during the spring, the incorporation decreased N₂O and NO _x fluxes. The moisture at the depth of incorporation may have influenced N₂O emissions. Statistically higher N₂O and NO emissions were measured from the ILM in comparison to other treatments during the fall.; The study of different approaches of eddy diffusivity calculation indicated that using wind profile data and an estimated sensible heat flux resulted in a higher number of measurements in comparison to the sonic approach, which is desired in a continuous measurement scheme. The total N₂O losses using each calculation approach were not statistically different. The sampling rate simulation showed that the determination of the sampling interval for a non-continuous measurement scheme should account for soil and environmental conditions, since a fixed interval could miss important N₂O emission events.