Nitrous oxide emissions from a commercial cornfield (Zea mays) measured using the eddy-covariance technique

Increases in observed atmospheric concentrations of the long-lived greenhouse gas nitrous oxide (N₂O) have been well documented. However, information on event-related instantaneous emissions during fertilizer applications is lacking. With the development of fast-response N₂O analyzers, the eddy covariance (EC) technique can be used to gather instantaneous measurements of N₂O concentrations to quantify the exchange of nitrogen between the soil and atmosphere. The objectives of this study were to evaluate the performance of a new EC system, to measure the N₂O flux with the system, and finally to examine relationships of the N₂O flux with soil temperature, soil moisture, precipitation, and fertilization events. An EC system was assembled with a sonic anemometer and a fast-response N₂O analyzer (quantum cascade laser spectrometer) and applied in a cornfield in Nolensville, Tennessee during the 2012 corn growing season (4 April-8 August). Fertilizer amounts totaling 217 kg N ha^-1 were applied to the experimental site. Results showed that this N₂O EC system provided reliable N₂O flux measurements. The cumulative emitted N₂O amount for the entire growing season was 6.87 kg N₂O-N ha^-1. Seasonal fluxes were highly dependent on soil moisture rather than soil temperature. This study was one of the few experiments that continuously measured instantaneous, high-frequency N₂O emissions in crop fields over a growing season of more than 100 days.