Abstract
Abstract. 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.
Highlights
As the largest corn producer in the world, the United States produces about one-third of the world’s corn crop
The objectives of this study were to evaluate the performance of the new N2O spectrometer in the eddy covariance (EC) system, to measure the N2O flux with the system, and to examine relationships between the N2O flux and soil temperature, soil moisture, precipitation, and fertilization events
For the entire experimental period, the N2O flux was positively correlated to soil moisture with a Pearson correlation coefficient r of 0.42 (p
Summary
As the largest corn producer in the world, the United States produces about one-third of the world’s corn crop (about 84 million ha in 2011) (http://www.epa.gov/agriculture/ag101/ cropmajor.html). A large proportion of applied N can leach into groundwater (e.g., NO−3 ) and/or be emitted into the atmosphere (e.g., nitrous oxide, N2O; nitric dioxide, NO; or nitrogen dioxide, NO2). The volume concentration of N2O in the atmosphere has increased from 273 parts per billion dry air mole fraction (ppbv) in 1950 to 319 ppbv in 2005 (Forster et al, 2007). N2O emitted from soil is produced by bacterial processes, mainly through nitrification and denitrification (Davidson and Swank 1986). These processes may be affected by several factors, including the percentage of water-filled pore spaces in soil (WFPS)
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