Nitrous oxide emissions from a commercial cornfield (<i>Zea mays</i>) measured using the eddy covariance technique

Abstract

Abstract. Increases in observed atmospheric concentrations of the long-lived greenhouse gas nitrous oxide (N 2 O) have been well documented. However, information on eventrelated instantaneous emissions during fertilizer applications is lacking. With the development of fast-response N 2 O analyzers, the eddy covariance (EC) technique can be used to gather instantaneous measurements of N 2 O 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 N 2 O flux with the system, and finally to examine relationships of the N 2 O flux with soil temperature, soil moisture, precipitation, and fertilization events. An EC system was assembled with a sonic anemometer and a fast-response N 2 O 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 N 2 O EC system provided reliable N 2 O flux measurements. The cumulative emitted N 2 O amount for the entire growing season was 6.87 kg N 2 O-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 N 2 O emissions in crop fields over a growing season of more than 100 days.

Standardisation of eddy-covariance flux measurements of methane and nitrous oxide

“…This estimate comes from the first available long-term flux measurement datasets from managed crops and grassland measured with this technology (e.g. Huang et al, 2014; as well as unpublished datasets obtained by the authors; Merbold et al, 2014) and is also consistent with the detection limit reported during field deployments. Based on an intercomparison study carried out during the Integrated non-CO 2 Greenhouse gas Observing System (InGOS) project, Nemitz et al (2018) reported differences in standard deviations of flux values derived in the field were about twice the value reported by the manufacturers.…”

N2O Emissions From Two Agroecosystems: High Spatial Variability and Long Pulses Observed Using Static Chambers and the Flux‐Gradient Technique

“…Figures S16-S20 illustrate how the relationships between N 2 O and CO 2 emissions break down by individual chamber and by winter and growing season time periods. The emission rates observed in this study are comparable to literature values (Huang et al, 2014; Figure S14). However, we are interested in increasing our knowledge of local N 2 O emission behavior.…”

Applicability of an eddy covariance system based on a close-path quantum cascade laser spectrometer for measuring nitrous oxide fluxes from subtropical vegetable fields

“…According to the methods introduced by Moncrieff et al (2004) and Ibrom et al (2007), the final N 2 O fluxes were corrected for this systematic underestimation by on average of 18%. The magnitude of the co-spectra correction agreed with the results reported by Huang et al (2014). The two periods we analyzed had different canopy conditions.…”

“…This piece of data was collected in the afternoon of 20 December 2014, when turbulence was well developed and N 2 O emissions were weak. Although the precision may have been even better by taking samples of standard gas, it was very close to the average estimates (0.31 ± 0.29 nmol mol −1 at 1 Hz) reported by previous studies that applied this kind of QCL analyzer (Kroon et al 2007;Neftel et al 2007Neftel et al , 2010Huang et al 2014;Rannik et al 2015).…”

“…Compared with the traditional laser spectrometer, this type of laser is more sensitive and carries a number of other advantages such as compactness, high selectivity in operating frequencies, and without using liquid-nitrogen for laser cooling. QCL instruments have been previously used for N 2 O flux measurements on managed grasslands (Kroon et al 2007;Neftel et al 2007Neftel et al , 2010Merbold et al 2014) and agricultural fields (Huang et al 2014;Rannik et al 2015). However, the performance of the laser in these studies varied due to many factors, such as the wavelength and mode of the laser adopted during operation, the field and environmental conditions, and the manner of the daily maintenance applied by the instrument users, which led to differences in the performance of the QCL-EC system.…”