Nitrous Oxide and Carbon Dioxide Fluxes from a Bare Soil Using a Micrometeorological Approach

Abstract

Increasing atmospheric carbon dioxide (CO2) and nitrous oxide (N2O) levels have prompted research on management of the soil C and N pools. The impact of C and N fertilizer addition on N2O and CO2 field emissions is not clear. We determined N2O and CO2 fluxes from a 1‐ha bare soil plot using micrometeorological methods with the objective of evaluating the effect of management practices (cultivation, irrigation, fertilizer, and sucrose applications) on the relative importance of both trace gases. Research was conducted at the Elora Research Station (Typic Hapludalf) in Ontario, Canada, over 7 mo. The N2O concentration gradients were measured using a Tunable Diode Laser Trace Gas Analyzer and the CO2 gradients using an Infra‐Red Gas Analyzer. The transport coefficients were calculated using a Bowen Ratio Energy Balance and two wind profile approaches. These three approaches resulted in similar hourly fluxes. Daily N2O fluxes for nonevent periods were 12 ng m−2 s−1 in 1991, and 2 ng m−2 s−1 in the summer of 1992, while CO2 fluxes before treatments in 1991 were 0.18 mg m−2 s−1. Sucrose addition (420 kg C ha−1) resulted in the highest N2O and CO2 daily emissions measured during the experiment at 3100 ng m−2 s−1 and 0.5 mg m−2 s−1, respectively. Peak emissions of 250 ng N2O m−2 s−1 were measured after wetting of dry soil (WFP < 0.4) through irrigation in 1991, and rain in 1992. Application of ammonium sulfate (100 kg N ha−1) and irrigation increased N2O emissions to 75 ng m−2 s−1, with a smaller effect caused by two subsequent irrigations on wet soil (WFP > 0.6). Carbon dioxide fluxes varied between 0.01 and 0.5 mg m−2 s−1 being the predominant gas contributing to an equivalent CO2 global‐warming potential, but addition of sucrose increased the contribution of N2O to twice the contribution of CO2. The combined effect of C and N additions (e.g. manure and legume) on the N2O emissions in irrigated or high rainfall areas should be considered in the efforts of atmospheric C sequestering.

Towards standards for measuring greenhouse gas fluxes from agricultural fields using instrumented towers

“…In these cases multiple towers and the use of small plots can be an effective experimental design for questions relating to the application of differing treatments. A novel small plot (e.g., 1 ha) method based on the TGA100 measuring system with multiple pairs of gradient intakes was developed at the University of Guelph and has been successfully applied (Wagner-Riddle et al 1996aWagner-Riddle and Thurtull 1998) to study the relative impact of various treatments on N 2 O emission to the atmosphere. The experimental design involves location of the instrument trailer in the centre of four 1-ha fields (Fig.…”

Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods

“…Counter-gradient transport of heat, momentum, and trace gases has been documented beneath plant canopies and may severely compromise fluxgradient methods (Shaw, 1977;Raupach and Thom, 1981;Amiro 1990;Baldocchi and Meyers, 1991). On the other hand, flux-gradient methods have been preferred over eddy covariance techniques for measuring surface-atmosphere fluxes within a few meters of the surface layer (Fitzjarrald and Lenschow, 1983;Gao et al, 1991;de Arellano and Duynkerke, 1992;Wagner-Riddle et al, 1996;Taylor et al, 1999;Dunn et al, 2009). Intermittent turbulent transport events may become less important near the ground, where the sources or sinks of tracers can be large; therefore, Meyer et al (1996) argue that the flux-gradient relationships near the forest floor are valid and their application is justified.…”

Wavelet analysis of wintertime and spring thaw CO2 and N2O fluxes from agricultural fields

“…Isolated missing data points in the daily flux time series were linearly filled in using adjacent data points. Data were filtered to exclude times of low turbulence and times of instrument malfunction (Wagner-Riddle et al, 1996.…”