EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Quantifying nitrous oxide emissions in space and time using static chambers and eddy covariance from a temperate grassland

Rachael Murphy1,2, Karl Richards1, Dominika Krol1, Amanuel Gebremichael1, Luis Lopez-Sangil1, James Rambaud1, Nicholas Cowan3, Gary Lanigan1, and Matt Saunders2
Rachael Murphy et al.
  • 1Teagasc Research Johnstown Castle, Soils and Environment, Wexford, Ireland (
  • 2Department of Botany, Trinity College Dublin, Dublin 2, Ireland (
  • 3UK Centre for Ecology and Hydrology, Bush Estate, Penicuik, Midlothian, UK (

Nitrous oxide (N2O) is a potent greenhouse gas (GHG), with a global warming potential (GWP) of 265 relative to carbon dioxide (CO2) and a lifespan of over 100 years. Where N input from fertilizers exceeds plant demands, hotspots of N2O can be produced releasing short-lived pulses of N2O from the soil that exhibit disproportionately high rates of emissions relative to longer periods of time, known as hot moments. Hotspots and hot moments of N2O are sensitive to changes in agricultural management and the environment making it difficult to accurately quantify N2O emissions with low uncertainties. This study investigates the methods used to quantify N2O emissions in time and space, using both static chambers (SC) and eddy covariance (EC) techniques.N2O fluxes were measured from both techniques from an intensively managed grassland site under four fertilizer applications of calcium ammonium nitrate (CAN) in 2019. EC measurements of N2O were gap-filled by using a simple linear empirical model that incorporated environmental and management data. SC N2O fluxes were calculated using the arithmetic method and Bayesian statistics via Markov Chain Monte-Carlo (MCMC) simulations to account for the log-normal distribution of fluxes measured. N2O emissions were weakest in winter for both techniques (-3.27 µg N2O-N m-2 hr-1 for SC and -3.9 µg N2O-N m-2 hr-1 for EC). Following fertilizer application, daily averaged N2O emissions peaked in March (538.89 µg m-2 hr-1 for SC, 491.18 µg m-2 hr-1 for EC) and April (117.91 µg m-2 hr-1for SC and 306.90 µg m-2 hr-1 for EC). Delayed peaks in N2O emissions following fertilizer application occurred in June (101.03 µg m-2 hr-1 for SC and 814.76 µg m-2 hr-1 for EC) and October (417.14 µg m-2 hr-1 for SC and 313.22 µg m-2 hr-1 for EC) and these high emissions events coincided with dry periods followed by rainfall events. EC and SC measurements were most comparable when emissions were > 115 µg m-2 hr-1, when the flux footprint of half-hourly EC flux measurements overlapped with the position and time of SC measurements and when the number of chamber replicates were ≥ 15 on a given sampling day. Where the chamber sample size was small (n ≤ 5), the Bayesian method produced large uncertainties (> 25,000 µg m-2 hr-1) due to the inability to constrain an arithmetic mean from a log-normally distributed data set. Annual cumulative N2O fluxes from EC and SC by the arithmetic and Bayesian method, were 3.35(± 0.5) kg N ha-1, 2.98 (± 0.17) kg N ha-1and 3.13 (± 0.24) kg N ha-1 respectively. Emission factors from EC and SC by the arithmetic and Bayesian method were higher than the Intergovernmental Panel on Climate Change (IPCC) default value of 1%, at 1.46%, 1.30% and 1.36%, respectively. Our study highlights that disparities exist between SC and EC in quantifying N2O fluxes from a managed grassland and we recommend constraining disparities by utilizing a SC sample size > 5 and by accounting for the log-normal distribution of N2O flux data to accurately estimate N2O flux uncertainty.

How to cite: Murphy, R., Richards, K., Krol, D., Gebremichael, A., Lopez-Sangil, L., Rambaud, J., Cowan, N., Lanigan, G., and Saunders, M.: Quantifying nitrous oxide emissions in space and time using static chambers and eddy covariance from a temperate grassland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-515,, 2021.