Measurement of nitrous oxide emission from agricultural land using micrometeorological methods

Hargreaves, K J and Wienhold, F G and Klemedtsson, L and Arah, J R M and Beverland, I J and Fowler, D and Galle, B and Griffith, D W T and Skiba, U and Smith, K A and Welling, M and Harris, G W (1996) Measurement of nitrous oxide emission from agricultural land using micrometeorological methods. Atmospheric Environment, 30 (10-11). pp. 1563-1571. ISSN 1352-2310

Abstract

The spatial variability of N2O emission from soil makes extrapolation to the field scale very difficult using conventional chamber techniques (<1 m(2)). Micrometeorological techniques, which integrate N2O fluxes over areas of 0.1 to 1 km(2) were therefore developed and compared with chamber methods over arable cropland. Measurements of N2O emission from an unfertilised organic soil (reclaimed from the sea in 1879) were made over a 10 d period at Lammefjord, Denmark. Flux-gradient and conditional sampling techniques were applied using two tunable diode laser spectrometers (TDLs), a Fourier transform infra-red spectrometer (FTIR) and a gas chromatograph (GC). Eddy covariance measurements were also made by the TDLs. Over the 10 d campaign approximately 5 d of continuous fluxes by the different methods were obtained. Fluxes determined by eddy covariance were in reasonable agreement, showing a mean flux of 269 mu g N m(2) h(-1). Flux-gradient techniques measured a mean flux of 226 mu g N m(-2) h(-1). The mean flux measured by conditional sampling was 379 mu g N m(-2) h(-1). The maximum annual emission of N2O from this soil system was estimated to be 23.5 kg N ha(-1).

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