Measurements of nitrous oxide emission from fertilised grassland using micrometeorological techniques.

Fluxes of N2O from a recently fertilized grassland growing on a heavy clay soil were determined using flux gradient micrometeorological techniques. Three separate techniques were employed (gas chromatograph, Fourier transform infrared spectroscopy and tunable diode laser spectroscopy) to measure small gradients in N2O concentration close to the surface. After application of 185 kg NH4NO3 ha−1 to the site, emission fluxes in the range 0 to 100 ng N2O-N m−2 s−1 (0 to 86 g N2O-N ha−1 day−1) were measured from an ungrazed part of the field. Agreement between the three independent techniques was good, thus establishing the suitability of micrometeorological methods for making measurements of N2O emission at the field scale, integrating the great spatial variability in N2O emission rates which is frequently observed using box enclosures