MEASUREMENT OF NITROUS-OXIDE EMISSION FROM FERTILIZED GRASSLAND USINGMICROMETEOROLOGICAL TECHNIQUES

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