STUDIES ON NO AND N2O FLUXES FROM A WHEAT FIELD

The importance of soil parameters and the other environmental conditio ns that affect emission rates of NO and N2O were studied over a fertil ised wheat field. Open-chamber and closed-chamber techniques were used for the flux measurement of NO and N2O, respectively. Both gases show ed variation in the emission rates which followed the seasonal variati on in the available HN4+ and NO3- and the moisture content of the soil . Whilst N2O emission rates increased with the moisture content of the soil, NO emissions decreased with increasing soil moisture and rainfa ll. The results suggested that most soil variables and atmospheric par ameters had similar effects on both NO and N2O emission rates but that the overriding influence upon the NO/N2O emission ratio is the soil m oisture content. The NO flux showed a clear diurnal variation which fo llowed the surface soil temperature with an activation energy of 108 k J mol(-1). The annual NO flux estimated from this study (0.79 kg N ha( -1)) was approximately half the corresponding N2O (1.42 kg N ha(-1)).