LABORATORY STUDY OF THE EMISSION OF NO AND N2O FROM SOME BELGIAN SOILS

The NO, NO2 and N2O emission was measured, upon application of nitrate , ammonium and both, to four Belgian soils with different characterist ics. The addition of NH4+ caused higher NO and N2O emissions than the addition of no nitrogen, or the addition of NO3-. In contrast to the t wo soils with a pH of approximately 8 the two soils with a pH around 6 showed a considerable delay in production of both NO and N2O upon the application of the ammonium, probably due to the lag-period of nitrif ication. The soils with a pH of 8 gave higher emissions on the applica tion of NH4+ than the soils with a pH of 6. The emission of NO2 was fo und to be considerably lower than the NO emission from the soils. The NO/NO2 ratio varied between 5-25 at considerable NO emissions (>50 nmo l kg-1). In the controls of soil 1 and soil 2, which showed very low N O emissions ratios of < 1 were observed. The N2O/NO ratios varied betw een 5-20 when NO emissions were considerable (>50 nmol kg-1). Soil 3 a nd 4 gave lower N2O/NO ratios than soil 1 and 2. In the controls of so il 1 and soil 2, at low NO emissions, N2O/NO ratios of > 300 were obse rved. Soil 3 and 4 gave higher NO/NO2 and lower N2O/NO ratios than soi l 1 and 2.