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 characteristics. The addition of NH 4 (+) caused higher NO and N2O emissions than the addition of no nitrogen, or the addition of NO 3 (-) . In contrast to the two 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 nitrification. The soils with a pH of 8 gave higher emissions on the application of NH 4 (+) than the soils with a pH of 6. The emission of NO2 was found to be considerably lower than the NO emission from the soils. The NO/NO2 ratio varied between 5-25 at considerable NO emissions (>50 nmol kg(-1)). In the controls of soil 1 and soil 2, which showed very low NO emissions ratios of <1 were observed. The N2O/NO ratios varied between 5-20 when NO emissions were considerable (>50 nmol kg(-1)). Soil 3 and 4 gave lower N2O/NO ratios than soil 1 and 2. In the controls of soil 1 and soil 2, at low NO emissions, N2O/NO ratios of >300 were observed. Soil 3 and 4 gave higher NO/NO2 and lower N2O/NO ratios than soil 1 and 2.