Nitrous oxide production and nitrification in acidic soil from a dutch coniferous forest

Abstract

The production of nitrous oxide and nitrification were studied using aerobic incubations of soil sampled from the F-layer of a nitrogen-saturated Douglas fir stand (The Netherlands). The nitrous oxide production (3 ng N 2O-N g −1 dry soil h −1) in the acid soil (pH 3.7) could be inhibited by 90% using low (3 Pa) or high (2.5 kPa) acetylene concentrations. The experiments with aerobic soil slurries showed that N;0 production at pH 4 was 4–8 times higher than at pH 6. Also the nitrification rate was higher at pH 4 than at pH 6. The ratio of N 2O-N to NO 3 −-N was higher at pH 4 (0.33–0.47%) than at pH 6 (0.04–0.18%). Acetylene (2.5 kPa) or nitrapyrin (10μgml −1) inhibited N 2O (40–96%) and NO 3 − production (79–100%) in the soil slurries indicating the importance of chemolithotrophic bacteria. The results showed that N 2O is produced in a nitrogen-saturated acid forest soil in North Western Europe even if well-aerated. The aggregated ammonium oxidizers ( Nitrosospira) that are responsible for ammonium oxidation in these acid soils may have importance in N 2O production. The possible significance of the aggregation of Nitrosospira cells for N 2O production is discussed.