Nitrous oxide production in grassland soils: assessing the contribution of nitrifier denitrification
2004
Wrage, N. | Velthof, G.L. | Laanbroek, H.J. | Oenema, O.
Nitrifier denitrification is the reduction of NO2 - to N2 by nitrifiers. It leads to the production of the greenhouse gas nitrous oxide (N2O) as an intermediate and possible end product. It is not known how important nitrifier denitrification is for the production of N2O in soils. We explored N2O production by nitrifier denitrification in relation to other N2O producing processes such as nitrification and denitrification under different soil conditions. The influence of aeration of the soil, different N sources, and pH were tested in four experiments. To differentiate between sources of N2O, an incubation method with inhibitors was used [Biol. Fertil. Soils 22 (1996) 331]. Sets of four incubations included controls without addition of inhibitors, incubations with addition of small concentrations of C2H2 (0.01-0.1 kPa), large concentrations of O2 (100 kPa), or a combination of C2H2 and O2. The results indicate that the availability of NO2- stimulated the apparent N2O production by nitrifier denitrification. A decreasing O2 content increased the total N2O production, but decreased N2O production by nitrifier denitrification. No significant effect of pH could be found. The study revealed problems concerning the use of the inhibitors C2H2 and O2. Almost one-third of all incubations with inhibitors produced more N2O than the controls. Possible reasons for the problems are discussed. The inhibitors C2H2 and O2 need to be tested thoroughly for their effects on different N2O producing processes before further application.
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