mw. N. Wrage : Pitfalls in measuring nitrous oxide production by nitrifiers


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28 Feb 2003 16:00

Unit: Wageningen University

Location: Aula (gebouw 362), Gen. Foulkesweg 1, Wageningen

Website: http://www.wau.nl/pers/03/009.html

Promotor: prof.dr. O. Oenema (Management of Nutrient Fluxes and Soil Fertility)prof.dr. H.J. Laanbroek (NIOO, Nieuwersluis, the Netherlands)

Co Promotor: dr.ir. G.L. Velthof (Alterra)

Fertilized soils can emit large amounts of nitrous oxide (N2O), a greenhouse gas that causes presently 6% of global warming. To mitigate N2O production, information about all producing pathways and influencing factors is needed. In soils, N2O is mainly produced by nitrifiers and denitrifiers. Nitrifiers produce N2O in nitrification as a by-product of ammonia oxidation and in nitrifier denitrification as an intermediate in a barely explored pathway presumably similar to denitrification. To differentiate between N2O sources in soils, incubations with small concentrations of acetylene (C2H2, 0.02 kPa) and large concentrations of oxygen (O2, 100 kPa) are usually done. In this thesis, we show that this method is not suitable. Small concentrations of C2H2 did not inhibit N2O production by Nitrosospira briensis, an important nitrifier. Large concentrations of O2 did not specifically inhibit the target pathways, but also influenced other pathways of N2O production. Due to these methodological problems, nitrifiers have so far probably been underestimated as producers of N2O. Furthermore, indications of a potentially unknown pathway of N2O production in nitrifiers have been found. This needs further investigation. See also: http://www.dow.wau.nl/soil_quality/nieuw/org/people/wragen.htm

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