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The contribution of ammonification to N2O emissions from soils - AC0105

A BBSRC Government Partnership Award. Defra funding is joint between CSA and Sustainable Farming and Food Science Division

N2O is produced during nitrate ammonification, but the contribution of this process to emissions from soils is unknown and denitrification is wrongly often presented as the only soil bacterial nitrate reduction pathway that can produce N2O. thus little is known about the environmental conditions conducive to this process, the microorganisms responsible or its significance in N2O emissions from soils. This will be addressed in an integrative research programme combining enzymological analysis of N2O production (purified NrfA and in vivo in intact cells), with physiological and molecular techniques to characterise active ammonifier communities in soils (gene expression, real time PCR) and stable isotope (15N, 18O, natural abundance, enrichment and isotopomer) techniques to determine N2O (and N2) production during ammonification. This will provide invaluable information for finding conditions conducive to the mitigation of N2O production during ammonification, which are likely to differ from those for denitrification and which are important due to the high global warming potential of this gas and its involvement in the destruction of stratospheric ozone.
1. To establish rates of N2O production from purified NrfA under a range of physiochemical conditions and in doing so evolve models for the mechanistic basis for this production.

2. To determine the effects of environmental parameters such as pH, oxygen tension and nutrient status on N2O production in continuous cultures of model ammonifiers and representative strains from soils.

3. To determine the isotopic and isotopomer signatures of N2O from different enzymatic sources in denitrification and ammonification.

4. To determine ammonification rates and N2O and N2 emitted from this process in soils of different pH (4.5-8.5), water contents/ aeration (40-80% WFPS) and different N application rates (0-25g N m-2) using stable isotope techniques (enrichment, natural abundance and isotopomers of N20).

5. To relate ammonification rates (obj. 1, 2 and 4) to the structure of microbial communities expressing nrfA (ammonicication) and nirK (denitrification) functional genes by analysis of mRNA.
Time-Scale and Cost
From: 2006

To: 2009

Cost: £55,344
Contractor / Funded Organisations
BBSRC Central Office
Climate and Weather              
Climate Change              
Environmental Protection              
Sustainable Production              
Fields of Study
Agriculture and Climate Change