BGD Biogeosciences Discussions BGD 1810-6285 Copernicus GmbH Göttingen, Germany 10.5194/bgd-8-3253-2011 The effect of aggregates on N<sub>2</sub>O emission from denitrification in an agricultural peat soil Stolk P. C. 1 Hendriks R. F. A. 2 Jacobs C. M. J. 1 Moors E. J. 1 Kabat P. 1 Earth System Science and Climate Change Group, Wageningen University and Research Centre, Wageningen, The Netherlands Integrated Water Management, Alterra, Wageningen University and Research Centre, The Netherlands 23 03 2011 8 2 3253 3287 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.biogeosciences-discuss.net/8/3253/2011/bgd-8-3253-2011.html The full text article is available as a PDF file from http://www.biogeosciences-discuss.net/8/3253/2011/bgd-8-3253-2011.pdf

Nitrous oxide (N<sub>2</sub>O) emissions are highly variable in time, with high peak emissions lasting as couple of days to weeks and low background emissions. This temporal variability is poorly understood which hampers the simulation of daily N<sub>2</sub>O emissions. In structured soils, like clay and peat, aggregates hamper the diffusion of oxygen, which leads to anaerobic microsites in the soil, favourable for denitrification. In this paper we studied the effect of aggregates in soils on the N<sub>2</sub>O emissions from denitrification. We presented a parameterization to simulate the effects of aggregates on N<sub>2</sub>O, following the mobile-immobile model concept. This parameterization was implemented in a field-scale hydrological-biogeochemical model combination. We compared the simulated fluxes with observed fluxes from a fertilized and drained peat soil with grass. <br><br> The results of this study showed that aggregates strongly affect N<sub>2</sub>O emissions: peak emissions are lower, whereas the background emissions are slightly higher. Implementation of the effect of aggregates caused a decrease in the simulated annual emissions of more than 40%. The new parameterization also significantly improved the model performance to simulate observed N<sub>2</sub>O fluxes. Aggregates have more impact on the reduction of N<sub>2</sub>O than on the production of N<sub>2</sub>O. Reduction of N<sub>2</sub>O is more sensitive to changes in the drivers than production of N<sub>2</sub>O and is in that sense the key process to understand N<sub>2</sub>O emissions from denitrification. The effects of changing conditions on reduction of N<sub>2</sub>O relative to N<sub>2</sub>O production is dependent on the NO<sub>3</sub> content of the soil. It is expected that in soils with a low NO<sub>3</sub> content the influence of aggregates on the NO<sub>3</sub> concentration is not negligible. This study showed that the current knowledge of the hydrological, biogeochemical and physical processes is sufficient to understand the observed N<sub>2</sub>O fluxes from a fertilized peatland. Further research is needed to test how aggregates affect the N<sub>2</sub>O fluxes in areas or periods with little NO<sub>3</sub> in the soil.

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