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www.biogeosciences-discuss.net/5/4699/2008/
doi:10.5194/bgd-5-4699-2008
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
Ammonia fluxes in relation to cutting and fertilization of an intensively managed grassland derived from an inter-comparison of gradient measurements
1Centre for Ecology and Hydrology (Edinburgh Research Station), Bush Estate, Penicuik, Midlothian, EH26 0QB, UK
2Institute of Atmospheric Physics, P.O. Box 39, 1675, Budapest, Hungary
3Institut fur Agrarokologie, Bundesforschungsanstalt fur Landwirtschaft (FAL), Bundesallee 50, 38 116 Braunschweig, Germany
4Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, 8046 Zürich, Switzerland
Abstract. Quantification of ammonia (NH3) land-atmosphere exchange is required for atmospheric modelling and assessment of nitrogen deposition, yet flux measurement methods remain highly uncertain. To address this issue, a major inter-comparison of ammonia fluxes over intensively managed grassland was conducted during the GRAMINAE Integrated Experiment held in Braunschweig, Germany. In order to provide a robust dataset of ammonia exchange with the vegetation, four independent continuous flux gradient systems were operated. Three independently operated continuous wet denuders systems (AMANDA) were compared with a Wet Effluent Diffusion Denuder (mini-WEDD) system. Measurements were made at two distances from an adjacent livestock farm, allowing effects of advection to be quantified in a real landscape setting. Data treatment included filtering for instrument failure, disturbed wind sectors and unsuitable micrometeorological conditions, with corrections made for storage and advection errors.
The inter-comparison demonstrated good agreement in measured ammonia concentrations and fluxes (<20% difference) for some periods, although the performance of the ammonia analyzers was variable, with much poorer agreement on particular days. However, by using four systems, the inter-comparison was able to provide a robust mean estimate of continuous ammonia fluxes through the experiment. The observed fluxes were: a) small bi-directional fluxes prior to cutting (−64 to 42 ng NH3 m−2 s−1), b) larger diurnally-varying emissions following cutting (−49 to 703 ng NH3 m−2 s−1) and c) much larger emissions following fertilizer application (0 to 3820 ng NH3 m−2 s−1). The results are a salutary reminder of the uncertainty in unreplicated ammonia flux measurements, while the replication of the present study provides a uniquely robust dataset for the evaluation of ammonia exchange processes. It is clear that consistently reliable determination of ammonia concentrations remains the major measurement challenge.
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Citation: Milford, C., Theobald, M. R., Nemitz, E., Hargreaves, K. J., Horvath, L., Raso, J., Dämmgen, U., Neftel, A., Jones, S. K., Hensen, A., Loubet, B., Cellier, P., and Sutton, M. A.: Ammonia fluxes in relation to cutting and fertilization of an intensively managed grassland derived from an inter-comparison of gradient measurements, Biogeosciences Discuss., 5, 4699-4744, doi:10.5194/bgd-5-4699-2008, 2008. Bibtex EndNote Reference Manager XML
