Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 6 5 2009 10.5194/bg-6-819-2009 http://www.biogeosciences.net/6/819/2009/ http://www.biogeosciences.net/6/819/2009/bg-6-819-2009.html http://www.biogeosciences.net/6/819/2009/bg-6-819-2009.pdf 819 834 2009-05-15 Ammonia fluxes in relation to cutting and fertilization of an intensively managed grassland derived from an inter-comparison of gradient measurements C. Milford cmilford@inm.es M. R. Theobald E. Nemitz K. J. Hargreaves L. Horvath J. Raso U. Dämmgen A. Neftel S. K. Jones A. Hensen B. Loubet P. Cellier M. A. Sutton Centre for Ecology and Hydrology (Edinburgh Research Station), Bush Estate, Penicuik, Midlothian, EH26 0QB, UK Institute of Atmospheric Physics, P.O. Box 39, 1675 Budapest, Hungary Institut für Agrarökologie, Bundesforschungsanstalt für Landwirtschaft (FAL), Bundesallee 50, 38116 Braunschweig, Germany Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, 8046 Zurich, Switzerland Energy research Centre of the Netherlands (ECN), Postbus 1, 1755 ZG Petten, The Netherlands Institut National de la Recherche Agronomique (INRA), UMR Environnement et Grandes Cultures, Thiverval-Grignon, 78850, France now at: Institute of Earth Sciences "Jaume Almera", CSIC, C/Lluis Solé i Sabarís s/n, Barcelona, 08028, Spain 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. <br><br> The inter-comparison demonstrated good agreement in measured ammonia concentrations and fluxes (relative standard error <20%) for some periods, although the performance of the ammonia analyzers were variable, with much poorer agreement on particular days. 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