The relationship between ammonia emissions from a poultry farm and soil NO and N₂O fluxes from a downwind source

U. Skiba (1) , J. Dick (1) , R. Storeton-West (1) , S. Fernades-Lopez (2) , C. Wood (3) , S. Tang (1) , N. van Dijk (1)

1 CEH - Centre for Ecology and Hydrology [Edinburgh]
2 Dpto. Química y Análisis Agrícola-E.T.S.I. Agrónomos de Madrid
3 CEH Lancaster

Intensive livestock farms emit large concentrations of NH₃, most of which is deposited very close to the source. The presence of trees enhances the deposition. Rates to down wind forests can exceed 40 kg N ha^-1. The steep gradient in large NH₃ concentration and deposition at the edge of a downwind forest to background concentrations within a few hundred meters provides an ideal site to study the effect of different rates of N deposition on biological and chemical processes under similar environmental conditions. We have investigated the effect of different rates of NH₃ deposition (62, 45, 24 and 5 kg NH₃-N ha^-1 y^-1) on the flux of NO and N₂O from soil in a mixed woodland downwind of a large poultry farm (160000 birds) in Scotland, which has been operating for about 40 years. Measurements were carried out for a 6 month period, with hourly NO flux measurements, daily N₂O fluxes close to the farm and monthly at all sites and monthly cumulative wet and dry N deposition. The increased NH₃ and NH₄⁺ deposition to the woodland increased emissions of NO and N₂O and soil available NH₄⁺ and NO₃^- concentrations. Average NO and N₂O fluxes measured 15, 25 and 45 m downwind of the farm were 111.2±41.1, 123.3±40.7, 38.3±28.8 µg NO-N m^-2 h^-1 and 9.9±7.5, 34.3±33.3 and 21.2±6.1 µg N_O-N m^-2 h^-1, respectively. At the background site 270 m downwind the N₂O flux was reduced to 1.75±2.1 µg N₂O-N m^-2 h^-1. NO emissions were significantly influenced by seasonal and daily changes in soil temperature and followed a diurnal pattern with maximum emissions approximately 3h after noon. For N₂O no consistent diurnal pattern was observed. Changes in soil moisture content had a less clear effect on the NO and N₂O flux. On average the NO emissions expressed as a fraction of the elevated N deposited were 7.1% (at 15 m), 6% (at 25 m) and 2.3% (at 45 m) downwind of the farm, whereas for N₂O the emissions were only 2.8% (at 15 m), 3% (at 25 m) and 3% (at 45 m) downwind. These emission fractions exceed the emission factor of 1% advised by the IPCC for N₂O emissions resulting from atmospheric N deposition.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

U. Skiba, J. Dick, R. Storeton-West, S. Fernades-Lopez, C. Wood, et al.. The relationship between ammonia emissions from a poultry farm and soil NO and N₂O fluxes from a downwind source. Biogeosciences Discussions, 2005, 2 (4), pp.977-995. ⟨hal-00297782⟩