Ammonia deposition in the neighbourhood of an intensive cattle feedlot in Victoria, Australia

Intensive cattle feedlots are large emission sources of ammonia (NH(3)), but NH(3) deposition to the landscape downwind of feedlots is not well understood. We conducted the first study in Australia to measure NH(3) dry deposition within 1 km of a commercial beef cattle feedlot in Victoria. NH(3) concentrations and deposition fluxes decreased exponentially with distance away from the feedlot. The mean NH(3) concentrations decreased from 419 μg N m(−3) at 50 m to 36 μg N m(−3) at 1 km, while the mean NH(3) dry deposition fluxes decreased from 2.38 μg N m(−2) s(−1) at 50 m to 0.20 μg N m(−2) s(−1) at 1 km downwind from the feedlot. These results extrapolate to NH(3) deposition of 53.9 tonne N yr(−1) in the area within 1 km from the feedlot, or 67.5 kg N ha(−1) yr(−1) as an area-weighted mean, accounting for 8.1% of the annual NH(3)-N emissions from the feedlot. Thus NH(3) deposition around feedlots is a significant nitrogen input for surrounding ecosystems. Researches need be conducted to evaluate the impacts of NH(3) deposition on the surrounding natural or semi-naturals ecosystems and to reduce N fertilizer application rate for the surrounding crops by considering nitrogen input from NH(3) deposition.