Jianlin Shen1, Deli Chen2, Mei Bai2, Jianlei Sun2, Trevor Coates2, Shu Kee Lam2, Yong Li1
1 Key Laboratory of Agro-Ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China (E-mail: jlshen@isa.ac.cn)
2 Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010, Australia (Email: delichen@unimelb.edu.au)
Abstract
We conducted the first study in Australia to measure ammonia (NH3) deposition within 1 km from a commercial beef feedlot in Victoria. NH3 concentrations and deposition fluxes decreased exponentially with distance away from the feedlot. The mean NH3 concentrations decreased from 419 µg N m-3 at 50 m to 36 µg N m-3 at 1 km, while the mean NH3 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 NH3 deposition of 53.9 tonne N yr-1 in the area within 1 km from the feedlot, accounting for 8% of the annual NH3-N emissions from the feedlot. This high NH3 deposition rate nearby the cattle feedlot had caused the increase of soil inorganic nitrogen content, especially for NO3– (from 33 mg N kg-1 at 1000 m from the feedlot to 124 mg N kg-1 at 50 m from the feedlot). Higher N content (4.0% to 5.7%) in the above-ground part of grassland species and high cover rate of single species (e.g. a cover rate of 31% to 42% at 50 to 200 m from the feedlot for Cymbonotus lawsonianus) were found in the grassland transect to the southeast of the feedlot. Our results suggest that NH3 deposition is significant nitrogen (N) nutrient input for surrounding croplands and natural ecosystems.