Greenhouse gas emissions from the grassy outdoor run of organic broilers

[摘要] Nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂)fluxes over the grassy outdoor run of organically grown broilers weremonitored using static chambers over two production batches in contrastedseasons. Measured N₂O and CH₄ fluxes were extremely variable intime and space for both batches, with fluxes ranging from a small uptake bysoil to large emissions peaks, the latter of which always occurred in thechambers located closest to the broiler house. In general, fluxes decreasedwith increasing distance to the broiler house, demonstrating that theforaging of broilers and the amount of excreted nutrients (carbon, nitrogen)largely control the spatial variability of emissions. Spatial integration bykriging methods was carried out to provide representative fluxes on theoutdoor run for each measurement day. Mechanistic relationships betweenplot-scale estimates and environmental conditions (soil temperature andwater content) were calibrated in order to fill gaps between measurementdays. Flux integration over the year 2010 showed that around3 ± 1 kg N₂O-N ha⁻¹ were emitted on the outdoor run, equivalent to0.9% of outdoor N excretion and substantially lower than the IPCC defaultemission factor of 2%. By contrast, the outdoor run was found to be a netCH₄ sink of about −0.56 kg CH₄-C ha⁻¹, though this sinkcompensated less than 1.5% (in CO₂ equivalents) of N₂Oemissions. The net greenhouse gas (GHG) budget of the outdoor run isexplored, based on measured GHG fluxes and short-term (1.5 yr) variations insoil organic carbon.

[学科分类] 地球化学与岩石