Biochar incorporation into pasture soil suppresses in situ nitrous oxide emissions from ruminant urine patches.

468 Nitrous oxide (N2O) emissions from grazing animal excreta are estimated to be responsible for 1.5 Tg of the total 6.7 Tg of anthropogenic N2O emissions. Th is study was conducted to determine the in situ eff ect of incorporating biochar, into soil, on N2O emissions from bovine urine patches and associated pasture uptake of N. Th e eff ects of biochar rate (0–30 t ha−1), following soil incorporation, were investigated on ruminant urine-derived N2O fl uxes, N uptake by pasture, and pasture yield. During an 86-d spring-summer period, where irrigation and rainfall occurred, the N2O fl uxes from 15N labeled ruminant urine patches were reduced by >50%, after incorporating 30 t ha−1 of biochar. Taking into account the N2O emissions from the control plots, 30 t ha−1 of biochar reduced the N2O emission factor from urine by 70%. Th e atom% 15N enrichment of the N2O emitted was lower in the 30 t ha −1 biochar treatment, indicating less urine-N contributed to the N2O fl ux. Soil NO3 −-N concentrations were lower with increasing biochar rate during the fi rst 30 d following urine deposition. No diff erences occurred, due to biochar addition, with respect to dry matter yields, herbage N content, or recovery of 15N applied in herbage. Incorporating biochar into the soil can signifi cantly diminish ruminant urine-derived N2O emissions. Further work is required to determine the persistence of the observed eff ect and to fully understand the mechanism(s) of the observed reduction in N2O fl uxes. Biochar Incorporation into Pasture Soil Suppresses in situ Nitrous Oxide Emissions from Ruminant Urine Patches