title: Biochar and denitrification in soils: when, how much and why does biochar reduce N₂O emissions?
abstract: Agricultural soils represent the main source of anthropogenic N2O emissions. Recently, interactions of black carbon with the nitrogen cycle have been recognized and the use of biochar is being investigated as a means to reduce N2O emissions. However, the mechanisms of reduction remain unclear. Here we demonstrate the significant impact of biochar on denitrification, with a consistent decrease in N2O emissions by 10-90% in 14 different agricultural soils. Using the (15)N gas-flux method we observed a consistent reduction of the N2O/(N2 + N2O) ratio, which demonstrates that biochar facilitates the last step of denitrification. Biochar acid buffer capacity was identified as an important aspect for mitigation that was not primarily caused by a pH shift in soil. We propose the function of biochar as an "electron shuttle" that facilitates the transfer of electrons to soil denitrifying microorganisms, which together with its liming effect would promote the reduction of N2O to N2.
authors.affiliation: Department of Soil and Water Conservation and Waste Management, CEBAS-CSIC, Campus Universitario de Espinardo, 30100 Murcia, Spain. mlcayuela@cebas.csic.es
authors.forename: Maria Luz
authors.initials: ML
authors.lastname: Cayuela
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Sánchez-Monedero
authors.forename: Asunción
authors.initials: A
authors.lastname: Roig
authors.forename: Kelly
authors.initials: K
authors.lastname: Hanley
authors.forename: Akio
authors.initials: A
authors.lastname: Enders
authors.forename: Johannes
authors.initials: J
authors.lastname: Lehmann
mesh_terms: D000383:Agriculture / Q000379:methods; D002606:Charcoal / Q000737:chemistry*; D058440:Denitrification; D005740:Gases / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry; D009609:Nitrous Oxide / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*
chemical_list: D005740:Gases; D012987:Soil; C540010:biochar; D002606:Charcoal; D009609:Nitrous Oxide; D009584:Nitrogen