title: High-Resolution Denitrification Kinetics in Pasture Soils Link N2O Emissions to pH, and Denitrification to C Mineralization.
abstract: Denitrification in pasture soils is mediated by microbial and physicochemical processes leading to nitrogen loss through the emission of N2O and N2. It is known that N2O reduction to N2 is impaired by low soil pH yet controversy remains as inconsistent use of soil pH measurement methods by researchers, and differences in analytical methods between studies, undermine direct comparison of results. In addition, the link between denitrification and N2O emissions in response to carbon (C) mineralization and pH in different pasture soils is still not well described. We hypothesized that potential denitrification rate and aerobic respiration rate would be positively associated with soils. This relationship was predicted to be more robust when a high resolution analysis is performed as opposed to a single time point comparison. We tested this by characterizing 13 different temperate pasture soils from northern and southern hemispheres sites (Ireland and New Zealand) using a fully automated-high-resolution GC detection system that allowed us to detect a wide range of gas emissions simultaneously. We also compared the impact of using different extractants for determining pH on our conclusions. In all pH measurements, soil pH was strongly and negatively associated with both N2O production index (IN2O) and N2O/(N2O+N2) product ratio. Furthermore, emission kinetics across all soils revealed that the denitrification rates under anoxic conditions (NO+N2O+N2 μmol N/h/vial) were significantly associated with C mineralization (CO2 μmol/h/vial) measured both under oxic (r2 = 0.62, p = 0.0015) and anoxic (r2 = 0.89, p<0.0001) conditions.
authors.affiliation: Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand.
authors.forename: Md Sainur
authors.initials: MS
authors.lastname: Samad
authors.affiliation: Department of Environmental Sciences, Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Lars R
authors.initials: LR
authors.lastname: Bakken
authors.affiliation: Department of Environmental Sciences, Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Shahid
authors.initials: S
authors.lastname: Nadeem
authors.affiliation: Department of Soil and Physical Sciences, Lincoln University, Lincoln, New Zealand.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Clough
authors.affiliation: AgResearch Invermay, Mosgiel, New Zealand.
authors.forename: Cecile A M
authors.initials: CA
authors.lastname: de Klein
authors.affiliation: Teagasc, Environmental Research Centre, Johnstown Castle, Wexford, Ireland.
authors.forename: Karl G
authors.initials: KG
authors.lastname: Richards
authors.affiliation: Teagasc, Environmental Research Centre, Johnstown Castle, Wexford, Ireland.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Lanigan
authors.affiliation: Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand.
authors.forename: Sergio E
authors.initials: SE
authors.lastname: Morales
mesh_terms: D000693:Anaerobiosis / Q000502:physiology; D002244:Carbon / Q000378:metabolism*; D058440:Denitrification / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009609:Nitrous Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D012987:Soil; D009569:Nitric Oxide; D002244:Carbon; D009609:Nitrous Oxide; D009584:Nitrogen; D010100:Oxygen