Effect of soil saturation on denitrification in a grassland soil
- 1Rothamsted Research, North Wyke, Okehampton, Devon EX20 2SB, UK
- 2Institute of Bio- and Geosciences, IBG-3/Agrosphere, Forschungszentrum Jülich GmbH, 52428 Jülich, Germany
- 3Thünen Institute of Climate-Smart Agriculture, Federal Research Institute for Rural Areas, Forestry and Fisheries, Bundesallee, 50, 38116 Braunschweig, Germany
- 4Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
- 5University of Plymouth, Drake Circus, Plymouth, Devon PL4 8AA, UK
Abstract. Nitrous oxide (N2O) is of major importance as a greenhouse gas and precursor of ozone (O3) destruction in the stratosphere mostly produced in soils. The soil-emitted N2O is generally predominantly derived from denitrification and, to a smaller extent, nitrification, both processes controlled by environmental factors and their interactions, and are influenced by agricultural management. Soil water content expressed as water-filled pore space (WFPS) is a major controlling factor of emissions and its interaction with compaction, has not been studied at the micropore scale. A laboratory incubation was carried out at different saturation levels for a grassland soil and emissions of N2O and N2 were measured as well as the isotopocules of N2O. We found that flux variability was larger in the less saturated soils probably due to nutrient distribution heterogeneity created from soil cracks and consequently nutrient hot spots. The results agreed with denitrification as the main source of fluxes at the highest saturations, but nitrification could have occurred at the lower saturation, even though moisture was still high (71 % WFSP). The isotopocules data indicated isotopic similarities in the wettest treatments vs. the two drier ones. The results agreed with previous findings where it is clear there are two N pools with different dynamics: added N producing intense denitrification vs. soil N resulting in less isotopic fractionation.