Effect of soil saturation on denitrification in a grassland soil

Laura Maritza Cardenas, Roland Bol, Dominika Lewicka-Szczebak, Andrew Stuart Gregory, Graham Peter Matthews, William Richard Whalley, Thomas Henry Misselbrook, David Scholefield, Reinhard Well
2017 Biogeosciences  
<p><strong>Abstract.</strong> Nitrous oxide (N<sub>2</sub>O) is of major importance as a greenhouse gas and precursor of ozone (O<sub>3</sub>) destruction in the stratosphere mostly produced in soils. The soil-emitted N<sub>2</sub>O 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
more » ... e 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 N<sub>2</sub>O and N<sub>2</sub> were measured as well as the isotopocules of N<sub>2</sub>O. 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<span class="thinspace"></span>% 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.</p>
doi:10.5194/bg-14-4691-2017 fatcat:wnzrf2in4rd2lbzlfuuopaonk4