Summary
This laboratory incubation study examined how soil saturation influences denitrification and nitrification processes in grassland soil, with particular attention to the interaction between water content and soil compaction at the micropore scale. The authors found that flux variability was greater in less saturated soils, likely due to nutrient distribution heterogeneity from soil cracking and nutrient hotspots; isotopic evidence indicated denitrification dominated at highest saturation whilst nitrification may have contributed at lower moisture levels (71% WFPS). The results revealed two distinct nitrogen pools with different dynamics: added nitrogen produced intense denitrification whilst soil-derived nitrogen showed less isotopic fractionation.
UK applicability
These findings are directly applicable to UK grassland management, as the study was conducted on a UK grassland soil and addresses how agricultural practices affecting soil structure and water content (compaction, drainage, rainfall patterns) influence greenhouse gas emissions. The results have implications for UK agricultural policy on nitrous oxide mitigation and soil management in pastoral systems.
Key measures
Nitrous oxide (N2O) flux; dinitrogen (N2) flux; water-filled pore space (WFPS); N2O isotopocules (delta-15N, delta-18O); relative contribution of denitrification and nitrification pathways
Outcomes reported
The study measured emissions of nitrous oxide (N2O) and dinitrogen (N2) gas from grassland soil incubated at different saturation levels, and analysed isotopocules of N2O to determine the sources and pathways of nitrogen loss. Flux variability, soil water content (water-filled pore space), and the relative contribution of denitrification versus nitrification were characterised across moisture conditions.
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