Summary
This laboratory study examined how isotope fractionation associated with N₂O reduction during denitrification affects the accuracy of site preference (SP) values used to partition N₂O sources in soils. Using three different correction models on 431 measurements from soil incubations, the authors demonstrated that a closed-system model with fixed isotope effects significantly overestimates the N₂O reduction effect on SP values, particularly at high reduction rates, whereas a dynamic apparent NIE function accounting for variable soil micropore reduction rates provides more reliable source partitioning estimates.
UK applicability
The methodological refinements described are directly applicable to UK soil science laboratories conducting N₂O source attribution studies, particularly for characterising denitrification in agricultural and grassland soils. Improved correction approaches could enhance the reliability of UK-based research on N₂O mitigation strategies in farming systems.
Key measures
N₂O site preference (SP) values (‰), N₂ and N₂O concentrations (gas chromatography), net isotope effects (NIE) during N₂O reduction, source contribution percentages from nitrification/fungal denitrification versus bacterial denitrification
Outcomes reported
The study quantified how isotope fractionation during N₂O reduction biases site preference (SP) values used to partition N₂O sources between nitrification and denitrification. Three correction models (closed-system, open-system, and dynamic apparent NIE function) were applied to 431 N₂O SP measurements from six soil incubation studies.
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