Source partitioning using N2O isotopomers and soil WFPS to establish dominant N2O production pathways from different pasture sward compositions

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) emitted from agricultural soils and influenced by nitrogen (N) fertiliser management weather soil conditions. Source partitioning N2O emissions related to practices conditions could suggest effective mitigation strategies. Multispecies swards can maintain herbage yields at reduced N rates compared grass monocultures may reduce losses the wider environment. A restricted-simplex centroid experiment was used measure daily fluxes associated isotopomers eight experimental plots (7.8 m2) post urea-N application (40 kg ha−1). Experimental pastures consisted of differing proportions grass, legume forage herb represented perennial ryegrass (Lolium perenne), white clover (Trifolium repens) ribwort plantain (Plantago lanceolata), respectively. were measured using cavity ring down spectroscopy (CRDS) instrument adapted with small sample isotope module (SSIM) for analysis samples ≤20 mL. Site preference (SP = δ15Nα – δ15Nβ) δ15Nbulk ((δ15Nα + / 2) values attribute production nitrification, denitrification or mixture both nitrification over range WFPS (%). Daily ranged 8.26 86.86 g N2O-N ha−1 d−1. Overall, 34.2% attributed 29.0% 36.8% both. significant diversity effect on predicted SP indicated that inclusion decrease emission through biological inhibition under drier (31%–75% WFPS). Likewise, sharp decline in indicates increased content increase elevated moisture (43%–77% Biological grassland source timing match be useful