Beneficial effects of multi-species mixtures on N2O emissions from intensively managed grassland swards

• Published in: The Science of the total environment Vol. 792; p. 148163
• Main Authors: Cummins, Saoirse, Finn, John A., Richards, Karl G., Lanigan, Gary J., Grange, Guylain, Brophy, Caroline, Cardenas, Laura M., Misselbrook, Tom H., Reynolds, Christopher K., Krol, Dominika J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20-10-2021
• Subjects: GHG emissions; Grassland production; Grasslands; Multi-species mixtures; Nitrous oxide; Yield-scaled N2O emissions; GHG emissions; Grasslands; Nitrous oxide; Yield-scaled N2O emissions; Multi-species mixtures; Grassland production
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.148163

In a field experiment, annual nitrous oxide (N2O) emissions and grassland yield were measured across different plant communities, comprising systematically varying combinations of monocultures and mixtures of three functional groups (FG): grasses (Lolium perenne, Phleum pratense), legumes (Trifolium pratense, Trifolium repens) and herbs (Cichorium intybus, Plantago lanceolata). Plots received 150 kg ha−1 year−1 nitrogen (N) (150 N), except L. perenne monocultures which received two N levels: 150 N and 300 N. The effect of plant diversity on N2O emissions was derived from linear combinations of species performances' in monoculture (species identity) and not from strong interactions between species in mixtures. Increasing from 150 N to 300 N in L. perenne resulted in a highly significant increase in cumulative N2O emissions from 1.39 to 3.18 kg N2O-N ha−1 year−1. Higher N2O emissions were also associated with the legume FG. Emissions intensities (yield-scaled N2O emissions) from multi-species mixture communities around the equi-proportional mixture were lowered due to interactions among species. For N2O emissions scaled by nitrogen yield in forage, the 6-species mixture was significantly lower than L. perenne at both 300 N and 150 N. In comparison to 300 N L. perenne, the same N yield or DM yield could have been produced with the equi-proportional 6-species mixture (150 N) while reducing N2O losses by 63% and 58% respectively. Compared to 150 N L. perenne, the same N yield or DM yield could have been produced with the 6-species mixture while reducing N2O losses by 41% and 24% respectively. Overall, this study found that multi-species grasslands can potentially reduce both N2O emissions and emissions intensities, contributing to the sustainability of grassland production.
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•N2O emissions were driven by strong plant identity effects with no interspecific interactions.•The N yield-scaled N2O emissions of the 6-species mixture were 41% lower than the L. perenne monoculture (both at 150 kg ha−1 year−1 of nitrogen fertiliser).•The DM yield-scaled N2O emissions of the 6-species mixture were 24% lower than the L. perenne monoculture (both at 150 kg ha−1 year−1 of nitrogen fertiliser).