Evaluating the Potential of Legumes to Mitigate N2O Emissions From Permanent Grassland Using Process-Based Models

Kathrin Fuchs*, Lutz Merbold, Nina Buchmann, Gianni Bellocchi, Marco Bindi, Lorenzo Brilli, Richard T. Conant, Christopher D. Dorich, Fiona Ehrhardt, Nuala Fitton, Peter Grace, Katja Klumpp, Mark Liebig, Mark Lieffering, Raphaël Martin, Russell McAuliffe, Paul C.D. Newton, Robert M. Rees, Sylvie Recous, Pete SmithJean François Soussana, Cairistiona F.E. Topp, Val Snow

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

A potential strategy for mitigating nitrous oxide (N2O) emissions from permanent grasslands is the partial substitution of fertilizer nitrogen (Nfert) with symbiotically fixed nitrogen (Nsymb) from legumes. The input of Nsymb reduces the energy costs of producing fertilizer and provides a supply of nitrogen (N) for plants that is more synchronous to plant demand than occasional fertilizer applications. Legumes have been promoted as a potential N2O mitigation strategy for grasslands, but evidence to support their efficacy is limited, partly due to the difficulty in conducting experiments across the large range of potential combinations of legume proportions and fertilizer N inputs. These experimental constraints can be overcome by biogeochemical models that can vary legume-fertilizer combinations and subsequently aid the design of targeted experiments. Using two variants each of two biogeochemical models (APSIM and DayCent), we tested the N2O mitigation potential and productivity of full factorial combinations of legume proportions and fertilizer rates for five temperate grassland sites across the globe. Both models showed that replacing fertilizer with legumes reduced N2O emissions without reducing productivity across a broad range of legume-fertilizer combinations. Although the models were consistent with the relative changes of N2O emissions compared to the baseline scenario (200 kg N ha−1 yr−1; no legumes), they predicted different levels of absolute N2O emissions and thus also of absolute N2O emission reductions; both were greater in DayCent than in APSIM. We recommend confirming these results with experimental studies assessing the effect of clover proportions in the range 30–50% and ≤150 kg N ha−1 yr−1 input as these were identified as best-bet climate smart agricultural practices.

Original languageEnglish
Article numbere2020GB006561
Number of pages20
JournalGlobal Biogeochemical Cycles
Volume34
Issue number12
Early online date26 Nov 2020
DOIs
Publication statusPublished - Dec 2020

Keywords

  • biological nitrogen fixation
  • greenhouse gas mitigation
  • legumes

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