Mitigation potential of soil carbon management overestimated by neglecting N2O emissions

Abstract

International initiatives such as the ‘4 per 1000’ are promoting enhanced carbon (C) sequestration in agricultural soils as a way to mitigate greenhouse gas emissions1. However, changes in soil organic C turnover feed back into the nitrogen (N) cycle2, meaning that variation in soil nitrous oxide (N2O) emissions may offset or enhance C sequestration actions3. Here we use a biogeochemistry model on approximately 8,000 soil sampling locations in the European Union4 to quantify the net CO2 equivalent (CO2e) fluxes associated with representative C-mitigating agricultural practices. Practices based on integrated crop residue retention and lower soil disturbance are found to not increase N2O emissions as long as C accumulation continues (until around 2040), thereafter leading to a moderate C sequestration offset mostly below 47% by 2100. The introduction of N-fixing cover crops allowed higher C accumulation over the initial 20 years, but this gain was progressively offset by higher N2O emissions over time. By 2060, around half of the sites became a net source of greenhouse gases. We conclude that significant CO2 mitigation can be achieved in the initial 20–30 years of any C management scheme, but after that N inputs should be controlled through appropriate management.

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Fig. 1: Temporal trend of cumulative CO2 sequestration in soil, N2O emissions and net GHG soil flux, under the mitigation practices in comparison with the baseline.
Fig. 2: Net soil GHG flux of mitigation practices in comparison with the baseline by 2040.
Fig. 3: Effect of mitigation practices on crop responses and relationship with N input sources.

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Acknowledgements

The work was carried out as part of the JRC’s Institutional Work Programme under the Natural Capital Soil Project (Project 702), Work Package 5037 ‘Soil for Climate Change’. The LUCAS Survey is undertaken by the EU Statistical Office (EUROSTAT) and supported by the JRC for the soil component.

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E.L. developed the research concepts and conducted the modelling and analyses. E.L., A.L. and A.J. performed the data interpretation. E.L. took the lead on writing the paper with contributions from A.L. and A.J.

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Correspondence to Emanuele Lugato.

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Lugato, E., Leip, A. & Jones, A. Mitigation potential of soil carbon management overestimated by neglecting N2O emissions. Nature Clim Change 8, 219–223 (2018). https://doi.org/10.1038/s41558-018-0087-z

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