24 October - FARE contributes to an opinion paper on the N2O emissions

24 October - FARE contributes to an opinion paper on the N2O emissions

24 October - FARE contributes to an opinion paper on the N2O emissions

The return of crop residues to the soil after harvesting, such as cereal straw or the destruction of plant cover crops, maintains the soil's stock of organic matter and recycles nitrogen for subsequent crops. However, nitrous oxide (N2O) emissions are associated with the decomposition of residues, during the nitrification and denitrification processes by soil micro-organisms.

As the current method used by the IPCC (Intergovernmental Panel on Climate Change) to inventory emissions of N2O, a potent greenhouse gas (GHG), considers nitrogen inputs from crop residues as the sole factor determining N2O emissions, it does not take other factors into account. Yet there is irrefutable evidence that emissions vary considerably between residues with different biochemical and physical characteristics, in particular the concentration of mineral or easily mineralised nitrogen and the concentration of soluble carbon in residues, which increase the soil's potential to produce N2O.  High concentrations of these components are associated with residues returned to the soil from plants at immature physiological stages (e.g. cover crops, grasses and legumes, and vegetable residues) as opposed to residues from plants that have reached physiological maturity (e.g. cereal straw). A more accurate estimate of the short-term effects (a few months) of crop residues on N2O emissions could involve distinguishing between mature and immature crop residues, which have markedly different emission factors. 

There is an urgent need for more targeted mitigation efforts for N2O emissions after crop residues have been added to the soil, which requires an improved methodology for accounting for emissions. More needs to be known about N2O emissions associated with agricultural practices in order to improve the GHG balance for agriculture.

This opinion paper stems from the work of the European ResidueGas project, coordinated by Aarhus University and involving INRAE and 9 European partners (https://projects.au.dk/residuegas). This work was supported by the FACCE ERA-GAS of the European Union's Horizon programme (n° 696356). The French grant was provided by the ANR (ANR-17-EGAS-0003).

Read: Olesen JE et al. Challenges of accounting nitrous oxide emissions from agricultural crop residues. Global Change Biology 2023, 1–10. https://doi.org/10.1111/gcb.16962

Contacts: Sylvie Recous (sylvie.recous@inrae.fr), Gwenaëlle Lashermes (gwenaelle.lashermes@inrae.fr), Pascal Thiébeau (pascal.thiebeau@inrae.fr)

Modification date : 24 October 2023 | Publication date : 24 October 2023 | Redactor : S. Recous / G. Lashermes / P. Thiébeau / G. Paës