N₂O is the third most important GHG after carbon dioxide (CO₂) and methane (CH₄). Nevertheless, N₂O has a major impact on global warming because it is 25 times more "warming" than CH₄ and 265 times more than CO₂. On a global scale, agriculture is the largest source of N₂O emissions caused by human activity.

The return of crop residues to soil after harvest, such as wheat straw or rapeseed stalks, or the destruction of plant cover, such as catch crops or grasslands, are practices that maintain the stock of soil organic matters and recycle nutrients for the next crops in the rotation. However, N₂O emissions are associated with the decomposition of residues, and are produced by the two main pathways of nitrification and denitrification performed by soil microorganisms.

This study was carried out within the ResidueGas project associating INRAE with 9 European partners. Experiments were conducted under controlled laboratory conditions in two soils with residues of 9 plant species, covering a wide range of chemical nature and physiological maturity.

The results showed N₂O emissions from crop residues can be explained by the content of easily biodegradable carbon (the soluble fraction that composes the interior of plant cells). These compounds disappear during the physiological maturity of the plant tissues, when the cell walls become enriched in lignin and cellulose. The most immature residues emitted the most N₂O. For these residues, the cumulative net N₂O emitted after 60 days was around 5 kg N-N₂O ha^-1 for mustard, 3 kg N-N₂O ha^-1 for sugar beet and red clover, equivalent to 2 to 4 t ha^-1 of CO₂ equivalent emitted. The other residues had much lower emissions, less than 0.2 kg N-N₂O ha^-1. Further studies under different soil, climate and management conditions are needed to assess this impact on GHG emissions in relation to the other ecosystem services that these residues provide.

This work was supported by the ERA-NET FACCE ERA-GAS from the European Union’s Horizon (No. 696356). The French funding grant number was ANR-17-EGAS-0003

Read:

Lashermes, G., Recous, S., Alavoine, G., Janz, B., Butterbach-Bahl, K., Ernfors, M., Laville, P. (2022) The N₂O emission from decomposing crop residues is strongly linked to their initial soluble fraction and early mineralization dynamics. Science of the Total Environment, 806, 150883. https://doi.org/10.1016/j.scitotenv.2021.150883

Janz, B., Havermann, F., Lashermes, G., Zuazo, P., Engelsberger, F., Torabi, S.M., Butterbach-Bahl, K. (2021) Effects of crop residue incorporation and properties on combined soil gaseous N₂O, NO, and NH₃ emissions—A laboratory-based measurement approach. Science of The Total Environment, 151051. Open Access https://doi.org/10.1016/j.scitotenv.2021.151051

Lashermes, G., Recous, S., Alavoine, G., 2022. A delicate balance: Should we return green crop residues to the soil? Research Outreach! Issue 128, 48-52. Website

The data of this study are open and are available on the INRAE Data warehouse:

Lashermes, G., Recous, S., Gonzague, A., Janz, B., Butterbach-Bahl, K., Ernfors, M., Laville, P., (2021) Data for: Decomposition and N₂O emissions of nine crop residues incubated under controlled conditions in two soils, V1 ed. Portail Data INRAE. Open Access https://doi.org/10.15454/8ASYPC

Oral presentation:

Gwenaëlle Lashermes, Sylvie Recous, Gonzague Alavoine, Baldur Janz, Klaus Butterbach-Bahl, et al.. Nitrous oxide (N₂O) emissions from decomposing crop residues in soils. The ICOS France Science day, Oct 2021, Reims, France.

Contact : Dr Gwenaëlle Lashermes gwenaëlle.lashermes@inrae.fr, Dr. Sylvie Recous sylvie.recous@inrae.fr