# Contribution of livestock to organic agriculture: modelling nitrogen flows at the national scale

Fanny Vergely, Aurélie Wilfart, Joël Aubin, Souhil Harchaoui

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Fanny Vergely, Aurélie Wilfart, Joël Aubin, Souhil Harchaoui. Contribution of livestock to organic agriculture: modelling nitrogen flows at the national scale. XXII International Nitrogen Workshop, Jun 2024, Aarhus, Denmark. hal-05224437

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https://hal.inrae.fr/hal-05224437v1

Submitted on 26 Aug 2025

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Distributed under a Creative Commons Attribution 4.0 International License
**Contribution of livestock to organic agriculture: modelling nitrogen flows at the national scale**

Fanny Vergely¹*, Aurélie Wilfart¹, Joël Aubin¹, Souhil Harchaoui¹

¹INRAE, Institut Agro Rennes-Angers, UMR SAS, 65 rue de Saint-Brieuc, 35042 Rennes, France

*Corresponding author: fanny.vergely@inrae.fr

The European Green Deal aims to expand the area of organic agriculture (OA) to 25% of agricultural land by 2030, compared to 9.9% at present. Recent studies that proposed scenarios for expanding OA have shown that nitrogen would be a major limiting factor (Barbieri et al., 2021), as the only source of nitrogen available to OA is biological nitrogen fixation by legume crops. In all scenarios, the number of livestock decrease compared to the present number, but livestock are necessary due to their dual function as a source of animal protein for food security and as a vector of circularity of nitrogen flows to cropland (Billen et al., 2021). There is an interest in quantifying the current state of nitrogen flows in OA at the national scale and highlighting the contribution of livestock to them to understand OA's capacity to develop within biophysical constraints.

We calibrated the ALPHA model (Chatzimpiros and Harchaoui, 2023) to simulate nitrogen flow and cycling in the national organic agri-food system of France, which has the largest area of OA in Europe.

The main inputs of nitrogen to OA in France were biological nitrogen fixation (51%), followed by atmospheric deposition (27%), conventional manure (11%) and organic feed imported from abroad (11%). Approximately 35% of the manure used to fertilise organic cropland came from conventional agriculture. Imported feed was used mainly to meet the nutritional requirements of monogastric animals (37% of total feed nitrogen) and, to a lesser extent, ruminants (6%). This study quantified the degree to which OA depends on external nitrogen inputs, which may limit its development.

Barbieri, P., Pellerin, S., Seufert, V., Smith, L., Ramankutty, N., Nesmé, T., 2021. Global option space for organic agriculture is delimited by nitrogen availability. NatureFood 12 p. https://doi.org/10.1038/s43016-021-00276-y

Billen, G., Aguilera, E., Einarsson, R., Garnier, J., Gingrich, S., Grizzetti, B., Lassaletta, L., Le Noë, J., Sanz-Cobena, A., 2021. Reshaping the European agro-food system and closing its nitrogen cycle: The potential of combining dietary change, agroecology, and circularity. One Earth 4, 839-850. https://doi.org/10.1016/j.oneear.2021.05.008

Chatzimpiros, P., Harchaoui, S., 2023. Sevenfold variation in global feeding capacity depends on diets, land use and nitrogen management. NatureFood 4, 372-383. https://doi.org/10.1038/s43016-023-00741-w