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Bonjour à tous,

J’ai le plaisir de vous annoncer la soutenance de ma thèse intitulée « Long-term effects of repeated inputs of organic wastes in agriculture on crop production and soil fertility: insights from two French long term field experiments », menée au sein de l’UMR ECOSYS.

La soutenance sera en anglais et aura lieu le lundi 5 juin 2023 à 10h, à AgroParisTech, 22 place de l’Agronomie, Palaiseau (91120) dans l’amphithéâtre Pal-C2.0.37.

Elle sera également retransmise par visioconférence, au lien suivant :

https://inrae-fr.zoom.us/j/99833478995

Composition du jury

Lionel JORDAN-MEILLE - Maître de Conférences (HDR), Bordeaux Sciences Agro (Rapporteur & Examinateur)

Tusheng REN - Professeur, China Agricultural University (Rapporteur & Examinateur)

Yves COQUET - Professeur, AgroParisTech (Université Paris-Saclay) (Examinateur)

Marie-Liesse VERMEIRE- Chercheuse, CIRAD (Examinatrice)

Encadrement de la thèse

Sabine HOUOT - Directrice de Recherche (directrice de thèse)

Florent LEVAVASSEUR - Ingénieur de Recherche (co-encadrant)

Abstract :

Fertilizers play a crucial role in ensuring global food security. However, mineral fertilizer production relies on non-renewable resources, and their excessive use result in environmental and health issues. Recycling organic waste (OW) in agriculture can improve soil fertility and substitute mineral fertilizers. This work aims to assess the long-term effects of repeated applications of OW in agriculture and their driving factors. We used two French long-term field experiments testing various OW representative of frequently used OW in periurban agriculture (urban composts, farmyard manure and sewage sludge) with two different cropping system, soil and climate conditions. Specifically, we investigated i) the dynamics of crop yields and soil properties, ii) the driving factors behind changes in crop yields and soil properties, and iii) the differences of the effects between the different types of OW and the two sites. Overall, our study has shown the potential benefits and limitations of using OW in agriculture. Long-term applications of OW mainly improve soil chemical fertility without negatively impacting soil biological activity. The extent to which OW can improve soil properties may be constrained in soils that are already fertile. A partial substitution of mineral fertilizers is possible without decreasing crop yields. However, applying OW alone at European regulatory rates may not be sufficient for achieving optimal yields. Additionally, the influence of OW application on soil properties and crop yield heavily depends on several factors, especially on the input fluxes of carbon and nutrients related to the type of OW and to the application rate, and on the initial soil properties. Nevertheless, integrating OW recycling into a wider range of sustainable agricultural practices can be a judicious strategy for enhancing soil fertility and improving crop productivity.

Cordialement,

Haotian Chen