Issifou Amadou, a PhD student specializing in the study of soil science, bio-geochemistry and agroecology, member of the AGHYLE research unit, validated his PhD thesis following his defense on Tuesday, December 20, 2022, which took place in Beauvais.

His work focused on the "role of organic phosphorus forms, soil minerals, nitrogen and plant functional traits on the availability and acquisition of phosphorus by plants for an optimal management of organic fertilizers in agroecosystems".

The whole UniLaSalle team congratulates Issifou for obtaining his thesis!

Abstract

Phosphorus (P) deficiency in soils limits the productivity of many agroecosystems.

Modern agricultural practices rely heavily on mineral fertilizers derived from mined phosphate rock, a limited and constantly diminishing resource. In the perspective of a more sustainable management of P nutrition in agroecosystems, organic phosphorus (OP) from organic and soil inputs is increasingly considered as a complement to mineral P fertilizers.

However, the dynamics of P supply through organic fertilizer are not always well understood. We have shown that factors related to soil mineral properties and molecular characteristics of OPs directly affected the reactions of OPs and their release into the soil.

Similarly, these factors affected the availability of OPs in the rhizosphere and their uptake by the plant. By characterizing N-OP-mineral interactions we had provided important information on ecosystem P cycling under N addition and the biogeochemical properties involved, which will allow ecosystem models to accurately predict plant N-P limitation and its impacts, and will also help build robust ecosystem models with fully coupled N-P or C-N-P interactions.

The positive response of P acquisition strategies to PO sources has resulted in greater P availability and acquisition from POs. Finally, the identification through modeling of major traits involved in P acquisition strategies and their ability to better predict P acquisition, offers opportunities to design crop species compositions and more specifically the functional structure of crop plant communities.

These systems would in turn allow the assessment of the overall effects of organic input, soil and plant interactions on P availability and support farmers' management decisions, such as appropriate P fertilization.

Jury :

Mr. Sylvain PELLERIN, Director of Research HDR, INRAE President

Mrs. Cornelia RUMPEL, Research Director HDR, CNRS Rapporteur

Mrs. Claude PLASSARD, Director of Research HDR, INRAE Rapporteur

Mr. Frédéric GERARD, Research Fellow, HDR, INRAE Examiner

Mr. Olivier POURRET, Teacher-researcher, HDR, UniLaSalle Examiner

Mr. Michel-Pierre FAUCON, Teacher-researcher, HDR, UniLaSalle Thesis Director

Mr. David HOUBEN, Teacher-researcher, UniLaSalle Co-supervisor