Résumé
A study was conducted in glasshouse conditions to assess the influences of the leguminous plant diversity on the soil microbial functions and their consequences on the wheat growth. Three legume species were targeted: faba bean, alfalfa and pea. All the combinations of one, two or three species were performed in pots filled with a P deficient soil collected from a field located near Marrakech (Morocco). After 3 months culture, the plants were harvested and the shoot and root parts were dried, weighed and analyzed for their N and P contents. The soil catabolic functions were measured using the SIR (Substrate Induced Respiration) method. The mycorrhizal soil infectivity was assessed according to Kisa et al. (2007) and the arbuscular mycorrhizal (AM) diversity was estimated by PCR/Sequencing. Fluorescent Pseudomonads (FP), known to have PGPR capacities have been enumerated, identified (PCR/sequencing) and characterized for their inorganic phosphate solubilizing activities and for their effect on wheat growth. The results showed that an increase of legume diversity involved: (i) significant differences between the microbial functions within the treatments, (ii) changes in the abundance and diversity of the AM communities, (iii) an increase of the FP abundance, most of them solubilizing inorganic phosphate and promoting the wheat growth. These results suggest that the management of the legume plant cover diversity can optimize the positive impact of legume on the agrosystem productivity resulting from an increase in soil microbial functions, soil microbial diversity, AM symbiosis efficiency in sustainable agricultural practices (crop rotation, intercropping systems, etc). Acknowlegments: This work was funded by the project Fabatropimed supported by Agropolis Foundation under the reference ID 1001-009. (Texte intégral)