Modern intensive agricultural systems generally focus on the productivity of monocultures. They are characterized by a low diversity of crops, with uniform and symmetrical planting layouts. They largely rely on the utilization of chemical inputs. They are widely denounced for their negative environmental impacts. In this context, the ecological intensification framework proposes to use exploit biodiversity in order to better achieve, such ecosystem services and soil conservation. Intercropping, i.e. the simultaneous growth of two or more crops mixed in the same field, appears to have the potentialities to improve the productivity, resilience capacity and ecological sustainability of agrosystems through the intensification of such positive interactions between plants as facilitation and niche complementarity. Cereal-legume intercropping turns out to be effective in low N agrosystems since legumes have the ability to fix atmospheric nitrogen via their symbiosis with rhizobia. This fixed N in turn benefits to the cereal through various ecological processes. The objective of the project is to improve the benefit of legumes for intercropped cereals in low input agrosystems through the management of plant-plant and plant-microbe interactions. The nitrogen fixing symbiosis requires phosphorus and iron to be efficient. While these nutrients are prone to be lacking in N-limited agrosystems as it is the case in Mediterranean agrosystems, plant-plant interactions and plant-microbes (rhizobacteria and mycorrhiza) seem to play an important role for their acquisition, and efficiency in their utilisation. We propose to develop a participatory research project in three Mediterranean agrosystems. Agronomic and environmental diagnosis will be performed on the field to assess N and P biogeochemical cycles as well as Fe availability, in link with the plant performances and the diversity of soil microorganisms. A molecular identification of soil microorganisms from the most productive sites will be done, and a research of genes for tolerance to Fe- and P-deficiencies will be realized. Glasshouse experiments involving various cultivars of cereals and legumes, as well as the beforehand identified microorganisms, will be done in order to disentangle the various mechanisms of nutrient acquisition, sharing and transfer between plants. Other experiments will assessing the effects of cereal-legume-microbe interactions on the development and architecture of the plant root systems and root hair development. These researches are integrated in a strategy of functional ecology on plant-microbe-soil interactions in the low valley of Medjerda at Mateur (Tunisia), Ain Temouchent (Algeria), Haouz (Morocco) and Thessaloniki (Greece). Using multidisciplinary and innovative approaches, the program will provide novel knowledge and understanding of agro-ecosystem management for food production.