Through their root systems, plants are soil engineers capable of altering the biological, chemical and physical properties of the soil they colonize. However, while soil properties are generally studied and considered for their impact on plant processes (nutrient / water uptake, growth and yield), the fact that, conversely, the plant acts on soil properties through its root system, and its feedback to the plant, is much less investigated. Many of these soil-plant interactions take place in the rhizosphere, the tenuous zone of soil surrounding the roots impacted by their activity. This zone is a 'hotspot' of biological activity supported by the supply of root derived carbon (rhizodeposition), comprising specific polymeric compounds (in particular exopolysacharides, EPSac). We argue here that the root/rhizosphere effect on the soil is a lever for acting on crop tolerance to water deficit, using a few examples from our recent works. We also showed that some plant rhizospheric traits (e.g. rhizosphere size, microbial catabolic biomass/profiles, rhizodepot quantity/composition, water retention, soil aggregation) vary according to crop species and genotype. These initial results suggest the potential value of studying these rhizospheric processes in an agroecological context of plant diversification.

More generally, in the context of diversification of cropping systems and rotations, root systems could be a tool for managing the hydraulic properties of the soil to optimize the water balance at plot level (runoff/infiltration sharing, water storage, drainage and groundwater recharge).