In order to better predict the performances of legume-based intercrops, it is necessary to increase our knowledge on the onset of the competition between mixed species. Thus, early growth, from emergence to the beginning of competition, is a key step in determining initial competitive ability of each species. Early growth would depend on seed and seedling traits, i. e. seed mass, emergence (epigeal or hypogeal) in relation with sowing conditions, i. e. duration of emergence, nutrient availability. The objectives of this thesis were (i) to identify and model the effects of key factors impacting on early growth in relation with seed and seedling traits and sowing conditions (ii) and to assess the impacts of early growth variations on subsequent growth. Carried out experiments enabled analysing and modelling the effects of seed mass and of the degree of the emptying of seminal reserves (in relation with the duration of emergence) on early growth. Mineral nutrition had a stimulating effect for all studied species. The integration of early growth in a model simulating the functioning of a pea-wheat intercrop (AZODYN-IC) showed that variations in early growth impacted on the biomass and the proportion of each species at the end of the cycle. These impacts were also observed experimentally. Obtained results provide evidence to predict the functioning of intercrops and to propose technics to manage the performances of such systems.
