A better understanding of how plant growth, N nutrition and symbiotic nitrogen fixation (SNF) are influenced by soil inorganic N availability, for a wide range of legume species, is crucial to optimise legume productivity, N2 fixation, while limiting environmental risks such as N leaching. A comparative analysis was performed for ten legume crops, grown in a field experiment and supplied with four levels of N fertiliser. Dry matter, N concentration and SNF were measured. Parallely, root traits were studied in a greenhouse experiment. For most species, inorganic N inputs had little effect on plant growth and N nutrition. SNF was negatively affected by soil inorganic N available at sowing but with large differences among species. The response varied according to plant N requirements for growth and plant inorganic N uptake ability. Legumes root systems differed according to root exploration of the soil, root branching and their response to inorganic N inputs; these observations were in great accordance with observations of plant ability to uptake inorganic N measured in the field experiment. Combining SNF response to soil inorganic N, shoot N and plant ability to uptake inorganic N, allowed a robust evaluation of species differential response to soil inorganic N.