Nitrogen nutrition of grain legumes in the present French agriculture; the example of soybean

abonos nitrogenados azote besoin nutritionnel bradyrhizobium conduite de la culture crop management fertilisation fertilizer application fixation de l'azote glycine max inoculation inoculation methods manejo del cultivo necesidades de nutrientes nitrogen nitrogen fertilizers nitrogen fixation nudosidades radiculares nutritional requirements oil crops plantas oleaginosas root nodules rotation culturale rotational cropping