Organic grain system managers have to find solutions to nitrogen deficiency and weed infestation. It is especially true when no animals are present on the farm to justify the use of forage legumes despite their interests in the crop succession. Our study focused on the role of four legume cover crop species inserted in a succession of winter wheat and maize on both problems. This insertion consisted in relay-intercropping the legumes under the canopy of wheat. Cover crops were maintained on the field after the harvest of the cereal until the sowing of the subsequent maize crop. The performance of the three crops of the succession was monitored as well as weed development and nitrogen dynamic in the soil-plant system. On the one hand, our results showed that black medic and red clover, that supported the best the competition of wheat, were likely to decrease its grain protein content at harvest (-0.3 to -0.4 %). On the other hand, the four species did not decrease intercropped wheat grain yield. They were able to control weed infestation during the intercropping period and between the two cash crops. Finally, nitrogen restitution to the subsequent maize crop was efficient and allowed a significant 30 % increase of maize grain yield
