Due to lower and less regular yields and in spite of numerous advantages (N fixation, protein content in the plant, cereal diseases and pest limitation, …), grain legumes are rarely cropped in Walloon area. Nevertheless, in low inputs farming systems they play, based on their symbiotic N2 fixation proprieties, a key role to sustain soil fertility (Bedoussac et al. 2015). In this context, in order to counter poor competitiveness of legumes against weeds, to limit pest and diseases development and/or to limit lodging risks, peas are often associated to cereals in intercropping schemes. Now, it is difficult to reach an interesting pea density in the harvested mixture, not to high, in order to limit lodging risks, especially with fodder pea, and not to low, in order to have a real added value and contribution of the legume to N delivery to the system. In order to modulate final pea content in the mixture and global yield, we propose to test the impact of three different pea sowing densities, both for protein pea and fodder pea, and of three different levels of fertilization at the end of winter.