Interseeding cover crops in grain corn offer an opportunity to improve the sustainability and long –term productivity of corn production systems in cool humid regions of Canada. The objectives of this study were to investigate the effect of cover crops species, N fertilizer rate and AMF (G. irregulare) inoculation on corn biomass and N uptake. Cover crop treatments include red clover, microclover, hairy vetch, bush bean and control (no cover crop). Soil was pasteurized at 80°C for 40 minutes before planting. Rectangular pots (66 cm length*24 cm width) filled with field soil were used in the greenhouse (24-27°C, 16 h daylight). Two N fertilizer rates (10 and 80 kg N ha^-1) were applied. Pots were inoculated by AMF or were not inoculated. Corn and legume aboveground dry biomass were measured 7 weeks after seeding. Results indicated cover crop species and fertilizer N rates were the main factor that influenced corn dry biomass. Within cover crop treatments, lower corn biomass were measured in bean (46.87g pot^-1) and in vetch (54.69 g pot^-1) compared with control (92.76 g pot^-1). No significant differences were found between the two clover species and control. Bean and vetch dry biomass were 7.1 and 3.0 times higher than the red clover biomass (6.08 g pot^-1). High N rate negatively (p≤0.05) impacted the biomass of all legume cover crops except hairy vetch. Overall, competition between cover crops and corn were the main factor that affected corn biomass. Delaying cover crop seeding, and using less aggressive and shade tolerant cover crops species are recommended. The plant N uptake data will be presented.