Field experiments were conducted in the Dominican Republic to determine the effects of nitrogen (N) supply and purple nutsedge population densities on the yield of radish. An additive series of 0, 50, 100, 150 and 200 purple nutsedge plants per m2 was established the same day radish was sown. Nitrogen rates were 100 and 200 Kg/ha. Marketable radish yield losses, and purple nutsedge shoot dry weight and height were determined 30 days after seeding the crop. Nutsedge densities and Ν rates independently affected radish root yield, but no significant Ν by density interaction was detected. Root yield loss reached 100% at nutsedge densities of 75 and 125 plants per m2 at 200 and 100 Kg N/ha, respectively. Purple nutsedge produced larger shoot biomass as Ν increased from 100 to 200 Kg/ha. No significant differences were observed for purple nutsedge height, regardless of the Ν rate utilized. Results show that as Ν increased the negative effect of the weed on the crop was enhanced.