The objective of this on-farm study was to determine the effects of corn planting population on forage yield, plant phosphorus (P) concentration, and P removal from the soil. The study was performed during the spring and summer seasons of 2014 and 2015 at 2 commercial dairy farms located in Virginia. The study included 7 cornfields with different growing and harvesting conditions. In each cornfield, corn was planted in plots at a theoretical seeding rate of 55,000, 70,000, 85,000, and 100,000 seeds/ha (55K, 70K, 85K, and 100K, respectively). Each seeding rate had 4 replicates within each cornfield. Corn was planted with no-till planters. For all cornfields, the preceding crop was annual ryegrass that was harvested for silage within 10 d before planting corn. Fertilization was the same for all plots and followed nutrient management plans of each farm. At harvesting time, 10 plants from each plot were cut by hand (15 cm above ground), weighed, chopped, mixed, and analyzed for DM and P concentrations. All variables were analyzed using the MIXED procedure of SAS. The statistical model included the effects of field (fixed; 6 df), planting density (fixed; 3 df), planting density nested within field (fixed; 18 df), and the random residual error. Plant DM biomass decreased linearly when planting density increased (376 vs. 253 g of DM/plant for 55K and 100K, respectively; P < 0.01), whereas DM yield increased linearly when planting density increased (19.8 vs. 26.0 Mg/ha for 55K and 100K, respectively; P < 0.01). The concentration of P in the fresh forage was highest (P < 0.01) for 55K and 70K (0.250% DM) and lowest for 85K and 100K (0.235% DM). The removal of P through the harvested biomass increased linearly (P < 0.01) when increasing corn planting density (14.0, 16.8, 19.2, and 23.2 kg P/ha for 55K, 70K, 85K, and 100K, respectively). In conclusion, increasing corn planting density decreased P concentration in the corn plant and increased P removal from the field.