In most crop rotations that include corn, nitrogen (N) applied to the corn phase is a proven and profitable practice. Corn in some rotations requires little to no N input, with first-year corn following established alfalfa as an example. Corn in other rotations requires substantial N input to meet plant requirements, with continuous corn (CC) typically requiring the greatest input. Other rotations or corn phases will be intermediate in N application requirement. With corn in the two most common crop sequences in the Corn Belt, corn following soybean (SC) and CC, if N is not applied, then yield will suffer. If N is not applied on an on-going basis, then over time corn yield will often average around 50 to 60 bu ac-1 in CC and 100 to 110 bu ac-1 in SC, or less. Consequently, the soil system typically cannot supply the full corn plant N requirement. On average, the yield with no N applied is around 70% in a SC rotation and 55% in CC of the yield obtained at an economic optimum rate. Therefore, supplemental N is needed to reach economic yield potential.