Active crop canopy reflectance sensors can be used during a sidedress N application to modify on-the-go fertilizer rates; but will this method be an improvement to current approaches for developing N recommendations? Our objective was to compare the potential for developing N recommendations for corn (Zea mays L.) based on an active sensor with those developed from more traditional approaches. Corn was grown at four sites in each of two years. Pre-plant whole-plot treatments included a control, 56 kg ha^-1 N as NH₄NO₃, and 129-185 kg ha^-1 available N as manure. Split-plot treatments included six N rates applied at the 6-leaf growth stage (0, 22, 45, 90, 135, 180, and 280 kg ha^-1) and one pre-plant N rate (280 kg ha^-1) as NH₄NO₃. Canopy reflectance in the 590nm and 880nm wavelengths and SPAD measurements were collected at the 6-leaf growth stage. Relative Green Normalized Difference Vegetation Index (RGNDVI) was determined for each whole plot, as GNDVI₀ / GNDVI₂₈₀. Economic Optimum N Rate (EONR) was determined using a quadratic-plateau yield response function. When 56 kg ha^-1 N was applied at planting EONR was not related to RGNDVI; however, when N fertilizer was not applied or when manure was applied at planting, EONR was strongly related (r²=0.79) to RGNDVI in a linear-floor type relationship. Nitrogen recommendations for each whole plot treatment deviated from EONR by: i) -68 to 126 kg ha^-1 N when determined from a soil testing lab; ii) -49 to 162 kg ha^-1 N when based on the Pre-Sidedress N test; and iii) -139 to 115 kg ha^-1 N when based on a SPAD meter. Economic optimum N rate was strongly related to RGNDVI, when commercial fertilizer was not applied at planting, and offers the potential to improve N recommendations for corn.