Among all plant nutrients used in agriculture, nitrogen (N) is the least efficient mainly due to its mobility in the soil. The possibility of real-time sensing to detect variability in N deficiency within a field would enable variable rate application of inputs and potentially reduce crop production costs and environmental risks. The objective of this study was to evaluate if fluorescence and reflectance sensors can detect variability nitrogen levels in crop canopy at early growth stages of corn (prior to V8). The experiment was conducted in two corn fields to evaluate the reflectance based normalized difference vegetation index (NDVI) and the fluorescence based nitrogen balance index (NBI) in experimental plots which received different N rates. Sensor readings were analyzed using ANOVA to detect differences among N rates. Preliminary analysis suggests that crop canopy sensors can detect nitrogen variability as early as V4 growth stage in corn.