Globally, the agricultural nitrogen use efficiency (NUE) is no more than 40 %. This low efficiency comes with an agronomic, economic and environmental cost. By better management of spatial and temporal variability of crop nitrogen need, NUE can be improved. Currently available crop canopy sensors based on reflectance are capable of detecting N-deficiency in corn, but only during or after the maximum nitrogen uptake period (maize crop growth stages of V8 to V16). Our hypothesis is that other optical signals such as UV-induced fluorescence have the potential to detect N-deficiency before the onset of maximum nitrogen uptake period in maize crop (prior to V6-maize crop growth stage). To test this hypothesis, a UV-induced fluorescence sensor (Multiplex, Force-A, Orsay France) was used. This study was conducted in a greenhouse on maize plants. Four rates of N-fertilizer were tested, notably: 0 kg/ha, 75 kg/ha, 150 kg/ha and 225 kg/ha equivalent on maize plants. Our preliminary data analysis indicates that nitrogen balance index (NBI) obtained from Multiplex sensor successfully detected / differentiated N rates as early as maize crop growth stage of V5. Detailed results will be presented at the conference.