Given the difficulty to determine N status in soil testing and lack of crop parameters to recommend N for sugarcane in Brazil raise the necessity of identify new methods to find crop requirement to improve the N use efficiency. Crop canopy sensor, such as those used to measure indirectly chlorophyll content as N status indicator, can be used to monitor crop nutritional demand. The objective of this experiment was to assess the nutritional status of the sugarcane fertilized with different nitrogen rates applied at different periods after harvest, through diagnostic sensors in order to determine the parameters for sustainable application of N-fertilizer in sugarcane. This experiment was conducted during two seasons (2013-2014 and 2014-2015) and the experimental design was a randomized block with split plot with four replications. The plots were divided into different application periods of N fertilizer after the sugarcane harvest (0, 30, 60, 90, and 120 days after the harvest - DAH), and the split plots in five rates of nitrogen (0, 50, 100, 150 and 200 kg ha^-1N). During the experimental period (30, 60, 90, 120 and 150 DAH), the biometric measurement was performed to evaluate the aboveground performance (number of tillers/stalks, and the number of green and dry leaves, into the split plots). The crop N status was evaluated through vegetation index (NDVI and NDRE) readings using a crop canopy reflectance sensor (ACS 430 Crop Circle – Holland Scientific). The N-fertilizer application period as well as, the rate of nitrogen applied to the ratoon, influenced the sugarcane yield. In the first crop season, the best N rate was 140 kg ha^-1, applied at 0 or 60 DAH. In the second year, the best N rate to improve sugarcane yield was 100 kg ha^-1 N, applied at 0 or 30 DAH. Crop Circle sensor was better correlated with the application periods and N rates during crop development, with good correlations with yield when the evaluations were done at 90 and 150 DAH. NDVI reading had a good correlation with the applications periods of N fertilizer and NDRE was more sensitive to N rates. The best time to use the crop canopy reflectance sensor is associated with lack of water stress. Crop Circle sensor can be considered an auxiliary tool to predict the real need of N fertilizer in sugarcane.