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Citrus is the most important agricultural crop in Florida. Heavy reliance on agricultural chemicals and low efficiency of fertilizers have raised many environmental and economic concerns. In this study, a nitrogen sensing system for citrus leaf will be developed. Based on chlorophyll and protein absorbance bands, the sensing system will cover wavelength ranges of 620-950 nm and 1400-2450 nm. A reflectance housing was designed to block environmental noise and to ensure single leaf measurement. A halogen light source, two detector arrays, linear variable filters and a data acquisition board with 16-bit ADC were used. The designed system has no moving parts, so it is robust and resistant to vibration. The system will be tested in a laboratory and in commercial citrus groves. An algorithm will be developed to assess nitrogen status according to analysis results of previously collected data set. Some basic test results of the sensor showed that the system provided nitrogen information from the obtained spectrum. However, more tests are needed in the near future to improve the performance of the sensing system.