Variable rate application (VRA) granular fertilizer spreaders are increasingly important for improved nutrient management of Florida's citrus orchards. Site-specific VRA fertilization based on the canopy size of citrus trees could improve horticultural profitability and fertilizer use efficiency, thereby reducing nitrate leaching. In this study, tree canopy sizes were measured with an ultrasonic sensor system in a 17-ha 'Valencia' orange orchard, and ranged from 0 to 240 m³. Six nitrogen (N) rates (0, 134, 168, 202, 236 and 270 kg ha^-1 y^-1) were applied with a VRA fertilizer spreader according to a prescription map developed from tree canopy size information in one season, and according to real-time canopy sensors in a second season. For comparison, half of the orchard received the standard uniform N rate of 270 kg ha^-1 y^-1. Soil leachate samples were collected with vacuum lysimeters at 1.5-m depth from below the root zones of 36 trees in 18 paired plots. The leachate samples were analyzed for nitrate-N concentration to compare VRA with uniform fertilization treatment. The VRA treatment significantly (p<0.05) decreased nitrate loading from leachates into ground water compared to the uniform treatment. Mean leachate nitrate-N concentrations for all VRA treatments ranged from 1.5 to 4.5 mg L^-1 and were below the maximum contaminant level for groundwater of 10 mg L^-1, while those under uniformly fertilized small and large trees were 28.5 and 14.0 mg L^-1, respectively. Most leaf nutrient concentrations were not significantly influenced by the VRA fertilization and were within the recommended optimal ranges. VRA used 40% less fertilizer than standard uniform fertilization and could improve orchard profitability.