Commercial variable rate technology (VRT) fertilizer spreaders for citrus are currently being implemented inFlorida groves to improve profitability and reduce nitrate contamination of groundwater. Although VRT spreadersincorporate proven embedded controllers and tree sensors which permit changing fertilizer rates according to tree size, thereis currently limited information on their performance characteristics in spatially variable groves. This study investigated theperformance characteristics of a split-chain, spinner-type VRT spreader during fertilization of a commercial citrus grove.Six nitrogen rates (0, 134, 168, 202, 236, and 270 kg ha-1 y-1) were varied according to a prescription map developed fromultrasonically measured tree size information. Missing trees and one-year-old reset trees were not fertilized with the spreader.Target fertilizer rates for 1490 trees in an 8.1-ha experimental area were compared with actual fertilizer rates calculated fromgeartooth speed sensors monitoring the conveyor chain speed. Through classification and regression analysis, spreaderperformance and response times during transitions from zero or low fertilizer rates to high rates and vice versa werecompared. In this grove, 73.1% of the fertilizer rate changes were required between a single-tree space of 5.3-m linear rowdistance, taking about 4 s to drive at 1.34 m s-1. The spreader had an average on-off response time of . 3 s, and an averagerate changing response time of 2 to 5 s. Based on these data, the spreader design is not suitable for rapid fertilizer rate changesbetween single tree spaces, but could be greatly improved by substituting its hydraulic servo control valves with faster devices.