Performance of an ultrasonic tree volume measurement system in commercial citrus groves

Florida growers have planted citrus groves at varying spacings to improve resource efficiency and to optimize fruit production for maximum economic return. Four commercial groves with different row spacings and tree ages were scanned with a Durand-Wayland ultrasonic system to measure and map tree volumes and to examine the effect of row spacings and tree ages on ultrasonic measurements. The ultrasonically measured volumes (UVs) were compared with manually measured tree volumes (MVs) of 30 trees in each grove to examine the performance of the ultrasonic system. The ultrasonic system measured tree volumes reliably in different groves with an average prediction accuracy (APA) >90%, and correlation with manual measurement of R2=0.95-0.99. Standard error of prediction and root mean square errors were relatively higher in widely spaced old groves than closely spaced young groves. The ultrasonically sensed tree volume map showed substantial variation in canopy volumes (0-240 m3 tree-1) within the grove. Therefore, the use of ultrasonic systems is a better option to quantify and map each tree volume rapidly (real-time) for planning site-specific management practices accurately in commercial groves and for estimating fruit yield. © 2005 Springer Science+Business Media, Inc.