EFFECTS OF FOLIAGE DENSITY AND GROUND SPEED ON ULTRASONIC MEASUREMENT OF CITRUS TREE VOLUME

Abstract

Ultrasonic sensors can be used to quantify and map tree canopy volume, which is useful for planning site-specificmanagement practices within a grove and estimating crop yield. An experiment was conducted to examine the effects of thecanopy foliage density and ground speed on the performance of the Durand-Wayland ultrasonic system in tree volumemeasurement. Fifteen densely foliated (dense) and 15 partially defoliated (light) citrus trees were scanned from both sidesat three ground speeds in three replications. The measurements were compared to those calculated from manual measurementsof the tree dimensions. The difference between ultrasonic and manual volumes was used to evaluate the performance of theultrasonic system.<br><br>The difference between ultrasonic and manual volumes ranged from 17.3% to 28.71% at the 95% confidence level. Ninetyfive percent of the ultrasonic measurements were repeatable within 12.7% to 30.9% of the manual volume. Canopy foliagedensity had significant effect on ultrasonic measurements of canopy volume. The volume difference was higher in light thandense trees. There was no significant effect of ground speed (1.6 to 4.7 km/h) on ultrasonic volume measurements. Variabilityof the measurements in partially defoliated canopies increased as ground speed increased. There was a significant differencebetween the volumes of two sides of the trees.