ESTIMATION OF CITRUS FRUIT YIELD USING ULTRASONICALLY-SENSED TREE SIZE

Abstract

Tree canopy mapping with an automated ultrasonic system is inexpensive, fairly straightforward and could be usedto estimate fruit yield within a grove to plan site-specific management practices. Tree canopy volumes and fruit yield weremeasured and mapped in a 17.0-ha Valencia grove with an automated ultrasonic system and a sensor-based automatic yieldmonitoring system, respectively. The spatial data were divided into 40 equal sized plots using ArcView GIS software to relatetree sizes and fruit yield.<br><br>A linear calibration model with half the data showed that ultrasonically-sensed tree sizes correlated significantly (R2 =0.80) with fruit yield. The correlation between actual and predicted fruit yield with the remaining data was used for validationand was also significant (R2 = 0.42). The average prediction accuracy was 90.6% while the standard error of prediction androot mean square error were 4.25 and 4.16 Mg/ha, respectively. The ultrasonically-sensed tree canopy volumes of plots rangedfrom 7421 to 20,900 m3/ha;fruit yield within the grove was also variable, ranging from 21 to 45 Mg/ha. Tree size and yieldmaps produced similar spatial patterns within the grove, as high-yielding areas were associated with large tree canopies.Therefore, tree canopy size could be used to estimate fruit yield within the grove. This information is valuable to forecastyields, to plan harvest schedules and to generate prescription maps for site-specific management practices on an individualtree basis.