UAV ELECTROSTATIC SPRAY DEPOSITION ON APPLE TREES: A STUDY ON DROPLET DISTRIBUTION DURING BLOOMING STAGE

Abstract

This study investigates the effect of electrostatics in UAV spraying to enhance droplet deposition efficiency during the blooming stage of apple trees. Experiments were conducted under two operating conditions - electrostatic spraying and non-electrostatic (conventional) spraying - at UAV flight heights of 1.0 m, 2.0 m, and 3.0 m above the apple tree canopy. Spray deposition was measured by placing test paper on the upper, middle, and lower canopy layers, on both the front and the back sides of the leaves. The results show that, compared with conventional UAV spraying, electrostatic force increased droplet number density by 17.6% and reduced droplet size by 25.3%, thereby improving overall spray performance. This provides notable advantages for pollination and pest control during the early growth stage of apple trees. The electrostatic charge generates an attractive force between charged droplets and the target surface, enhancing droplet adhesion and deposition on the back side surfaces of lower leaves and flowers. However, this advantage is not significant on the back sides of upper and middle canopy leaves due to limited recirculating airflow reaching those locations. These findings support the application of electrostatic technology to improve pollination efficiency and precision pesticide spraying during the early developmental stage of apple trees.