Adjusting Airblast Sprayer Airflow Based on Tree Foliage Density

This paper reports on the development of an electro-mechanical system for exploring the idea of adjusting air output from an airblast sprayer to reduce spray losses from orchard applications. A moving air deflector plate was designed and its horizontal motion was automated by integrating a motion control system consisting of a stepper motor, controller, GPS receiver, laptop computer, and a laser scanner. Foliage density estimates from the laser scanner were used to actuate the mechanical components. Also, two experiments were conducted to evaluate the utility of the system in real-time changing of air output. The first experiment evaluated the role of deflector plate position in modifying air penetration characteristics across trees of different foliage densities. The second experiment consisted of sampling spatial movement of spray droplets with five deflector plate positions. In field trials, the deflector plate moved from the innermost to outermost position (based on foliage density) to change horizontal airflow from 7.6 to 1.9 m3/s, respectively, in 3 s. Various plate settings showed differences in air penetration across tree canopies with various foliage densities. The deflector plate also had an effect on the spatial movements of droplets to some extent. A change of plate setting from innermost (maximum air) to outermost (minimum air) showed about 37% reduction in mean deposition at Far sample location, at high application rate. The results indicate the change in air volume could facilitate reducing off-target spraying in orchard applications.