Regulating Airflow of Orchard Airblast Sprayer Based on Tree Foliage Density

Adjustment of orchard sprayer air output, using an electro-mechanical system, was investigated for reducing spray losses. This system automated horizontal movement of an air deflector plate inside the sprayer air outlet by using foliage density signals from a laser scanner. A field test was conducted to evaluate the role of the deflector plate position in modifying air penetration through tree canopies of different foliage densities. Another test involved sampling horizontal movement of spray droplets, in an open area within a citrus orchard, at different deflector plate positions. The deflector plate could move from the innermost to the outermost position (to change horizontal airflow from 7.6 to 1.9 m3 s-1) in about 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 movement of droplets to some extent. The results suggest that limiting the sprayer airflow to the canopy depth may potentially reduce spray losses from orchard applications.