Performance of a Tower Sprayer with An Electric Variable Air Assist System for Tree Crops

Highlights An experimental tower sprayer with an electrical air assist system (EAAS) was evaluated in an apple orchard and compared to the same sprayer without air assist. Four intensities of air assists, air assist powers of 0% (no air assist), 30%, 50%, and 100% (maximum air assist), were tested for spray depositions and coverages in two consecutive rows, next to the sprayer (spray row) and the adjacent row. Average spray depositions from the sprayer were 5.8, 7.2, 6.4, and 4.8 µL cm-2 in the spray row with 0%, 30%, 50%, and 100% air assist power, respectively. The sprayer with the EAAS at 30% power achieved 24.6% higher depositions in the spray row with similar spray drift on the next row compared to the sprayer without air assist. ABSTRACT. A sprayer for vertical crops with deep canopies requires air assistance to penetrate crop protection product (CPP) into targeted areas. An electrical air assist system (EAAS) was developed with electric fans, air channels, PWM controllers, and a 400-Ah battery to apply variable air assistance to address limitations of conventional air-blast sprayers equipped with axial fans. The performance of a sprayer with the EAAS was evaluated for canopy depositions and coverages on the sprayed row in an apple orchard as the EAAS was operated with 0%, 30%, 50%, and 100% power. In addition, the spray drift potential from each application was evaluated by collecting deposition and coverage from tree canopies in the next row (next to the sprayed row). The results showed that the spray applications with air assistance from the EAAS achieved more uniform average depositions of 4.5 to 7.2 µL cm -2 in the sprayed row, while the application without air assistance had an average deposition of 5.8 µL cm -2 . Moreover, the applications with air assists penetrated spray droplets inside the canopy to attain as much as 83.3% more depositions than the application without air assist. The potential for spray drift was higher from the applications with air assistance from the EAAS, as they had up to 401.4% more depositions in the next row with the maximum air assist. However, spray application with air assistance from 30% powered EAAS had increased spray deposition (24.6%) and similar spray drift potential (~104.0%) compared to the application without air assist. The EAAS would provide a solution to control the outputs of the air assist system to increase inside canopy depositions while reducing spray drift. Keywords: Air-assisted sprayer, Automation, Crop protection, Fan, Pesticide, Pulse width modulation, Spray penetration, Variable air assist.