Performance of a tower sprayer with an electronic variable air assist system for tree crops

Authors: Jeon, Hongyoung; Zhu, Heping

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2025
Publication Date: 5/1/2025
Citation: Jeon, H., Zhu, H. 2025. Performance of a tower sprayer with an electronic variable air assist system for tree crops. Journal of the ASABE. 68(2):321-333. https://doi.org/10.13031/ja.16004.
DOI: https://doi.org/10.13031/ja.16004

Interpretive Summary: Safeguarding specialty crops from insects and diseases often requires application of crop protection products (CPP). Spray application is the most common method to deliver CPP to specialty crops. Because of thick canopies common to many specialty crops, CPP sprays are often accompanied by air assist to deliver and penetrate the canopies for effective pesticide coverage. Typical air assist systems for specialty crop sprayers are oversized to ensure coverage over a broad variety of crops, and often provide excessive air assist. A prototype electric variable air assist system for new tower sprayers was developed to address such issues by providing optimized air assist with spray. Optimized air assist could be achieved by changing speeds of electric fans from an onboard computer program in real time. A sprayer with the system was tested for its performance with increasing spray depositions and reducing spray drift in an apple orchard. The results showed the system increased spray canopy deposition by approximately 50% and reduced spray drift by approximately 74% compared to a conventional sprayer. The research outcomes can be used to develop a new electric air assist system for sprayers to optimize CPP applications with delicate control of air assist intensities. The system will reduce fossil fuel use for CPP applications and minimize spray drift to reduce negative environmental impacts.

Technical 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 channel, PWM controllers and a 400-Ah battery to apply variable air assist to address limitations of conventional air-blast sprayers equipped with axial-fans. The performance of a sprayer with EAAS was evaluated for canopy depositions and coverages on the sprayed row in an apple orchard as EAAS was operated with 0%, 30%, 50% and 100% power. In addition, the potential of spray drift 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 assist from EAAS achieved more uniform average depositions of 4.5 to 7.2 µL cm-2 in the sprayed row while the application without air assist had average deposition of 5.8 µL cm-2. Moreover, the applications with air assists penetrated spray droplets inside canopy to attain as much as 83.3% more depositions than the application without air assist. The potential of spray drift was higher from the applications with air assist from EAAS as they had up to 401.4% more depositions in the next row with the maximum air assist. However, spray application with air assist from 30% powered EAAS had increased spray deposition (24.6%) and similar spray drift potential (~104.0%) compared to the application without air assist. EAAS would provide a solution to control the outputs of air assist system to increase inside canopy depositions while reducing spray drift.