2011 Annual Report
1a.Objectives (from AD-416)
Objective 1: Investigate how droplet impact, retention, and evaporation are affected by target surface characteristics and pesticide formulation physical properties and establish a complex pesticide transfer function from fundamental research to new precision sprayer development.
Objective 2: Develop computer control systems for laser-guided precision sprayers to accommodate various tree canopy characteristics.
1b.Approach (from AD-416)
In cooperation with the ARS Application Technology Research Unit, Wooster, OH, perform the following: (1) determine evaporation time, spread factor and chemical residual pattern formation of droplets containing spray additives on horticultural leaves via sequential imaging under controlled conditions; (2) investigate influences of droplet size and velocity, spray formulation, and morphological surface of leaves on spray droplet impaction, retention and coverage to develop strategies for enhancing delivery to target areas; and (3) develop a precision air-assisted sprayer with multi-jet nozzles to reduce the amount of pesticides required by matching spray characteristics to specific types of nursery and fruit trees. A fast response, high resolution controller will be developed to control air velocity, spray application rate and number of jets required for each air jet nozzle. All these operations will occur as the sprayer moves past the tree, providing uniform spray coverage of the tree with minimum off-target loss beyond the tree row.
An intelligent air-assisted sprayer implementing a high speed laser scanning sensor (LIDAR) was developed to vary spray output of each individual nozzle to match target tree needs in real time. Each nozzle was coupled with a pulse width modulation (PWM) solenoid valve to achieve variable rates based on the occurrence and canopy characteristics of the target, such as height, width and foliage density as determined by LIDAR. A unique density algorithm was developed to calculate foliage density by mapping the surface roughness of the canopy during the spray application. A back pressure control unit was integrated into the system to minimize the pressure fluctuation due to frequent changes in nozzle flow rates. Delay time between the sensor detection of the canopy and the nozzle activation was determined with a high-speed video camera. Laboratory tests demonstrated that the design criteria of the experimental sprayer were acceptable for performing variable rate functions.
The intelligent air-assisted sprayer with variable flow rate of individual nozzles was tested for ornamental nurseries and fruit trees. The sprayer was developed with a conventional air-assisted orchard sprayer by implementing a laser scanner to detect canopy characteristics, five-port air-assisted nozzles coupled with pulse width modulation (PWM) solenoid valves, and an automatic flow rate controller to minimize pressure fluctuation. Spray performances were compared for the new sprayer with the same sprayer without the intelligent control and a conventional air blast sprayer in an orchard at three different growing stages. Measurements were made for spray deposition and coverage inside canopies, losses on the ground and beyond target trees, and airborne drift downwind from the target trees. Compared to conventional sprayers, the variable-rate sprayer produced relatively uniform spray coverage and deposition inside canopies, and reduced spray volume by 47% to 73% with significantly less off-target losses on the ground, through gaps between trees, and in the air.
This research addressed critical elements for the development of precision sprayer technology envisioned in the ARS parent project Objective 1 “Develop precision sprayers that can continuously match canopy characteristics to deliver agrichemicals and bio-products accurately to nursery and fruit crops”.
Cooperator’s Designated Representatives directly worked with the Authorized departmental officer's designated representative to plan and execute the project. They met daily to discuss the project progress.