Location: Application Technology Research2011 Annual Report
1a. Objectives (from AD-416)
To develop two advanced and affordable spray systems that employ intelligent technologies to continuously match system operating parameters to crop characteristics, insect/disease pressures and microclimatic conditions during pesticide applications.
1b. Approach (from AD-416)
Will develop two intelligent expert precision spraying systems implementing five main components to apply the amount of pesticides as needed. The first system will be an air-assisted variable-rate sprayer to be used for shade, flowering and ornamental trees in nurseries. The second system will be a hydraulic boom variable-rate sprayer to be used for flowering container plants in greenhouses and woody ornamentals in nurseries. Due to the similarity of crop structures, the use of the first system can be expanded to other specialty crops such as fruit trees and vineyards, and the second system can be expanded to berries and vegetables. The five components will be: a sensor-controlled unit to control spray outputs that match structures of specific floral and nursery crops, an expert subsystem to assist choosing proper chemicals and application schedules, a direct in-line injection unit to inject concentrated chemicals to individual nozzles to eliminate leftover disposals, a off-target recovery unit to prevent spray off-target losses including drift beyond target areas, and a fluid delivery subsystem to discharge spray outputs with variable rates. All the operations will occur as the sprayer moves past the canopy, providing uniform spray coverage of the canopy with minimum pesticide use and off-target loss beyond the target area. Speciality Crops Research Initiative.
3. Progress Report
An experimental real-time variable-rate sprayer that implemented high frequency ultrasonic sensors and pulse width modulation solenoid valve-controlled spray nozzles was developed to adjust spray outputs automatically based on the liner canopy size. The accuracy of the sprayer in triggering spray against detected targets was evaluated by use of a high-speed camera. A laboratory field consisting of six different sized tree species was used to test the sprayer performance consistency. Influences of liner canopy size and sprayer travel speed on uniformity of spray deposition and coverage inside nursery liner canopies were analyzed. An intelligent air-assisted sprayer implementing a high speed laser scanning sensor 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 solenoid valve to achieve variable rates based on the occurrence and canopy characteristics of the target, such as height, width and foliage density. 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. The intelligent air-assisted sprayer with variable flow rate of individual nozzles was tested for ornamental nurseries and fruit trees. The accuracy of the sprayer to maintain constant droplet size distributions and constant operating pressure was evaluated under both laboratory and field conditions. 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. This research addressed critical elements for the development of precision sprayer technology envisioned in 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”.