ARS | Publication request: A Real-time Variable-Rate Sprayer for Nursery Liner Applications

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 20, 2010
Publication Date: June 23, 2010
Citation: Jeon, H.Y., Zhu, H., Derksen, R.C., Ozkan, H.E., Krause, C.R. 2010. A Real-time Variable-Rate Sprayer for Nursery Liner Applications. American Society of Agricultural and Biological Engineers International Meeting, June 20-23, 2010, Pittsburgh, Pennsylvania. ASABE Paper #1008801.

Technical Abstract: The use of conventional sprayers for control of pests and diseases with pesticides is excessive for ornamental nursery tree liner applications. A real-time variable-rate experimental sprayer was developed to reduce pesticide usage by coinciding spray outputs with canopy sizes. The sprayer consisted of two parallel vertical booms, an ultrasonic sensing system, a solenoid-activated spray output modulation system, a microprocessor-based controller and a spray delivery system. The two booms incorporated five opposing pairs of equally spaced variable-rate nozzles. Target trees were encompassed centrally by the booms and were sprayed by the opposing pairs of nozzles. The total amount of sprays delivered from all active nozzles was based on the tree size, and a particular pair of nozzle was triggered by the exposed canopy surface. The sprayer performance, which included accuracy of spray timing and spray modulation, and percent spray coverage inside tree canopies, was evaluated at a travel speed of 3.2 km/h. The accuracy of spray timing was validated with a 5-ms resolution, high-speed digital camera, and the accuracy of spray modulation with an oscilloscope. Water sensitive papers (WSP) placed inside the conifer canopy were used to evaluate spray coverage. Test results showed that the paired nozzles were triggered at 4.5 to 12.5 cm in advance of the canopy. For every 100 ms, the sprayer modulated a spray volume of 1.5 to 2.6 mL at distances of 0.30 to 0.76 m from the sensor to the canopy. The experimental sprayer applied 111.1 to 222.3 L/ha from a pair of nozzles to the sensor-coupled target area. Compared with conventional constant rate (935 L/ha) sprayers that are used in this application, the experimental sprayer reduced the average application rates by 59 to 75 %. Spray coverage areas on WSPs for the constant and variable rate applications ranged from 1.8 to 34.7 % and 1.9 to 41.1 %, respectively. These tests confirmed that reduced pesticide usage could be achieved when variable-rate spray applications are coupled with canopy size.