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Nozzle Uniformity for Agricultural Sprayers Operating Under Field Operation when Using Automatic Section Technology

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1009386.(doi:10.13031/2013.35728)
Authors:   Ajay Sharda, Joe D Luck, John P Fulton, Scott A Shearer, Timothy P McDonald
Keywords:   Liquid application, precision agriculture, distribution, pressure, variable-rate technology, as-applied maps

The adoption of automatic section control technology is increasing since it reduces application overlap and application in unwanted areas leading to input savings and improved environmental stewardship. Spray controllers attempt to maintain the desired target application rate when implementing auto-section control but concerns exist about whether intended nozzle flow rates are sustained at all times. Therefore, a study was conducted to evaluate nozzle flow rate and control system response in maintaining target application rates during field operation. Specific objectives were to: 1) map real-time nozzle uniformity CV (%) during field operation and 2) quantify the difference between target and actual nozzle (% off-rate) flow rate. Field experiments were conducted using common self-propelled sprayers equipped with commercially available controller systems with automatic section control and guidance capabilities. High frequency pressure sensors were mounted across the spray boom to record nozzle pressure with data stamped with GPS locations. Nozzle pressure were converted to nozzle flow rate using manufacturers calibration curves and nozzle CV, off-rate and flow rate settling times were calculated. Results indicated that target application rate changed frequently with ASC engagement and ground speed changes on irregular field boundaries with no-spray zones. The nozzle off-rate beyond 10% occurred for approximately 60% and nozzle uniformity CVs for 25% of the time when operating in irregular shaped fields using auto-nozzle control sprayer. Static experiments during ASC engagement and sprayer acceleration and deceleration demonstrated that nozzle off-rate can vary from -27.6% to 37.2%, thus complimenting the field results. Auto-boom and auto-nozzle control sprayers results indicated that ASC engagement plus sprayer acceleration will result in under-application whereas ASC engagement and deceleration will over-application. Nozzle flow stabilization time up to 20.0 s during ASC engagement and/or speed change was irrationally high and needs to be investigated further. Overall, irregular fields can amplify application errors though extent and magnitude may vary with selection of type of section control strategy selected (boom or nozzle control), control algorithms, and controller response.

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