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The application of pre-emergence, post-emergence, and burn-down herbicides (i.e., glyphosate) continues to increase as producers attempt to reduce both negative environmental impacts from tillage and input costs from labor, machinery and materials. The use of precision agriculture technologies such as automatic boom section control allows producers to reduce off-target application when applying herbicides. While automatic boom section control provides benefits, pressure differences across the spray boom resulting from boom section actuation can lead to off-rate application errors. Off-rate errors may also result from spray rate controller compensation for ground speed changes and velocity variation across the spray boom during turning movements. This project focuses on quantifying accumulated pesticide application for three fields located in Central Kentucky. GPS coordinates were collected along with nozzle pressure data (at 13 nozzle locations) at one second intervals as the sprayer traversed the study fields. The method previously developed by Luck et al. (2009) was used to calculate coverage areas for the control sections along the spray boom in MS Excel. Nozzle discharge flow rates were estimated from the nozzle pressure data (based on manufacturer calibration information) which was then incorporated into MS Excel to determine the rate of pesticide applied to the fields. Results indicate the majority of each field received application rates at or below the target rate. Only 34.2%, 33.9%, and 22.9% of Fields 1, 2, and 4, respectively, received application rates at the target rate +/- 10% during these post-emergence treatments. The goal of this project was develop distribution maps to better understand the effects of boom section control and turning movements on herbicide accumulation.

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.