Farm managers use highly productive and mechanized agricultural sprayers to efficiently cover cropland. These sprayers use modern control systems including automatic section control (ASC) capabilities to manage target application rates. These “precision” technologies typically provide many benefits to users but also have limitations. Therefore, this study was conducted to evaluate spray boom dynamics during rate control system response on agricultural sprayers. A methodology was established to evaluate boom flow dynamics for agricultural sprayers using rate control systems equipped with ASC technology. Field tests with a John Deere 4930 (36.6 m spray width) having auto-boom capabilities and an AG-Chem Rogator SS 1074 (30.4 m) with auto-nozzle control were conducted to assess nozzle uniformity and accuracy during field operation. Additionally, a Schaben 18.3 m sprayer was selected for conducting static tests. Individual boom- and nozzle-section(s) were turned OFF and then back ON when using flow and no-compensation. Tests were also conducted by simulating a sprayer moving OUT and then back INTO point rows at different angles. Further, two different flow control configurations were evaluated involving 2-way and metered 3-way boom shut-off valves to study the impact of control hardware on nozzle flow performance during ASC actuation. Finally, the impact of control components response tuning on nozzle flow stabilization was studied using different flow regulating valves.

Nozzle off-rate was beyond ± 10% of the target rate for both rectangular and irregular fields. Nozzle off-rate occurred for a greater percentage (65%) of time in irregular shape fields primarily due to frequent ground speed changes and ASC actuation. Overall, the control system response resulted in greater under-application (49%) than over-application (17%) during field tests. Static tests involving ASC actuation and ground speed variations supported field results. Nozzle pressure and corresponding flow deviated between 4 and 18% from target rates when boom-section(s) were turned OFF and back ON. Nozzle flow was always higher (4 to 18%) and exhibited long settling times (up to 25 s) as compared to the overall system flow. The difference in pressure increase was statistically different between auto-boom and auto-nozzle control and also for compensation and no-compensation. Control system response resulted in over-application (up to 11%) when moving OUT and under-application (up to -37%) when moving back INTO point rows. Nozzle flow was beyond ±5% the target rate (off-rate) for up to 19 s. The control system was able to maintain flow compensation during 70° point row operation but uncontrolled transient responses on 20° point row angle. Flow control configuration impacted nozzle flow settling time and off-rate times for different point row angles, ground speeds and application rates. No transient response during ASC actuation was observed for metered 3-way boom shut-off valves whereas the 2-way boom valves exhibited under-damped (exiting point row) and over-damped (reentering point row) response. The nozzle flow settled quicker with metered 3-way boom valves (within 4 s) as compared to the 2-way valve (1 to 28 s) configuration, thereby impacting off-rate times. The regulating valve calibration number also impacted nozzle flow settling times (response). Overall, the total off-rate times for both the 2-way and metered 3-way boom shut-off valve setups increased as ground decreased and point row angle increased. Thus, flow control configuration, control hardware feedback and response, and control algorithms are critical for expected management of crop inputs. In conclusions, the control hardware and algorithms used within controllers must be designed and tuned to minimize off-rate errors. These modifications are specifically critical as the control resolution decreases down to individual nozzle control on future agricultural sprayers.