Highlights Static and dynamic performance of an agricultural sprayer was evaluated. Nozzle flow variation was lowest (0%) at PWM 40, ensuring stable spray output. Best spray quality index (2.28) achieved at 4.44 m·s-1 with PWM 40 operation. Average field capacity of 8.27 ha.h-1 with 72.5% operational efficiency achieved. Abstract. The precise and targeted application of agrochemicals is critical for effective pest and disease management, sustainable crop production, and minimizing environmental impact. Agricultural spraying UAVs have emerged as a promising alternative to conventional ground-based sprayers, offering improved accuracy, uniformity, and operational efficiency. By enabling smarter and more precise chemical delivery, these technologies support healthier crops and represent a key advancement towards modern, technology-driven farming systems. However, comprehensive evaluations of their static and dynamic performance under varying operating conditions remain limited. This study evaluated a 20-L agricultural spraying UAV through a series of static (laboratory/workshop) and dynamic (field) tests. Static assessments included measurements of actual tank capacity, calibration accuracy of the tank scale markings, and nozzle flow-rate uniformity across different pump motor speeds (PWM levels: 40, 50, 75, 100). Dynamic field tests investigated effective spray width, spray quality, and droplet drift under different combinations of PWM levels and forward speeds (4.44–6.11 m·s -1 ), with three replications per treatment. Results showed that the coefficient of variation (CV) of nozzle flow rates ranged from 0% at PWM 40 to 2% at PWM 50 and 75. The lowest (more favorable) spray quality index (2.28) was observed at a forward speed of 4.44 m·s -1 with a PWM 40. Droplet drift, defined as the percentage of droplets reaching unintended areas away from the target plants, was estimated at 14% at 4.44 m·s -1 . The application rate ranged from 17.43 to 38.28 L ha -1 , depending on speed and PWM settings. The average actual field capacity and operational efficiency were 8.27 ha·h -1 and 72.5%, respectively. Overall, the tested UAV demonstrated acceptable performance in flow regulation, spray distribution, and operational efficiency, indicating its suitability for precision agrochemical applications, provided that concerns such as spray drift, cost, and regulatory barriers are addressed. This study shows that evaluating the performance of UAV-based precision spraying is important for supporting better crop health in future agriculture. (Pulse width Modulation: A key component of pulse width modulation (PWM) is the duty cycle, which is defined as the ratio of the pulse width to the whole time period.) Keywords: Drones, Dynamic and static tests, Operational efficiency, Spray quality.
Liu et al. (Thu,) studied this question.