Effect of pressure and nozzle diameter on spray quality and droplet size in handheld gun sprayers

• Droplet size significantly decreased with spray pressure up to 20 bar and nozzle diameters down to 0.22 cm. • Spray pressure (5-20 bar) and nozzle diameter (0.22-0.32 cm) were key factors in spray characteristics and pest control. • Larger nozzle diameters (up to 0.32 cm) produced bigger droplets and reduced drift. • Nozzle and pressure adjustments influenced spray volume and application efficiency. • Optimizing sprayer settings improved spray quality and reduced environmental impact. With the continuous growth of the global population and the persistent challenge of agricultural pests, there is a critical need for effective and precise pesticide applications to ensure sustainable crop production. Spray quality and the efficient utilization of sprayers are key factors for both users and manufacturers. This study investigates the effects of spray pressure and nozzle diameter on the spray quality index, as well as the 50% and 90% volume median diameters (VMD) and numerical median diameter (NMD) in handheld gun sprayers. Experiments were conducted at Khuzestan University of Agricultural Sciences and Natural Resources in 2019. A two-factor factorial experiment was conducted using a completely randomized design (CRD) with three replications. The investigated factors included spray pressure at three levels (5, 12.5, and 20 bar) and nozzle diameter at three sizes (0.22, 0.27, and 0.32 cm). Analysis of variance (ANOVA) revealed that spray pressure and nozzle diameter had a statistically significant effect on the spray quality index, VMD 50%, VMD 90%, and NMD at the 1% significance level. An increase in spray pressure (from 5 to 12.5 and from 12.5 to 20 bar) and a decrease in nozzle diameter (from 0.32 to 0.27 and from 0.27 to 0.22 cm) led to a reduction in droplet size, consequently decreasing VMD 50%, VMD 90%, and NMD. These findings highlight that optimizing spray pressure and nozzle diameter plays a crucial role in controlling droplet size and improving spray quality, ultimately enhancing pesticide application efficiency and mitigating environmental risks by reducing drift. Future studies should investigate a broader range of nozzle types, including electrostatic nozzles, and spraying conditions to refine and optimize pesticide application techniques.