BACKGROUND Pesticide losses and uneven spray distribution should be avoided as much as possible as they reduce the effectiveness of spraying and increase environmental contamination as well as costs. Within the H2020‐project OPTIMA the goal is to develop a smart sprayer for bed‐grown carrots, including optimizations such as air support and variable nozzle spacing. This paper focuses on selecting the most optimal nozzle types, spacing and height for spraying bed‐grown crops, while taking into account different target zone widths depending on the growth stage, based on spray distribution and droplet characterization measurements. RESULTS The results indicate that four bed spray configurations consisting of four nozzles per bed, i.e. XR8004/XR8004/XR8004/XR8004, AIUB8504/AI11004/AI11004/AIUB8504, AI8004/AI8004/AI8004/AI8004 and XR8002/XR8002/XR8002/XR8002, spraying at 300 kPa and recalculated to 12.0 km h−1 forward speed, are appropriate for spraying different target zone widths (ranging from 1.2 to 2.2 m) with high uniformity (CV < 12%) and minimal losses out of the target zone (<17%) when applied at the most appropriate nozzle spacing and height (varying from 0.35 to 0.65 m). Droplet characterization measurements showed that for the same nozzle size and spray pressure, air inclusion nozzles produced larger but slower droplets than standard flat‐fan nozzles. Air support increased the droplet velocities but had only a very limited effect on droplet size. CONCLUSION Laboratory spray distribution and droplet characterization measurements allowed selection of the most optimal nozzle type, spacing and height for bed spray applications in terms of reduced pesticide losses compared to conventional broadcast applications. © 2022 Society of Chemical Industry.

The H2020-project OPTIMA concept of smart sprayer relies on several functionalities, including variable nozzle spacing for bed-grown carrots, based on an air-assisted boom sprayer. A prototype boom was designed and evaluated though canopy deposition, ground losses, and spray drift potential. Four bed spray configurations, including various nozzle types, angles, and sizes (XR8004, combination of AIUB8504/AI11004, AI8004, and XR8002) at the most appropriate nozzle spacing and height, were tested and compared to a broadcast application (XR11004). Deposition measurements were performed on carrots in bins at early and full-grown stages with respective target zone width of 1.4 m and 2.2 m. Spray drift potential measurements were performed following ISO 22401, 2015. The spray boom was equipped with an air sleeve providing different air speeds (0, 4, 8 m s−1). The relative depositions at both growth stages showed a significant effect of spray configuration and lowest values were found for the broadcast application. The configurations consisting of air inclusion nozzles generated the lowest drift potential compared to the broadcast application, although not significantly different. Bed spray configurations can thus improve canopy depositions and spray drift potential compared to a conventional broadcast application when the boom height and the nozzle spacing are adjusted to the growth stage.