A real-time variable rate air and liquid sprayer for orchard applications

Abstract Purpose Efficient orchard spraying requires uniform canopy coverage while reducing pesticide drift and application rates. To achieve this, variable rate applications (VRA) are preferred. However, most current studies on VRA focus on directing the spray liquid to the tree canopy. To address these challenges, a real-time variable-rate air-assisted orchard sprayer was developed, integrating laser sensors and a hydraulic-driven turbofan controlled by LabVIEW software. Methods The objective of this study was to develop a real-time variable-rate orchard sprayer capable of controlling the outgoing airflow as well as the spray liquid based on canopy characteristics. Prior to testing, the sprayer was adapted to each orchard, and its performance was evaluated through deposition and drift trials under different canopy geometries and leaf densities. Results With VRA, air velocities were maintained between 3 and 5 m s⁻¹ at the canopy’s outer edge, a range critical for achieving adequate air capacity and droplet transport within tree canopies. VRA left 25% of the conventional application (CA) tracer on leaves, yet this value was considered adequate when the spray index data was analyzed. VRA also achieved drift reductions in ground losses (86.95%) and airborne drift (89.98%). Conclusion The system’s trigger mechanism, guided by real-time canopy data from laser sensors, proved adaptable to diverse orchard conditions. Thanks to the sprayer, more successful spraying with less drift was achieved with less pesticide usage (69.90%) and less fuel consumption (14.78%). These findings highlight the potential of this precision agriculture technology to enhance spraying efficiency, conserve resources, and minimise environmental impact.