Influence of the Spray Jet Angle on the Partition, Spatial Distribution and Transfer of a Pesticide Spray Solution on Coffee Plants

Efficient deposition on coffee (Coffea arabica L.) is challenging, especially on the abaxial surface. Conventional calibration ignores the spray that crosses the canopy (transfer), generating losses. We evaluated three spray nozzle configurations (80°, 90° and 40°-90°-60°) in the spatial distribution of the deposition in commercial crops (turbo sprayer, 400 L ha−1, 5.63 km h−1), in a 3 × 2 factorial design (angles × sides of application). The Bright Blue tracer was quantified by spectrophotometry in the reference and transfer fractions, stratifying the canopy into thirds (upper, middle, lower), positions (external, internal) and leaf surface (adaxial, abaxial). The data were submitted to Linear Mixed-Effect Models (LMMs). The results revealed an operational trade-off: the 90° angle maximized uniformity on the target but produced the highest transfer; the 80° pattern retained more spray, with less uniformity; and the combined configuration (40°-90°-60°) was efficient for vertically directed targets. The canopy architecture exceeded the application parameters in the upper third, inverting the pattern and favoring abaxial deposition. Furthermore, deposition asymmetry between application sides supported the hypothesis of airflow distribution imbalances inherent to the axial fan. We conclude that the choice of angle requires a compromise between uniformity and retention. Quantifying transfer deposition highlights the limitations of standard volumetric calibration for axial-fan sprayers, underscoring the need for application technologies that optimize canopy retention while mitigating potential losses.