Modeling of spray penetration and deposition on citrus tree canopies

A simulation model has been developed to estimate spray deposition from air-carrier tower sprayers on orchard trees under different application conditions. The model includes spray transport from the sprayer to the canopy and spray displacement within the canopy. Spray velocity and mass flux at canopy boundaries were estimated. Spray velocity at the boundary was used to calculated spray velocity inside the canopy as a function of canopy depth and density. Spray velocity inside the canopy was coupled with mass flux to obtain deposition at canopy depths. Sensitivity of the model was evaluated for liquid flow rate, leaf area density, sprayer-tree distance, canopy diameter, tree height, airflow rate, and ground speed. Simulated air velocities and canopy depositions were in general agreement with the measured data. Deposition increased with liquid flow rate but decreased with increasing tree height and ground speed. Canopy diameter did not affect deposition. In the near side of the canopy, deposition increased with increasing maximum leaf area density and sprayer-tree distance but decreased with airflow rate.