GreenSpray: Assessing spraying technologies in orchards using CFD modelling

The GreenSpray project aims to promote more sustainable fruit cultivation in Flanders by evaluating, optimizing, and implementing precision spraying methods. The primary objective of the project is to significantly reduce the usage of crop protection products by 2030. In present work computational fluid dynamics (CFD) simulations are employed for the study of the dynamic spraying process for different growth stages and training system of pear trees. A comparative study on canopy and ground deposition was conducted for two different types of nozzle configurations: hollow cone nozzles (TVI) with 90% drift reduction and flat fan nozzles (IDK) with 75% drift reduction, implemented on a crossflow spouts sprayer (H.S.S., NL). The CFD simulation incorporates stochastic spray-canopy interactions due to varying leaf density and properties, further depending on droplet velocity and size. A parametric study was performed to reveal the effect of droplet size distribution (affected by pressure and nozzle type), water volume, tractor velocity and leaf area density. Deposition was analyzed across different vertical zones of the trees. The simulation results showed that the deposition from spraying with flat fan nozzles in a dense spindle tree increased in the top zones of the tree canopy as compared to using hollow cone nozzles. Off-target depositions were generally large indicating the potential of precision spraying techniques avoiding inter-tree spraying. Effects of driving speed and leaf area density were analyzed as well. The results are currently being validated with orchard field trials. The results generated through CFD simulations can serve as a reference with which the grower can estimate the effects of current, adapted and new
techniques and settings on deposition, distribution and losses.