Design, manufacturing and effectiveness analysis of variable ratio air and liquid applied sprayer for fruit trees

In our country, standard type air assissted orchard sprayers are widely used to apply pesticides to fruit trees. With this type of sprayers, it is not possible to change the application volume (L/tree) depending on the tree crown volume, to change the air flow instantaneously, and to instantly cut the pesticide in the gaps between trees. In applications made with air assissted orchard sprayers, studies are generally carried out on variable rate spray systems to save pesticides. However, along with the control of the spray system, the droplet carrier air flow must also be controlled. In this study; The axial fan of a newly designed air assissted orchard sprayer is operated by a separate hydraulic system, and a variable rate spray system is created by controlling the variable rate air flow and the nozzles on the spray system independently with solenoid valves. In the study, the geometry of the tree canopy was instantly detected through laser sensors, and then these data received with the sensors were used to calculate the amount of liquid and airflow velocity required for spraying, thanks to the program called Labview. Thus, as the orchard sprayer moves through the rows, it can apply real-time air and spray liquid depending on the changing geometries of the tree and therefore the canopy volume. Before the orchard trials, preliminary studies were carried out in a laboratory environment to enable the sprayer to have an instantaneous and own decision-making mechanism. The sprayer, produced as a prototype, was tested in grapefruit (LAI=2.08), pecan walnut (LAI=1.67) and persimmon (LAI=1.49) orchards with different canopy geometries and leaf densities. The designed orchard sprayer can be operated as both variable rate and traditional orchard sprayers (15, 30, 45⸰ fan blade angle and 1680 and 2160 rpm fan rotation speed). In the trials, the designed orchard sprayer; it was operated in 7 different operating conditions, including variable rate and traditional application (6 different applications), in 3 different orchards. In order to compare both the variable rate application performance of the new design and the efficiencies achieved under traditional operating conditions, the amount of drift (BSF trace substance) deposits (μg/cm2) and coverage rates (%),deposits that drifted out of the tree canopy (airborne drift) in selected areas on the tree, residue reaching the ground under the tree crown (ground drift) and energy consumption values for each operating condition were measured.In variable rate applications, 58.55% less pesticide was consumed in grapefruit trees, 69.90% in pecans, and 68.01% in persimmons compared to traditional applications. In the trials carried out with traditional application, the application volume in grapefruit and pecan orchards was determined as 550 L/ha, and the application volume in persimmon was determined as 830 L/ha. In the study with the specified application volumes, the average trace material accumulation measured on the grapefruit tree in variable rate applications was 2.77 μg/cm2, the coverage rate was 13.74%, drift losses were 0.96 μg/cm2 and the trace material accumulation reaching the ground was 2.88 μg/cm2 measured.These values were respectively: the average tracer accumulation in pecan nuts was 2.79 μg/cm2, the coverage rate was 14.79%, the drift losses were 0.78 μg/cm2 and the tracer accumulation reaching the ground was 4.86 μg/cm2. In persimmon, trace material accumulation was measured as 2.80 μg/cm2, coverage rate was 14.20%, drift losses were 1.41 μg/cm2 and tracer accumulation reaching the ground was measured as 10.08 μg/cm2. Variable rate applications generally provided lower tracer deposit and coating values than conventional operating conditions. In trials conducted with variable rate application, regardless of tree type, fuel savings of 10% were achieved. Keywords: Variable Rate Air and Liquid Application, Air Assissted Orchard Sprayer, Laser Sensor, Orchard Spraying, Deposition, Drift