Prototype manufacturing of a variable rate spraying system for fruit trees

Because of the continuous spraying without regard to the trees' row space and canopy volume, excessive amounts of water and chemical pesticides are used when applying pesticides to fruit trees with conventional orchard sprayers. This approach causes unnecessary pesticide use, negatively affecting issues such as spraying costs and human and environmental health. As it is known, each tree's geometric dimensions and canopy structures (canopy shape, leaf density, etc.) are different from each other, and therefore, it may be necessary to apply different amounts of pesticides to each tree for successful spraying. In this study, the canopy volume was calculated in real time by means of ultrasonic sensors attached to the spray unit of a standard orchard sprayer for variable rate pesticide applications, and simultaneously, pesticide applications were made proportional to the canopy volume with hydraulic nozzles operated with Pulse Width Modulation (PWM). The obtained results were compared with continuous spraying. Spray deposits, coverage values, and off-target losses in selected regions of the tree canopy were determined as comparison parameters. When the obtained results were evaluated in terms of the amount of pesticide applied by considering only the tree canopy geometry, the prototype system with variable rate spraying provided a 48,69% savings in application volume and an 88,67% reduction in off-target losses compared to the conventional system with constant rate spraying.