Comparison and Evaluation of Common Orchard Sprayers with Variable-rate Sprayers

IntroductionInnovative technologies, such as smart sprayers, are pivotal catalysts for modernizing the agricultural sector and play an indispensable role in providing food for human consumption. Without the utilization of these technologies and the implementation of proper input management, it is predicted that environmental impacts will worsen in the future. Attaining sustainable production, while implementing programs to ensure food security, presents a considerable challenge for researchers and policymakers worldwide. In this research, the performance of a fixed-rate orchard sprayer was evaluated. Employing various equipment, the sprayer was then upgraded to a variable-rate sprayer, and its performance was reevaluated and compared to the fixed-rate model.Material and MethodsThis research comprehensively evaluated a fixed-rate orchard sprayer and subsequently upgraded it to a variable-rate sprayer for further assessment. The primary components of the developed variable-rate sprayer, consists of an ON-OFF solenoid valve, a digital camera for imaging purposes, an ultrasonic sensor, a flow meter, and a control circuit. The necessary modifications were implemented on a fixed-rate turbine sprayer. The development of the variable-rate sprayer was devided into two distinct phases. The initial phase involved determining the canopy volume and acquiring the necessary information pertaining to the spraying target, specifically the tree. The subsequent phase focused on decision-making and control of the spraying rate, thereby facilitating variable-rate application. Upon laboratory examination of the samples, spectroscopic results were obtained, and the total concentration of the pesticide solution was calculated across different sections of a one-hectare orange orchard. An investigation into the sedimentation of pesticide solution was conducted across different treatments in two spraying modes namely, variable-rate and fixed-rate and at three distinct speeds: low (1.6 km hr-1), medium (3.2 km hr-1), and high (4.8 km hr-1) resulting in six treatments.Results and DiscussionThe comparative analysis of average pesticide deposition on trees revealed a significant difference between the two spraying modes; variable-rate and fixed-rate. All indicators demonstrate that the type of sprayer and the spraying speed significantly influence changes in pesticide deposition across different treatments. However, the interaction effect of the type of sprayer and the speed of spraying did not significantly impact the amount of pesticide deposition on the trees and the total consumption of pesticide per hectare. The results indicated that neither the type of sprayer, nor the speed of spraying, nor their interaction had a significant effect on the spraying quality index. Furthermore, the numerical median diameter and volume median diameter were not significantly different across the treatments.The maximum pesticide consumption savings in the variable-rate spraying mode was 46%, achieved at a speed of 1.6 km hr-1. The maximum efficiency was 70% in the variable-rate spraying mode, occurring at a speed of 3.2 km hr-1. The lowest amount of pesticide deposition on the canopy of trees was observed in the variable-rate spraying method at the speed of 4.8 km hr-1 (1303 L ha-1), and the highest amount of deposition occurred in the fixed-rate spraying at the speed of 1.6 km hr-1 (2121 L ha-1). The highest amount of pesticide release in the air was also calculated in the fixed-rate spraying mode with a speed of km hr-1 (241 L ha-1) and the lowest value was calculated in the variable-rate spraying mode with a speed of 3.2 km hr-1.ConclusionEmerging technologies, such as smart sprayers, play a crucial role in increasing the productivity of the agricultural sector. If these technologies are not utilized, the challenges related to the sustainability of production will increase in the future. One of the critical operations in the production of agricultural products is the spraying phase. In this research, a fixed-rate sprayer was upgraded to a variable-rate sprayer, both sprayers were evaluated, and the results of this evaluation were then used to compare the two spraying systems. The results revealed that because the amount of the pesticide sprayed is controlled in real time by canopy volume detection in the variable-rate sprayer, in the best case (speed 1.6 km hr-1), it reduced pesticide consumption by 46% and reached 70% efficiency. In all the studied treatments, both the type of sprayer and the speed of spraying significantly affected changes in pesticide deposition. However, the interaction between the type of sprayer and the speed of spraying did not have a significant effect on the amount of pesticide deposition on trees or total pesticide consumption per hectare. There was no significant difference in the coverage percentage of the pesticide deposition on the target in different treatments, and the best spraying quality occurred in variable rate spraying with a speed of 4.8 km hr-1.By using a variable-rate sprayer, while saving on the costs of chemical pesticide consumption and spraying, toxic emissions that cause environmental pollution will also be reduced. Future research should focus on developing a variable-rate system based on independent nozzles, allowing for real-time control of each individual nozzle's spraying..