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

Introduction Innovative 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 Methods This 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 consist of an ON-OFF solenoid valve, a digital camera for imaging purposes, an ultrasonic sensor, a flow meter, and a control circuit. Necessary modifications were implemented on a fixed-rate turbine sprayer. The development of the variable-rate sprayer was divided 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 the pesticide solution was conducted across different treatments in two spraying modes, namely variable-rate and fixed-rate, at three distinct speeds: low (1.6 km h), medium (3.2 km h), and high (4.8 km h) resulting in six treatments. Results and Discussion The 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 or 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 h. The maximum efficiency was 70% in the variable-rate spraying mode, occurring at a speed of 3.2 km h. 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 h (1303 L ha), and the highest amount of deposition occurred in the fixed-rate spraying at the speed of 1.6 km h (2121 L ha). The highest amount of pesticide release in the air was also calculated in the fixed-rate spraying mode with a speed of km h (241 L ha) and the lowest value was calculated in the variable-rate spraying mode with a speed of 3.2 km h. Conclusion Emerging technologies, such as smart sprayers, play a crucial role in enhancing the productivity of the agricultural sector. If these technologies are not utilized, the challenges related to the sustainability of production will likely increase in the future. One of the critical operations in agricultural production 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 used to compare the two spraying systems. The findings revealed that, due to real-time control of pesticide application based on canopy volume detection in the variable-rate sprayer, pesticide consumption was reduced by 46% at an optimal speed of 1.6 km h, achieving 70% efficiency. In all 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 significantly impact the amount of pesticide deposition on trees or total pesticide consumption per hectare. There was no significant difference in the coverage percentage of pesticide deposition on targets across different treatments, with the best spraying quality observed in variable-rate spraying at a speed of 4.8 km h. By utilizing a variable-rate sprayer, costs associated with chemical pesticide consumption and spraying can be reduced, while also minimizing toxic emissions that contribute to environmental pollution. Future research should focus on developing a variable-rate system based on independent nozzles, allowing for real-time control of each nozzle's spraying.