Air-assisted spraying is vital in modern orchard pest management by enhancing droplet penetration and coverage on complex canopies. However, the interaction between airflow, droplets, and flexible foliage remains unclear, limiting spray efficiency and environmental sustainability. This review summarizes recent advances in understanding leaf motion dynamics in wind and droplet fields and their impact on pesticide deposition. First, we review orchard spraying technologies, focusing on air-assisted systems and their contribution to more uniform coverage. Next, we analyze mechanisms of droplet deposition within canopies, highlighting how wind characteristics, droplet size, and canopy structure influence pesticide distribution. Special attention is given to leaf aerodynamic responses, including bending, vibration, and transient deformation induced by wind and droplet impacts. Experimental and simulation studies reveal how leaf motion affects droplet retention, spreading, and secondary splashing. The limitations of static boundary models in deposition simulations are discussed, along with the potential of fluid-structure interaction (FSI) models. Future directions include integrated leaf-droplet experiments, intelligent airflow control, and incorporating plant biomechanics into precision spraying. Understanding leaf motion in spray environments is key to enhancing orchard spraying efficiency, precision, and sustainability.

To address practical issues, such as uneven fertilizer distribution and poor particle dispersion, during the operation of a centrifugal double-disc fertilizer spreader, a discrete element method (DEM) simulation was initially performed. In this simulation, the blade inclination angle, fertilizer discharge offset angle, and spreading height were selected as experimental factors. The spreading width and the coefficient of variation (C_v) of fertilizer uniformity served as evaluation indicators. A quadratic orthogonal simulation experiment was designed to evaluate spreading performance. Subsequently, regression equations were established to optimize parameters and determine the optimal design configuration. Experimental results showed optimal performance with a blade inclination angle of −5°, fertilizer discharge offset angle of 45°, spreading height of 1050 mm, and disc rotational speed of 400 rpm. Considering that fertilizer spreaders are susceptible to air resistance and environmental wind during field operations, an EDEM-CFD coupling method was employed to simulate realistic operating conditions. Virtual simulation results demonstrated optimal fertilizer spreading performance at disc rotational speeds ranging from 350 to 400 rpm under tailwind conditions, and from 400 to 500 rpm under headwind conditions. Based on the simulation results, a prototype was built and tested. The experimental results closely matched the simulation predictions, thereby confirming the effectiveness of the simulation model. This study provides valuable insights and serves as a reference for designing and optimizing fertilizer spreader performance under practical operational conditions.

To realize the online evaluation of spray quality, an online measuring system for spray coverage and deposition quality is developed. The measuring theory of spray coverage and deposition quality on an LWS (leaf wetness sensor) surface is analyzed. When the spray conditions are constant, there is a linear correlation between the spray coverage on the sensor surface, the spray deposition quality and the LWS output voltage increment. The results of calibration experiments show that when the spray conditions are constant, the coefficient of determination $R^2$ of the regression curves between the sensor output voltage increment and the spray coverage on the sensor surface is more than 0.75, and the coefficient of determination $R^2$ of the regression curves between the sensor output voltage increment and the spray deposition quality on the sensor surface is more than 0.90. Based on ZigBee wireless sensor technology, this paper reports an online measuring system for spray coverage and deposition quality at multiple points in the field. The test results show that the online measuring system has good uniformity. Field test results show that the LWS voltage increment and the coverage rate of water-sensitive paper have a good correlation, and the measuring results of the spray deposition quality trend are in good agreement. The fit of the spray deposition quality curves measured by the two methods was 0.8924. The research results in this paper can provide a reference for using LWS sensors to measure spray coverage and deposition quality.

The dynamic evaporation of single droplets was investigated under controlled conditions. In the evaporation process, a droplet was placed on a peach leaf surface. In this research, the relative humidity and temperature were kept constant, and the wind speeds and thiophanate-methyl concentrations varied. Based on these conditions, this study aimed to determine the droplets’ dynamic transforming characteristics, including the contact angle, the height of the droplets, and the evaporation rate. Five concentrations and five wind speeds were chosen, and pure water droplets at different wind speeds were used as a control group. All single droplets were generated by a syringe. The results showed that the pure water and thiophanate-methyl droplets’ evaporation mode was CCR (constant contact radius) mode. An increase in the wind speed accelerated the evaporation process, when the wind speed was 0 m/s, the evaporation was the longest, and the shortest evaporation was achieved with 2.0 m/s wind speed. An increase in wind speed enhanced the pure water droplets’ dynamic evaporation process with a maximum enhancement ratio of 3.44 times in the present work. Under the same conditions, the thiophanate-methyl droplets’ evaporation time was shorter than that of the pure water droplets. For thiophanate-methyl droplets, the higher the concentration, the shorter the dynamic evaporation process. A 1250 ppm thiophanate-methyl solution with 2.0 m/s wind speed, had an evaporation ratio that was 2.83 times greater than that measured with 0 m/s wind speed. These results could benefit farmers by suggesting that they should adjust the concentration of thiophanate-methyl depending on the wind speed in order to reduce pollution.

Air-assisted sprayers are widely used in orchards due to their efficiency in enhancing droplet penetration and deposition. These sprayers disperse droplets through a high-velocity airflow, which agitates the leaves and aids in canopy penetration. This study involved controlled experiments to simulate leaf movement during field spraying, with a focus on the dynamics of peach tree leaves (Prunus persica) in varying wind fields. An experimental setup consisting of a wind-conveying system, a measurement system, and a fixed system was designed. The moving speeds of the wind field (0.75 m/s, 0.5 m/s, and 1.0 m/s) and wind velocities (ranging from 2 m/s to 8 m/s) were varied. Key parameters, including leaf tip displacement, angular velocity, and twisting amplitude, were measured using high-speed cameras and motion analysis software. The results indicate that, at a constant wind velocity, increasing the wind field’s moving speed resulted in a reduced range of motion, decelerated angular velocity, and decreased twisting amplitude of the leaves. Notably, at a wind field speed of 8 m/s and a moving speed of 1.0 m/s, the twisting duration of the leaves was only 67% of that observed at a moving speed of 0.5 m/s. These findings suggest that wind speed and field motion characteristics play a crucial role in leaf dynamics, informing the design of air-assisted spraying systems.

High clearance sprayer is a high-efficiency pesticide application machine in orchard management. In this paper, operational safety of high clearance sprayers is validated by using finite element simulation and vibration testing. The 3D model of the frame is simplified by using shell units instead of solid units, the static performance of high clearance sprayer frames under static full load and ultimate torsional conditions was studied by means of finite element simulation tests, the mechanical properties of the frame under step excitation were studied by multi-body dynamic simulation test. The simulation results show that, at a safety factor of 1.5, the maximum stress extremes in the frame are within the safe permissible stress range. During the dynamics analysis, a tire-ground contact simplified model was proposed. The results of the modal analysis show that the inherent frequency distribution of the high clearance sprayer is compact, and the vibration test has measured a large difference between the engine vibration frequency with the inherent frequency of the frame, this means that resonance will not occur. The theoretical analysis shows that the designed high clearance sprayer meets the requirements of large cross-row field operations, the study provides a reference for the overall design of the high clearance sprayer.