An air-assisted electrostatic nozzle uses a combination of air-assisted atomization and electrostatic spray technology. This article optimizes the existing air-assisted electrostatic nozzles in terms of structural design to obtain a higher charge-to-mass ratio and a smaller droplet size. The optimized air-assisted electrostatic nozzle was studied experimentally, and the effects of liquid pressure, air pressure and applied voltage on the droplet size and charge-to-mass ratio were investigated. Comparing the effects of air pressure, liquid pressure and applied voltage on the charge-to-mass ratio and droplet size, the relationship curves of the droplet size and charge-to-mass ratio under each voltage were fitted using the Rayleigh charge limit theory. For a higher CMR during the spray operation, applied voltages between 2.5 kV and 3 kV, an air pressure between 0.4 bar and 0.6 bar, and a liquid pressure of less than 0.9 bar could be chosen. The optimized air-assisted electrostatic nozzles not only have small droplets but also have high charge-to-mass ratios, reducing the need for pesticide use and thus protecting human health and the environment.

Pollination is essential to maintain ecosystem balance and agricultural production. Domesticated bee pollination, which is easy to feed and manage, and mechanized pollination, which is not restricted by the environment, are considered the main technical means to alleviate the “pollinating insect crisis”. By analyzing differences in pollination methods for different crops, this review summarizes the research progress for efficient pollination technology from the perspectives of bee pollination and mechanized pollination in fields, orchards, and greenhouses. The selection of pollination method should be based on the physiological characteristics of crops and the actual environmental conditions of natural pollination. The pollination ability of bees is closely related to the status of the bees. Maintaining the pollination ability of bees in a reasonable range is the goal of bee pollination services. Colony state control technology needs to develop in two directions. First, there is a need to develop colony state monitoring technology based on multi-feature information fusion and to explore the self-regulation mechanisms of the colony in response to various factors. Second, based on these self-regulation mechanisms, there is a need to develop a low-cost and non-invasive bee colony state and pollination capacity estimation model, monitoring technology, and equipment based on single feature information. The goals of mechanized pollination are “efficiency” and “precision”. Mechanized pollination technology needs to be developed in two directions. First, the mechanisms of pollen abscission, transport, and sedimentation in different crops and mechanized pollination conditions should be explored. Second, research and development of efficient and accurate pollination equipment and technology based on the integration of multiple technologies such as pneumatic assistance, auxiliaries, static electricity, target, variables, and navigation, are needed.

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.

This paper presents an air-assisted sprayer for vineyard pesticide application. The spraying unit was designed with two symmetrically arranged ports. The airflow velocity distribution of the sprayer was investigated using a combination of experimental validation and a computational fluid dynamics (CFD) model. The results of both the simulation and the experiment showed good agreement in airflow velocity, and the distribution was uniform. Both unilateral and bilateral spraying field experiments were conducted in this study. The unilateral spraying experiment showed that higher spray pressure and lower sprayer speed increased both total deposition coverage and spray penetration (SP), while shorter spray distances improved SP but decreased total deposition coverage. The optimal operational conditions for the sprayer were determined as follows: spray pressure of 0.40 MPa, sprayer speed of 0.83 m/s, and spray distance of 1.00 m. The results of the bilateral spraying field experiment indicated that the coefficient of variation (CV) for deposition coverage in Columns A, B, and C were 16.20%, 8.10%, and 15.47%, respectively. The CVs in Layers a, b, and c were 6.14%, 12.62%, and 6.74%, respectively. This result demonstrated that the deposition coverage distribution in the canopy was relatively uniform, and the air-assisted sprayer exhibited good spray penetration performance. This study demonstrates the effectiveness and potential of the air-assisted sprayer for vineyard pesticide application.

Variable-rate spray systems with canopy leaf area density information detection are an important approach to reducing pesticide usage in orchard management. In order to estimate the canopy leaf area density using ultrasonic sensors, this article proposed three parameter model equations based on ultrasonic echo peaks for canopy leaf area density estimation and verified the accuracy of the three parameter model equations using laboratory-simulated canopy and outdoor tree experiments. The orthogonal regression statistics results from the laboratory-simulated canopy experiment indicated that parameter ${\mathrm{V}}_{\mathrm{c}}$ is more suitable for canopy leaf area density estimation compared to parameter ${\mathrm{V}}_{\mathrm{a}}$ and ${\mathrm{V}}_{\mathrm{b}}$ when the density ranges from 0.54 to 5.4 ${\mathrm{m}}^2{\mathrm{m}}^{-3}$. The model equation from parameter ${\mathrm{V}}_{\mathrm{c}}$ has minor systematic errors, and the predicted and observed values of parameter ${\mathrm{V}}_{\mathrm{c}}$ have good agreement with the experimental conditions. The laboratory-simulated canopy and outdoor tree canopy leaf area density verification experiments of parameter ${\mathrm{V}}_{\mathrm{c}}$ were carried out, and the results indicated that the absolute value of the mean relative error is 5.37% in the laboratory-simulated canopy and 2.84% in outdoor tree experiments. The maximum absolute value of the relative error is 8.61% in the laboratory-simulated canopy and 14.71% in the outdoor tree experiments, and the minimum absolute value of the relative error is 3.21% in the laboratory-simulated canopy and 0.56% in the outdoor tree experiments. The laboratory-simulated canopy leaf area density verification results showed that the mean relative errors under canopy leaf area density 0.98 and 4.92 ${\mathrm{m}}^2{\mathrm{m}}^{-3}$ conditions are 6.29% and 5.82%, respectively, which is larger than the mean relative error under 2.95 ${\mathrm{m}}^2{\mathrm{m}}^{-3}$; nevertheless, these results proved that this model equation is applicable for canopy information detection and advanced pesticide application development in future.

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.