Due to its ability to broaden the transport channel of droplets within the plant canopy and enhance their penetration capacity, air-assisted spray technology is widely used in orchard pesticide application. To achieve uniform distribution of pesticide droplets in the tree canopy and obtain a higher pesticide utilization rate, it is crucial to clarify the coupling mechanism of the airflow field and droplet field generated by the air-assisted sprayer. This paper introduces a three-dimensional modeling method of the fruit tree canopy based on CFD (Computational Fluid Dynamics), offering a theoretical basis for analyzing the airflow demand calculation during different growth periods of the canopy. It also examines the interaction between canopy modeling and airflow, highlighting advancements in airflow regulation equipment and the effects of airflow speed and volume on spraying. The study shows that the precise regulation of airflow velocity and discharge rate is of importance for improving spraying efficiency. It finally points out that future research should focus on developing intelligent regulation equipment for efficient airflow-droplet control, using biomass sensing, which involves measuring the growth characteristics of the tree canopy, to meet the needs of orchards with diverse growth stages and canopy structures. This article could provide guidance for the future study of precision air-assisted spraying technology in orchards.

Plant nursery presents the characteristics of close planting. It is difficult for the traditional air-assisted sprayer to take into account the dual requirements of "long spray range and uniform droplet deposition", which leads to the problems of low deposition and drift.A goose-neck long-range air-assisted sprayer for nursery was designed based on CFD simulation and free submerged jet theory. The three-outlet flow guide device, as the core component of the sprayer, has outlets A, B, and C. Air outlet A adopts a circular arc shape, while air outlet B and air outlet C are gradually expanding circular arc tubes. The three air outlets are interconnected and correspond to different areas, which can meet the requirements of far-range spray operation. The optimized curvature radius parameters are conducive to maintaining a uniform and stable flow state of airflow. Based on the free submergence jet theory, the air outlet and fan parameters were determined, and airflow field distribution measurement experiments were conducted. when the fan speed is no less that 2 200 r/min, the airflow speed can fit the spraying requirement as far as 20 m. The average airflow speed was 2.33 m/s at a height of 0.8 m ; the airflow speed was 1.74 m/s at 20.0 m. The variation coefficient of airflow speed at different heights was less than 30%, indicating that the energy attenuation rate was slow and uniform, and the airflow could carry droplets to spray far away at a uniform speed. The droplet deposition test shows that the variation coefficient of the droplet deposition amount of the goose-neck long-range nursery air spray is 28.87%. To ensure the reliability of our findings,a comprehensive field test of the sprayer were conducted. Citrus seedlings, with an average height of 80 cm, were chosen as the test subjects, and the test was carried out in the nursery of the Citrus Research Institute of Chongqing Southwest University. Following the guidelines of GB/T17997-2008, the droplet deposition effect and drift rate at various distances were tested .The experimental results show that the fan speed of the sprayer is 2 400 r/min and the driving speed is 1 m/s; the droplet deposition tends to be less-more-less with the increase of distance. The droplet coverage rates of the upper and lower leaves of the canopy were 51.93% and 24.38%, respectively, and 42.99% and 19.26%, respectively. The average droplet deposition on the front and back leaves of the upper canopy was 13.34 and 2.82 µL/cm², respectively, and that on the lower canopy was 5.44 and 2.63 µL/cm², respectively, which met the requirements of plant protection spraying operation. It can be seen that the sprayer shows good spray range performance and droplet deposition uniformity, which can meet the agronomic requirements of the complex planting environment in the nursery and the industrial standards of the air-assisted sprayer. At present, in Chinese nurseries such as citrus, pear, and apple, etc, manual machinery accounts for a large proportion of spraying equipment, and the demand for specialized sprayers is becoming increasingly urgent. Due to the close planting mode of the nursery, it can be considered that the two modes of spray with high clearance spraying and long-range airflow-assisted spraying have application prospects. Compared with high-clearance spraying, long-range airflow-assisted spraying has the characteristics of high operating efficiency and good horticultural trafficability and is more suitable for small and medium-sized nurseries. However, improving the delivery distance of aerosol flow while ensuring good uniformity of droplet deposition is still a challenge. The results of this study can provide a new idea for developing a long-range air-assisted sprayer for nurseries.

Facility operation is often required to alleviate the soil-borne diseases that are caused by the long-term heavy stubble in greenhouses. Particularly, the planting pattern is mostly highly intensive in Chinese greenhouses at present. The long-term heavy stubble has led to a low nutrient balance in the soil. The pathogenic bacteria and insect eggs can continue to multiply and expand, thus infecting the roots and stems during crop reduction. Therefore, it is very urgent to consider soil flame disinfection. It is expected to integrate the disinfection, fine deep tillage, and ridge forming, in order to avoid the repeated operation of machinery. In this study, an integrated operation of "straight blade crushing - scraper throwing - flame disinfection – ridge forming" was adopted in the facility greenhouse. The optimal combination of operation parameters was also clarified to improve the quality of operation. A soil disinfection and ridge-forming machine was designed using a fine rotary flame. The main components included rotary tillage and soil crushing, ridge forming, flame disinfection, and electronic lighter devices. In the rotary tillage and soil crushing device, the blade roller of soil crushing was mainly composed of straight blades and scrapers arranged on the blade shaft, according to the spiral line. The major component was utilized to facilitate into the soil. The soil fragmentation rate and the efficiency of rotary tillage were also compared with the conventional rotary tillage blade roller using simulation. The results showed that the better performance of soil crushing blade roller was achieved during soil crushing and throwing, compared with the conventional one. There was an increase in the total number of soil fracture bonds caused by the soil-crushing blade roller. The better performance of flame disinfection was also obtained to optimize the parameters of the machine. Meanwhile, the heat demand for the soil disinfection was 958.23 kJ per second, and the heat supply of the machine was 978.72 kJ per second, which was greater than the heat demand. The soil was heated from 0-10 cm to 71.8 °C and from 11-14 cm to 51 °C, corresponding to the lethal temperature requirements of pathogenic microorganisms and root-knot nematodes, respectively. Single- and multi-factor field tests were carried out to verify the performance of the machine. The evaluation indicators were taken as the qualified rate of ridge type, as well as the insecticidal and sterilization rate. The influencing factors were the blade shaft speed, machine walking speed, and tillage depth. The best combination of operating parameters was obtained after optimization. The field tests showed that the primary and secondary factors on the machine's performance were ranked in descending order of the machine's walking speed, blade shaft speed, and tillage depth. The qualified rate of ridge type was 95.2%, while the insecticidal and sterilization rate was 82.9% when the blade shaft speed was 270 r/min, the machine walking speed was 0.63 m/s, and the tillage depth was 22 cm. Among them, the qualified rate of ridge type fully met the ridge standard, while the insecticidal and sterilization rate was close to the national standard. The operating cost and CO₂ emission of the machine were compared with the dazomet mechanical soil disinfection. The operating cost was RMB 4 543 yuan per hectare, thus saving RMB 7 087 yuan per hectare, compared with the dazomet mechanical soil disinfection. The CO₂ emission was 1 341 kg per hectare, indicating the promising prospect of application. The finding can also provide guidance for the practical application of the facility greenhouse, particularly for the soil disinfection and ridge-forming machine using a fine spiral flame.