Over the past few years, the extensive use of pesticides and chemical fertilizers in China has grown into a significant issue, leading to severe environmental contamination and posing risks to food safety. This has prompted a group of forward-thinking individuals in the field of precision agriculture to explore solutions aimed at enhancing pesticide efficiency and reducing usage through the precise application of agricultural drones. These drones are seen as a potential tool to address some of the pressing environmental and agricultural concerns.
Currently, within the industry focused on the precise application of agricultural drones, most discussions revolve around controlling the flow rate of nozzles. However, the importance of spray droplet size in achieving effective pesticide control, particularly in variable applications, is often overlooked. Let's delve deeper into how agricultural drones can manage both droplet size and flow rate to optimize pesticide effectiveness, boost usage efficiency, and minimize ecological harm.
Droplet Size – A Critical Factor in Drone Spraying Efficiency
The efficacy of pesticide spraying depends heavily on several factors, including droplet size, drift tendencies, and sedimentation velocity. Among these, droplet size is a relatively straightforward parameter to control and plays a crucial role in determining the quality of spraying operations conducted by agricultural drones.
Effectively managing droplet size is essential for minimizing pesticide usage while maximizing control outcomes and reducing environmental pollution.
As illustrated in the image above, a single large droplet of 400 micrometers divides into eight smaller droplets when it becomes a medium-sized droplet of 200 micrometers. Shrinking further to 100 micrometers results in sixty-four tiny droplets, and reducing to 50 micrometers creates five hundred twelve droplets.
The droplet size is closely linked to droplet coverage density and the volume of liquid sprayed. As droplet size decreases, the number of droplets grows exponentially, increasing the likelihood of pesticides hitting the intended target and ensuring a more uniform coverage.
To illustrate the impact of droplet size on drone spraying efficiency, consider the following examples:
During pesticide application, larger droplets tend to settle quickly, making them less prone to wind drift or evaporation. However, they distribute unevenly, adhere poorly, and are easily lost due to bouncing or rolling, diminishing pesticide efficacy and contributing to environmental pollution.
Smaller droplets, on the other hand, are more susceptible to drift caused by air currents, potentially harming neighboring crops. Yet, they provide superior coverage density and uniformity on the surfaces of crop leaves compared to larger droplets. Their strong adhesive properties make them less prone to loss, ensuring higher pesticide utilization.
Additionally, smaller droplets exhibit better penetration capabilities, allowing them to infiltrate deep into the canopy of plants and settle on the undersides of leaves where larger droplets struggle to reach. For agents with poor conductivity in leaf tissues, finer droplets can enhance biological reactions.
Thus, for pesticides requiring contact action, smaller droplets yield better control outcomes. However, finding the optimal droplet size—balancing sedimentation and coverage—is key to maximizing effectiveness. This involves understanding how to control droplet size.
Nozzle Control: Pressure Nozzles vs. Centrifugal Nozzles
During drone spraying operations, the liquid pesticide is atomized by the drone’s atomizing section to create fine droplets. In this process, the nozzle serves as the core component of pesticide atomization.
Presently, there are two primary types of drone nozzles: pressure nozzles and centrifugal nozzles. Let us compare the atomization principles of these two types and their respective advantages and disadvantages.
In general, centrifugal nozzles excel at controlling droplet size and offer better atomization, which is more beneficial for pesticide spraying.
Biological Optimal Droplet Size and Pesticide Control Efficiency
As previously mentioned, finding the right balance in droplet size is essential for achieving the best results. How do we identify this balance?
Research indicates that different biological targets capture a range of droplet sizes, with the highest number of droplets captured and the best control effect achieved within the optimal droplet size range. This concept is known as the "biological optimal droplet size theory."
Using this theory, droplet size and spraying techniques can be tailored according to pest characteristics, significantly reducing pesticide application amounts while enhancing control efficacy.
For different biological targets, the optimal droplet size range varies depending on the type of pesticide used to control pests, as shown in the table below:
This means that droplets that are either too large or too small are not conducive to pest and disease control. Only when droplet size and quantity reach the ideal combination can the best control effect be achieved.
Of course, the optimal spray droplet size is influenced by many factors. For the same pest, different pesticides, targets, chemical concentrations, and even different pest stages result in varying optimal spray droplet sizes for pesticides. Variable spraying based on optimal spray droplet size represents one of the major challenges in precision dispensing technology.
Solution – Develop Precision and Controllable Variable Droplet Size Nozzles
To improve pesticide utilization and control efficiency, reduce resource waste, and minimize environmental pollution, variable spraying technology related to aviation applications is a hot topic and a key area of research in the industry. While current focus in the industry is on changing spray flow rates, the effect of these changes on droplet size remains largely unexplored.
In fact, integrating variable spraying with variable droplet size spraying to uncover their intrinsic relationship and developing a precise and controllable variable droplet size spray system is the path to solving the problem of precise pesticide application.
At present, in terms of variable spraying technology, the P20 ultra-low-volume high-speed centrifugal atomizing nozzle developed by Feifei can atomize pesticides into droplets smaller than 100 micrometers, precisely controlling nozzle spray volume, speed, and width based on different wind speeds and flight speeds.
Specifically, the spray droplet size of the P20 centrifugal nozzle can be continuously adjusted between 90 and 120 micrometers, meaning droplet diameter can be precisely controlled to meet the operational needs of different crop pests and diseases, thus achieving excellent pesticide application effects. Achieving dual-precision control over spray flow rate and droplet size represents a major breakthrough in aerospace application technology.
In summary, we have primarily analyzed the impact of droplet size on pesticide control efficacy. It is evident that for pesticides with contact toxicity, smaller droplet control is more effective; for different pests, the optimal droplet size range varies, placing higher demands on precise droplet size control and variable adjustment.
In today's agricultural drone market, variable spray systems using centrifugal nozzles are favored. The continuous enhancement of dual-precision control capabilities over spray flow rate and droplet size will undoubtedly become the direction of development for precision agricultural aviation application technology.
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