At present, there are three main methods for crop plant protection and control operations in China—manual spraying, ground-powered mechanical spraying, and aerial spraying. The industry and the scientific research community have paid little research on the distribution law of aerosol spray deposition on agricultural drones, and there is still no objective comparison between the new air spray method and the traditional spray method judge.
Today, we will compare the effects and benefits of the two spray methods through experiments and data, hoping to provide objective and reliable data and theoretical basis for the industry to choose the plant protection operation mode.
We used two types of drones and knapsack sprayers to spray pesticides on rice fields. The agricultural drones were sprayed at the lower and higher flight heights, respectively, at slower and faster flight speeds. Manual spraying was carried out in the usual way.
According to the effective spray width of the drone, we selected the experimental field with a length × width of about 60m × 12m for spraying experiments, and set a droplet collection point every 1 meter in the collection area (Fig. 3), where each collection point is A droplet collecting card is arranged at the upper, middle and lower parts of the rice to collect the droplets.
We scan the collected droplet collection cards one by one, and then use the image processing software to process and analyze the scanned images, and obtain the droplet coverage, coverage density and deposition amount per unit area under different aviation spraying parameters.
In order to characterize the uniformity and penetration of droplet deposition between the collection points in the test, we measured the coefficient of variation (CV) of the droplet deposition on each of the different collection points in the effective spray zone of the aircraft. The uniformity of deposition of droplets is measured by the coefficient of variation (CV) of droplet deposition on the upper, middle and lower layers of each collection point in the effective spray zone of the aircraft. The smaller the coefficient of variation, the droplet deposition. The more uniform, the better the penetration.
In the above formula, S is the standard deviation of the sample collected by the same group. Xi is the deposition amount per unit area of each collection point, μl*cm-2; X is the average droplet amount of each set of test points, and n is the collection of each group. Click on the number.
results and analysis–
The average droplet deposition amount of the spray test droplets on the upper, middle and lower layers of rice plants is shown in Table 3. Combined with the dredging operation parameters and the droplet deposition results in Table 4, the following conclusions can be analyzed.
The amount of aerosol spray applied to rice plants is affected by the operating speed parameters of the drone. Under other conditions, the slower the operation speed of the drone, the lower the working height, and the more the droplets are deposited between the plants.
In terms of artificial application, the amount of droplet deposition in the upper layer of rice plants is much higher than that in the middle and lower layers, and only 3.27% of the liquid amount reaches the bottom of the plant. In the air application, 10%~30% of the liquid medicine can reach the bottom of the plant, which is much higher than the manual spraying operation mode.
Analysis of uniformity of droplet deposition
The experimental results show that the height of the aeronautical spraying operation has a significant influence on the uniformity of the droplet deposition. When the working height is high, the droplet deposition is even better. At the same working height, the different working speeds have little effect on the uniformity of droplet deposition.
The uniformity of droplet deposition by artificial application is the worst. This is mainly because the manual spraying operation is difficult to ensure the consistency of the operation route. Whether in the upper, middle or lower layers of rice plants, the uniformity of droplet deposition of artificial application is worse than that of aerial spraying.
It is worth noting that because the wind field under the rotor of the UAV can increase the penetration of the droplets between the crop plants, the wind field strength of different types of UAV rotors is different, and the operating parameters (flight altitude, flight speed) are opposite to the droplets. The uniformity of deposition has different effects.
Penetration analysis of droplet deposition
Similarly, by analyzing the average droplet deposition amount deposited on the upper, middle and lower layers of rice plants, it can be seen that the flight speed of the drone has a significant influence on the droplet penetration. The specific performance is that when the speed is slow, the droplet penetration is better. This is because when the working speed is fast, the liquid medicine becomes a tiny mist after being atomized by the nozzle, and under the action of the airflow in the horizontal direction, it mainly deposits in the canopy of the rice plant in the form of falling; When it is slow, under the action of the swirling airflow under the rotor of the drone, a part of the tiny droplets will be deposited in the lower layer of the rice plant.
For artificial application, the sediment permeability of the droplets between rice plants was the worst, at 10.42%. Artificial application is used, because most of the liquid is deposited in the canopy of the crop because there is no swirling airflow like the drone.
Benefit analysis of different spraying methods
Table 4 shows the comparison results of the efficiency and benefit of pesticide application and manual application of agricultural drones. In the actual operation, the agricultural drone is sprayed with high-concentration liquid medicine, the dosage is 15~18kg·hm-2, the labor cost is 135 yuan·hm-2, and the dosage of artificial spraying liquid and water The quantities are 0.30~0.45 and 375~450kg·hm-2, respectively, and the labor costs are 180~225 yuan·hm-2. By comparison, the working efficiency of general UAV application is about 10 times that of manual application, and the cost is low and the benefit is high.
In general, traditional manual application methods are labor intensive, inefficient, and time consuming. In the case of sudden and explosive pests and diseases, it will be difficult to meet the control requirements and cause serious losses, and the pesticides are prone to poisoning incidents. .
The large-scale mechanical spraying method on the ground has high operation cost, low effective utilization rate of the medicament, and difficulty in working in the field, which is easy to damage the crop and soil physical structure and affect the later growth of the crop.
The air application operation speed is fast, the cost is low, and the problem of ground machinery operation in the rice growth process can be solved. It has gradually become the preferred spraying operation method in people’s minds, and will be more and more widely used.