In the process of agricultural modernization, UAV fertilization, with its advantages of high efficiency and precision, is gradually becoming a powerful assistant for farmers. However, to fully leverage the effectiveness of UAV fertilization, choosing the right fertilizer is of utmost importance. From physical properties to chemical characteristics and safety considerations, each aspect plays a decisive role in the fertilization effect.
1.1 Granular Fertilizers
1.Uniformity of Granule Size:When UAVs spread granular fertilizers in the air, uniform granule size is a prerequisite for ensuring precise fertilization. Just imagine, if the fertilizer granules vary in size, the smaller ones will be like light feathers, being blown further away by the wind, while the larger ones will be like heavy stones, concentrating in the area near the UAV. This will undoubtedly lead to uneven nutrient distribution in the fertilized area, seriously affecting crop growth. Taking compound fertilizers as an example, when used for UAV fertilization, the ideal granule diameter should be strictly controlled within the range of 1 – 4 millimeters. This narrow diameter deviation range helps to ensure that the granules are evenly distributed during the spreading process, so that each area of the farmland can receive an appropriate amount of fertilizer.
2. Granule Fluidity:Fertilizer granules need to have good fluidity to ensure smooth passage through the spreading device of the UAV. Granules with good fluidity can move smoothly in the hopper and be discharged evenly from the spreading port. If the fluidity of the granules is poor, blockages may occur, disrupting the continuity of the fertilization operation. Some granular fertilizers with specially treated, smooth surfaces are more suitable for UAV spreading. For instance, certain coated slow – release fertilizers, whose coating process can not only control the release of nutrients but also enhance the fluidity of the granules. The smooth coating reduces the friction between the granules, allowing them to flow freely in the spreading system of the UAV.
1.2 Liquid Fertilizers
1. Solubility:For liquid fertilizers, good solubility is crucial. The spray device of the UAV needs to atomize the fertilizer solution evenly. If the fertilizer has poor solubility, crystals or precipitates may form at the nozzle, clogging it. For example, some foliar fertilizers containing trace elements should be fully dissolved when prepared into a solution to ensure smooth spraying. At the same time, the dissolved fertilizer solution should have good stability to avoid component separation during storage or spraying. Once the solution is unstable, the nutrients in the fertilizer may separate, resulting in inconsistent nutrient content in the sprayed liquid, which will affect the growth of crops.
2. Viscosity:The viscosity of liquid fertilizers also needs to be appropriate. A fertilizer solution with too high viscosity is not conducive to atomization. It may cause the droplets ejected from the nozzle to be too large, unable to adhere evenly to the crop surface. Conversely, if the viscosity is too low, the droplets may be too fine and easily blown away by the wind. Generally, the viscosity of liquid fertilizers suitable for UAV spraying should be close to or slightly higher than that of water. This ensures that the nozzle can atomize the fertilizer solution into droplets of an appropriate size (usually between 50 – 200 microns), which is beneficial for crop absorption. Droplets of this size can better adhere to the surface of crops and are less likely to be lost due to external factors such as wind.
2. Chemical Properties
2.1 Nutrient Content and Ratio
1. Meeting Crop Requirements:The nutrient content and ratio of fertilizers should match the needs of crops. Different crops have different demands for major nutrients such as nitrogen, phosphorus, potassium, and various trace elements at different growth stages. For example, during the jointing stage of corn, more nitrogen fertilizer is required to promote stem growth. The fertilizer used for UAV fertilization should be configured according to this need to ensure that the nitrogen content in the fertilizer can meet the growth requirements of corn. Moreover, the balance between nutrients should also be considered. An excessive or insufficient amount of a certain nutrient may affect the normal growth of crops. If there is too much nitrogen and too little phosphorus, the growth of the root system may be inhibited, while too much potassium may lead to problems such as poor fruit quality.
2. Nutrient Release Rate:For some compound fertilizers containing multiple nutrients, the nutrient release rate is also very important. Especially when using UAVs for fertilization, it is necessary to select the appropriate compound fertilizer according to the crop growth cycle and fertilization frequency. For fruit trees with a long growth cycle, slow – release compound fertilizers may be needed. By precisely spreading the fertilizer around the roots of fruit trees using a UAV, the nutrients can be slowly released over a long period, continuously providing nutrients for the fruit trees. This not only meets the long – term nutrient needs of fruit trees but also reduces the frequency of fertilization, saving labor and time costs.
2.2 Acidity
The acidity – alkalinity of fertilizers affects their effectiveness in the soil and their adaptability to crops. Most crops are suitable for growing in a soil environment close to neutral (pH value between 6.0 – 7.5). The acidity – alkalinity of fertilizers used for UAV fertilization should match the soil and crops. For example, if acidic fertilizers are continuously applied to acidic soils, it may lead to increased soil acidification, affecting soil microbial activity and crop nutrient absorption. Therefore, when fertilizing acidic soils, some slightly alkaline or neutral fertilizers can be selected and precisely applied through UAVs to adjust the soil acidity – alkalinity and promote crop growth. This can help to improve the soil environment, making it more suitable for the growth of crops, and at the same time, improve the utilization rate of fertilizers.
3. Safe for UAV
Fertilizers should not corrode the equipment of UAVs. The materials of UAVs mainly include metals (such as aluminum alloys), plastics, and electronic components. Some fertilizers with strong acidity or alkalinity may corrode the metal parts or damage the electronic components of UAVs. For example, fertilizers containing a high concentration of chloride ions may corrode the metal shell and internal circuits of UAVs. Therefore, when selecting fertilizers, their chemical properties should be considered to avoid using fertilizers that may damage UAV equipment. This can ensure the normal operation and service life of UAVs, reducing the cost of equipment maintenance and replacement.
Fertilizers should be safe for operators and the environment. During the UAV fertilization process, fertilizers may drift into the surrounding environment. Therefore, fertilizers with high toxicity or pungent odors should be avoided. For example, some fertilizers containing high concentrations of heavy metals or harmful chemicals not only pose a threat to the health of operators but also may pollute soil, water bodies, and air. At the same time, fertilizers should also meet safety standards during storage and transportation to prevent safety accidents such as leakage. This is not only responsible for the health of farmers and the ecological environment but also helps to promote the sustainable development of agriculture.