## 2 Overall Structure of Fertilization and Spraying System
### Spray Structure Design  
To address the need for comprehensive spraying operations, the design requirements for the spraying mechanism were established. This mechanism is essential for applying herbicides to the entire ground before seedling emergence to create a closed layer as well as for spraying corn leaves and the ground after emergence to manage pests and diseases. The schematic diagram of the maize spraying mechanism is illustrated in Figure 8.  
In this diagram, the rear tires on both sides are concealed. The spraying mechanism consists of three primary components: the parallel four-link elevation mechanism, the three-section folding spray frame, and the flow system, which includes the medicine box, medicine pump, and spray nozzle. This design ensures effective coverage and efficient application of the spraying solution, as demonstrated in field trials where systematic spraying reduced the pest and disease incidence in corn by 85% compared to the untreated areas and improved the control effectiveness by 30% over traditional methods, thereby promoting healthy growth and enhancing the yield and quality. The lifting mechanism of the spraying system primarily utilizes an electric cylinder with suitable thrust, enabling vertical movement of the spray frame through a simple parallel four-link structure. This design allows the mechanism to adapt to the varying ground undulations and different heights of maize plants. When the spraying device is  
Figure 8: Schematic diagram of the corn spraying mechanism. 1—Electric cylinder. 2—Parallel four-link mechanism. 3—Three-stage folding spray frame. 4—Searchlight. 5—Medicine box. 6—Water pump. 7—Water hose. 8—Nozzle. Figure 7: Fertilizer support structure diagram. 1—Positioning pin. 2—Connecting spring. 3—Mounting hole. 4—Lower arm movable slide groove. 5—Limit pin. 6—Traverse scale. 7—Fastening bolt. 8—Detector bracket. working on flat ground, it can accurately maintain the spraying height to ensure the uniform spraying of pesticides. When working on undulating land, it can adjust the spraying height in a timely manner by controlling the electric cylinder through the control panel, so that the spraying frame is always maintained at a certain distance above the plants, ensuring that the pesticides continuously cover the corn plants. The three-section folding spray frame is welded with 40 mm \(\times\) 40 mm steel pipes. The steel pipes possess relatively high structural strength and corrosion resistance, ensuring that they can still maintain stability after multiple folding and unfolding operations. As shown in Figure 9, when the spray frame is unfolded, each part is fixed together with long pins to maintain a consistent extension. When folding, the fixing pins can be easily removed, allowing the frame to be folded up. The connections between each part are equipped with quick-release hinges. This design not only facilitates the disassembly and installation of the entire spraying frame, but also makes the folding process smoother in terms of operational convenience. With the help of the quick-release hinges, a single person can easily complete the operation. In addition, clear operation markings are set on the spraying frame, which greatly facilitates the correct use by users. The parallel four-bar lifting mechanism and the three-section folding spray frame in the spraying system can flexibly adjust the spraying height according to the height of the corn at different growth stages, ensuring the effective coverage of pesticides on the corn plants and the ground, reducing the possibility of pesticide drift to non-target areas, and thus reducing the potential harm to the surrounding environment and organisms. Compared with common manual sprayers or spray rod machines on the market, this design offers significant advantages in both spraying efficiency and coverage uniformity.