# Research Progress Regarding the Precision of Dosing and Distribution Devices for Fertilizers
## 2 Current Status of Research on Precision Fertilizer Dischargers
### Research Status of Groove Wheel Fertilizer Discharge  
The working principle of groove wheel fertilizer discharges is as follows: the groove wheel rotates around the axis, and through the movement of the groove wheel teeth, the granular fertilizer dropped from the fertilizer box is conveyed to the fertilizer discharge port and ultimately discharged onto the soil. Its structure is depicted in Figure 11[22]. This fertilizer discharger imposes stringent requirements on the physical properties of fertilizers. When handling wet granular fertilizers and powdery fertilizers, fertilizer discharge pulsations are prone to occur [23]. Fertilizers with poor fluidity can easily block the groove wheel, impeding proper operation. With its simple structure and suitability for various  
Figure 10: Schematic diagram of the overall and partial structure of the spiral double-wheel fertilizer discharger: (**a**) the overall structure of the spiral double-wheel fertilizer discharger; (**b**) shell cross-section; (**c**) fertilizer wheel chart. Note: \(a\) is the center distance, \(r\) is the inner diameter of the spiral blade, \(R_{p}\) is the height of the blade, \(b\) is the thickness of the spiral blade, \(S\) is the pitch. 1. spiral blade; 2. fertilizer inlet; 3. fertilizer discharge wheel; 4. large gear; 5. pinion; 6. inner hexagonal hole; 7. fertilizer discharge port; 8. housing. types of fertilizers, the groove wheel fertilizer discharger has rapid fertilizer discharge and is widely employed. Nonetheless, it exhibits significant variations in fertilizer discharge effects and may encounter challenges related to poor control accuracy and linearity. The research of international researchers focuses on studying the fertilizer discharge performance through discrete element simulation, conducting comparative bench testing, and developing new designs for groove wheel fertilizer dischargers. They aim to optimize the parameters of key structural components, particularly the groove wheel, in order to enhance the accuracy and uniformity of fertilizer discharge dosing. [PERSON] et al. [24] devised a spiral groove wheel fertilizer discharge device to replace the traditional straight groove wheel fertilizer discharge device. The structure of the groove wheel is depicted in Figure 12. The discrete element method was employed to test and simulate the fertilizer discharge performance. Results indicate that, under similar conditions, the spiral groove wheel demonstrates superior fertilizer discharge stability and uniformity compared to the straight groove wheel, with fertilizer particles falling at a faster rate. The relative error between the actual test results and the simulation results is less than 10%. The performance of the developed spiral groove wheel surpasses that of the traditional straight grooved wheel, thereby providing a theoretical foundation for the design of high-performance fertilizer dischargers. [PERSON] et al. [25] developed a new design for a pin-roller for variable fertilization, as depicted in Figure 13. The experiment utilized compound fertilizer N-P\({}_{2}\)O\({}_{5}\)-K\({}_{2}\)O and tested three different rotation speeds (20 rpm, 55 rpm, 90 rpm). By optimizing the structural  
Figure 11: Structural diagram of the groove wheel fertilizer discharger. Note: 1. fertilizer baffle; 2. blocking wheel; 3. backup ring; 4. groove wheel; 5. fertilizer discharge shaft; 6. fertilizer discharge tongue; 7. fertilizer discharge shell; 8. fertilizer discharge port. Figure 12: Main structural dimensions and models of the spiral groove wheel. parameters of the pins, improvements were achieved in the uniformity and quantity of fertilizer discharge while effectively preventing fertilizer blockage. The test results indicate that compared to the traditional groove wheel fertilizer discharger, the new fertilizer discharge exhibits a higher coefficient of variation in the fertilizer discharge uniformity when rotating at low speeds, reaching up to 10.36%.