# Research Progress Regarding the Precision of Dosing and Distribution Devices for Fertilizers
## 2 Current Status of Research on Precision Fertilizer Dischargers
### Research Status of Disc Fertilizer Discharge  
The working principle of disc fertilizer dischargers is as follows: fertilizer particles drop from the fertilizer box onto the fertilizer spreading disc. The fertilizer blades rotate around the axis, striking the fertilizer as they rotate at a certain speed, pushing the fertilizer toward the edge of the disc. The amount of fertilizer discharged can be adjusted by changing the rotation speed of the turntable and adjusting the height of the door. Finally, under the action of centrifugal force, the fertilizer is thrown out at a consistent speed. The  
Figure 21: Structural diagram of staggered gear fertilizer discharger. Note: 1. left-hand rotation groove wheel; 2. right-hand rotation groove wheel; 3. shell; 4. transmission gear; 5. fertilizer discharge port. structure of disc fertilizer dischargers includes a fertilizer-spreading disc, along with two or more fertilizer-spreading blades, as depicted in Figure 22. This fertilizer discharger is primarily suitable for granular and powdered fertilizers, offering good looseness and fluidity. It features a simple structure, high operational efficiency, uniform fertilization, and minimal risk of fertilizer accumulation. Although widely utilized, it encounters challenges related to high resistance due to its structure [35]. The work of international researchers focuses on studying the factors affecting the average spreading radius, the structure and working parameters of the fertilizer spreading disk, and the impact of the fertilizer discharge angle on the fertilizer discharge performance through simulation, bench testing, or developing new designs for disc fertilizer dischargers. They consistently optimize the parameters of fertilizer spreading discs to enhance the precision of fertilizer distribution. [PERSON] et al. [36] conducted a bench test employing a four-factor experimental model to investigate the impact of parameter settings on the average radius of the disc fertilizer discharger. They analyzed the movement of three chemical fertilizers (urea, calcium ammonium nitrate, and ammonium sulfate) in discs with two different blade angles (as shown in Figure 23). Model variance analysis revealed that fertilizer type, blade configuration, and disc angular velocity collectively contributed to 91.74% of the variance in the average diffusion radius. Furthermore, linear multiple regression analysis indicated that fertilizer dust fraction and disc angular velocity had an overall impact of 82.72% on the variance of the average diffusion radius. Notably, among the research findings, the negative correlation between fertilizer dust fraction and blade angular velocity was as high as 72.77%, offering valuable insights for future research endeavors. To enhance the uniformity and efficiency of fertilization, [PERSON] et al. [37] devised a tilt-axis fertilizer discharger, depicted in Figure 24. Field trials revealed that the rotation frequency of the disc exerts the most significant impact on the uneven distribution of fertilizers along the fertilization line in the tilt-axis fertilizer discharger. Adjusting the disc tilt angle and rotation frequency enables effective control of the fertilizer application width. Experimental findings demonstrate that increasing the rotation frequency from 600 to 800 rpm extends the effective fertilization range to 10.5 m while raising the inclination angle to 20 degrees expands the fertilizer spread range to 24 m. The tool exhibits an exponential upward trend in each operational mode, providing a foundation for selecting optimal parameters and operational techniques for fertilizer dischargers. Figure 22: Structural diagram of disc fertilizer discharger: (**a**) top view; (**b**) left view. Note: 1. fertilizer spreading disc; 2. fertilizer spreading blade. To address the issue of insufficient fertilizer uniformity during high-speed rotation of centrifugal fertilizers discharges, [PERSON] et al.