# 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
Utilizing a full-factor bench test, it is observed that the fertilizer discharge amount has a strong linear correlation with both the conical turntable speed (ranging from 15 to 45 rpm) and the fertilizer discharge opening (ranging from 5 to 25 mm). The coefficients of variation for consistency of double-row fertilizer discharge, stability of total fertilizer discharge, and uniformity of fertilizer discharge vary from 1.01%  
Figure 22.1 Structural diagram of centrifugal disc fertilizer discharger. Note: 1. blade; 2. evening outlet; 3. evening cover; 4. disc; \(\beta\) is the blade position angle. to 3.88%, 1.05% to 3.81%, and 6.64% to 15.79%, respectively. When the device is tilted at 3 degrees, the maximum coefficient of variation for the consistency of fertilizer discharge in two rows is 6.17%. These test results align with the performance standards required for side-deep fertilization in paddy fields. [PERSON] et al. [43; 44; 45] investigated the fertilizer discharge performance of the spiral cone centrifugal fertilizer discharger (depicted in Figure 29) through discrete element simulation. The quadratic regression orthogonal rotation combination tests were employed to determine the optimal structural parameters: a horizontal inclination angle of 30.4 degrees, a push plate radial deflection angle of 3.2 degrees, and a cone disk speed of 130 rpm. Combined with bench and field trials, it was found that the stability variation coefficient of fertilizer discharge does not exceed 4.57%, thus meeting the standards for compound fertilizer fertilization in rapeseed fields. In addition, in order to make breakthroughs in the precise fertilizer distribution from disc fertilizer dischargers, researchers initiated research on fertilizer dischargers that integrate a spiral fertilizer conveying device with a disc fertilizer discharger. [PERSON] et al. [46] combined a vertical spiral fertilizer discharger to develop a disc variable fertilizer discharger tailored for banana orchard fertilization, as depicted in Figure 22.2 They conducted discrete element simulation tests to determine the optimal fertilizer discharger parameters: a forward speed of 0.25 mps, a rotation period of 10 s, a central angle of 90 degrees, and a curved groove opening size of 20 mm. Field trials yielded an average fertilizer discharge qualification rate of 95.33%. The model and test errors, as well as the simulation and test errors of fertilizer discharge amount, are 11.15% and 6.68%, respectively. The fertilizer discharger demonstrates commendable operational performance. Figure 22.3 Schematic diagram of the structural parameters of the conical disc: (**a**) top view; (**b**) sectional view. Note: 1. push plate; 2. conical disc. Figure 22.4 Schematic diagram of the cross-sectional area of the fertilizer tank: (**a**) schematic diagram of filling a single fertilizer tank; (**b**) maximum and minimum cross-section of a single fertilizer tank. Note: \(L_{0}\) is the maximum effective working length of the fertilizer tank; \(\Delta L\) is the change in the effective working length of the fertilizer tank. [PERSON] et al. [47, 48] conducted a three-factor and two-level general rotation combination discrete element simulation test on a clustered, bidirectional spiral, fertilizer feeding, centrifugal conical disc fertilizer device, as illustrated in Figure 31, to simulate the process of compound fertilizer discharge. The results indicate that the order of significance of factors affecting the variation coefficient of fertilizer uniformity is as follows: bidirectional spiral speed, conical disc speed, and traveling speed. The optimal parameter combination is determined to be a bidirectional spiral speed of 5.27 rpm, a conical disc speed of 243.7 rpm, and a device travel speed of 0.66 mps. Following optimization, the average coefficient of variation of fertilizer uniformity is 17.16%. The optimization and verification test results are highly consistent.