In order to solve the traditional single-spiral fertilizer discharger issue of the fluctuation of fertilizer-discharge flow and the problem of precise fertilizer discharge, the innovative design of a cantilevered oblique placement of a fertilizer-discharging spiral structure in the form of an inclined spiral fertilizer discharger was realized, in which, through the fertilizer spiral’s full end-filled extrusion, uniform delivery of the discharge was achieved. Discrete element simulation was used to compare the fertilizer-discharge characteristics of inclined and traditional single-spiral fertilizer dischargers, and the results proved that the inclined spiral fertilizer discharger effectively reduced the fluctuation of the fertilizer-discharge flow rate. Through a theoretical analysis preformed to determine the theoretical fertilizer discharge and the main parameters affecting the uniformity of fertilizer discharge, we identified the tilting angle of the fertilizer discharger (θ) and the distance from the termination spiral blade to the fertilizer outlet (l). A two-factor, five-level quadratic generalized rotary combination experiment was conducted with two parameters (θ and l) as the experiment factors and the variation coefficient of fertilizer-discharge uniformity (σ) as the experiment indicator. The experimental results showed that for σ, θ was a highly significant effect, l was a significant effect, and σ was less than 8.5%; when θ was 35.02° and l was 16.87 mm, the fertilizer-discharge performance was better. A bench experiment was used to compare the traditional and inclined spiral fertilizer dischargers, and the results showed that the relative error of the variation coefficient between the bench and the simulation experiment under this combination was 2.28%. And compared with the traditional spiral fertilizer discharger’s σ average increase of 80.79%, the effect of fertilizer discharge was better than the traditional spiral fertilizer discharger. A fertilizer application controller was developed, and the bench performance was tested based on the measured fertilizer-discharge flow rate fitting equation of this combined inclined spiral fertilizer discharger. The results show that the electronically controlled inclined spiral fertilizer discharger has an average deviation of 3.12% from the preset value, which can be used to regulate the flow of fertilizer discharged through the fertilizer controller to realize precise fertilizer application, and this study can provide a reference for the optimal design of the spiral fertilizer discharger.

In order to solve the problem of uniform and precise fertilizer discharge, based on experimental analysis of the uneven nature of single-screw fertilizer discharge, a double arc groove screw fertilizer discharger was designed based on the principle of the half-cycle superposition of the fertilizer discharge curve. The fertilizer discharge amount and the instantaneous fertilizer discharge characteristics of the double arc groove screw fertilizer discharger were theoretically analyzed, and the factors affecting the fertilizer discharge uniformity of the double arc groove screw fertilizer discharger were obtained, taking the pitch S, arc groove radius R_p and center distance as the test factors. Using the uniformity variation coefficient and fertilization accuracy as test indexes, the experimental indicators were evaluated through a quadratic universal rotation combination design experiment with three factors and five levels. The optimal parameters were pitch S = 35 mm, arc groove radius R_p = 17 mm and center distance a = 40 mm. The fertilizer discharger was produced based on the optimal parameter combination, and a bench verification test and a comparative test were carried out. The test results show that the uniformity variation coefficient of the bench test and the relative error between the fertilization accuracy and the simulation test are 5.60% and 5.52%, respectively, and there is little difference between them, which verifies the correctness of the simulation. The comparative test results show that the uniformity variation coefficient of the optimized double arc groove screw fertilizer discharger is 7.16%, the fertilization accuracy is 3.44% and the fitting curve equation R² of fertilizer discharge flow is 0.998, all of which are significantly better than in the single-screw fertilizer discharger. We developed an electronic fertilizer discharge controller and conducted bench verification tests on it. The test results show that the average deviation between the measured fertilizer discharge capacity and the preset value of the double arc groove screw fertilizer discharger based on our self-developed controller is 2.78%. This fertilizer discharge device can precisely control fertilizer discharge, effectively solving the problem of uneven fertilizer discharge in single-screw fertilizer dischargers.

In order to solve the problems of existing spiral fertilizer apparatuses, such as the variation in cavity filling rate with rotational speed, fluctuation of fertilizer discharge flow, and inability to discharge fertilizer precisely, a triple-head gradually reducing spiral fertilizer apparatus is designed, which gradually compresses fertilizer particles through the triple-head reducing fertilizer spiral structure to achieve complete cavity filling and uniform fertilizer discharge. The main factors that affect the particle motion state and the structural size of the spiral fertilizer through theoretical analysis are determined, and its theoretical fertilizer discharge amount and rotational speed are calculated. Using EDEM (Discrete Element Method Software 2022) to establish a simulation model of a single-head gradually reducing fertilizer apparatus, the spiral lead reduction percentage x₁, spiral diameter reduction percentage x₂, and rotational speed x₃ are determined as experimental factors, and the filling rate μ and spiral torque Y_average are used as experimental indicators to conduct a simulation study on the secondary universal rotation combination design experiment. The results show that when the rotational speed is 95 r/min, the spiral lead reduction percentage is 60.00~73.21%, the spiral diameter reduction percentage is 86.55~97.05%, the filling rate μ is greater than 95%, and the spiral torque Y_average is less than 16 N·m. In order to further improve the uniformity of fertilizer discharge and ensure the controllable accuracy of fertilizer discharge, comparative verification experiments are conducted on single-, double-, and triple-head gradually reducing spiral fertilizer discharge devices and ordinary spiral fertilizer discharge devices. The results show that the precision of the gradually reducing spiral fertilizer apparatus is better than that of the ordinary spiral fertilizer apparatus. Moreover, it is determined that the three-head style performed best. The triple-head gradually reducing spiral fertilizer apparatus is also validated by randomly adjusting six rotational speeds. The experiment results show that the average deviation of the fertilizer discharge flow rate of the fertilizer apparatus from the preset value is 3.16%. The two have a minor deviation, and the fertilizer precision is high. Precise control of the amount of fertilizer discharged can be achieved by adjusting the rotational speed, and the research can provide a specific reference for the improved design and precise control of the spiral fertilizer apparatus.