## 1 Introduction  
Currently, fertilization is often used to increase crop yield, but the excessive application of fertilizers can easily cause crop lodging, environmental pollution, and resource waste. Excessive application can reduce crop yield [1, 2, 3]. The spiral fertilizer applicator is widely used in agricultural production, with advantages such as a simple structure, convenient installation, and adjustable fertilizer discharge. However, its fertilizer discharge accuracy is low, and its fertilizer discharge effect is poor. In recent years, scholars have conducted much research to improve the fertilization precision of spiral fertilizer applicators. [PERSON] [4] et al. designed a vertical spiral rice deep-side fertilizing device. Through simulation experiments and bench tests, it was determined that the best fertilization effect was achieved with a rotational speed of 190 r/min, a diameter of 22 mm, and a forward speed of 0.45 m/s. [PERSON] [5] et al. designed an oblique opening spiral fertilizer apparatus to improve the uniformity of fertilizer discharge through the oblique opening outlet method. Through bench tests, they determined that the precision of the oblique opening spiral fertilizer apparatus was better than that of the traditional spiral fertilizer apparatus. [PERSON] [6] et al. designed a dual-directional spiral fertilizer applicator. They conducted simulation experiments with screw diameter, rotational speed, and pitch as experimental factors, and average fertilizer discharge uniformity as an experimental indicator. The results showed that when the structural parameters were a diameter of 90.1669 mm, a pitch of 59.7407 mm, and a rotational speed of 53.8944 r/min, the average fertilizer discharge uniformity reached 92.0670%. [PERSON] [7] et al. analyzed the causes of uneven fertilizer discharge from the spiral fertilizer applicator. They optimized it to determine that at a rotational speed at 47.6 r/min, a diameter of 90 mm, and a pitch of 60 mm, the uniformity of fertilizer discharge reached 19.05%, indicating a relatively good fertilizer discharge effect. [PERSON] [8] et al. designed a non-axis spiral fertilizer delivery device, which determined, through simulation and field experiments, that with a spiral blade radius of 12.8 mm, a pitch of 24.5 mm, and a rotational speed of 319 r/min, the fertilization accuracy error and coefficient of variation in fertilizer uniformity were 1.87% and 2.52%, respectively. [PERSON] [9] et al. studied and designed a blocking wheel-type screw fertilizer distributor. Through discrete element simulation, the coefficient of variation in fertilizer uniformity was optimized to less than 20% when the diameter was 17 mm, the pitch was 45 mm, and the outlet distance was 40 mm. The correctness of the simulation experiment was demonstrated through bench tests. The above research proves that, due to the structural characteristics of the spiral fertilizer applicator, fertilizer particles cannot maintain a fixed filling coefficient in the applicator cavity, making it impossible to calculate the fertilizer discharge flow rate accurately. Therefore, this article proposes the design of a spiral-pushing fertilizer applicator to increase and fix the filling coefficient by gradually reducing the amount of fertilizer discharged in a single circle, in order to accurately calculate the fertilizer discharge flow through rotation speed and achieve precise fertilization. This article analyzes the problem of the filling coefficient in the spiral fertilizer applicator and improves the design of its spiral structure of the fertilizer applicator, thus leading to the design of a spiral-pushing fertilizer apparatus. We optimize the parameters that affect fertilizer discharge accuracy through a combination of EDEM simulation and quadratic orthogonal rotation combination design experiments. Using 3D rapid prototyping technology, a spiral-pushing fertilizer applicator was manufactured for bench verification, and an electrically controlled fertilizer discharge system was designed.