To address the problems of low efficiency, poor uniformity, and low utilization rate in conventional fertilization, this study develops a walking-type agricultural fertilization device equipped with a PID-based control system, aiming to enhance automation and precision in fertilization operations. The device integrates a stirring and crushing mechanism with an electric push-rod feeding unit. The control system is built around a Siemens S7-1214 PLC, combined with an M545D driver, stepper motor, encoder, and level sensor, enabling real-time acquisition of rotational speed and material level signals. A PID algorithm is embedded in the software, which computes errors based on speed feedback and performs closed-loop regulation. Parameters are tuned using the Ziegler–Nichols method. Experimental results demonstrate that, after optimizing the mechanical design and incorporating the PID algorithm, the system achieves significant improvements in both fertilization uniformity and operational efficiency, providing a reliable technical solution for modern agricultural fertilization.