To elucidate the mechanism by which soil disturbance affects tillage performance during subsoiling remediation of northeastern primary sodic saline–alkali soil, this study established a mathematical prediction model linking subsoiler configuration parameters with draft force and soil porosity based on the soil dynamic equation and the fourth strength theory. Discrete element simulation and field experiments demonstrated the model’s accuracy in predicting draft force and soil looseness (error < 5%). Among three configuration patterns evaluated, the “W”-type arrangement was selected for further simulation testing and predictive analysis through parameter adjustment. The simulation results aligned with the prediction results. Particle flow analysis revealed a quadratic relationship between subsoiler spacing variation, draft force, and soil looseness. At the particle scale, soil particle movement patterns were found to govern macroscopic effects, where soil clogging and repeated disturbances emerged as primary drivers of nonlinear variations in draft force and soil porosity. Finally, field experiments and simulations were performed using the parameter combinations predicted by the mathematical model, confirming the accuracy of these parameters. Through a tripartite validation approach combining mathematical modeling, DEM simulation, and field trials, this study systematically elucidates the complete mechanism whereby subsoiler arrangement parameters influence the tillage performance of sodic saline–alkali soil via soil–tool interactions, providing theoretical foundations for optimizing subsoiling equipment design and reducing energy consumption in saline–alkali land cultivation.

Saline-alkali soil has the characteristics of high density, high firmness and poor permeability. Aiming at the problems of shallow subsoiling depth, large subsoiling specific resistance and small soil bulkiness in subsoiling operation in saline-alkali soil, this paper establishes a mathematical model of the specific resistance of a broken line subsoiler and uses genetic algorithm and the discrete element method to optimize the structure design of the subsoiler. Firstly, the mathematical model was developed by analyzing the force of the subsoiler in the working process. The genetic algorithm was used to solve the problem, and three geometric models of the broken line subsoilers were fitted. Then, EDEM software was used to simulate this, and the tillage performance was evaluated with draft force, soil disturbance area, subsoiling specific resistance and soil bulkiness as the indexes and verified by field experiment. The results showed that the subsoiling specific resistance of the three broken line subsoilers was significantly lower than that of the standard subsoiler in the simulation test. Compared to the standard subsoiler, the soil disturbance area of the broken line subsoiler-B increased by 12%, the draft force decreased by 19%, the subsoiling specific resistance decreased by 26% and the bulkiness increased by 6%. The field experiment results showed that the broken line subsoiler-B reduced the traction force and improved the tillage efficiency compared to the standard subsoiler, which was consistent with the analysis results of EDEM. The broken line subsoiler can effectively enhance the quality of cultivated land.