Abstract
Soil degradation caused by soil salinization is an important factor affecting global food security. The soda saline–alkali soils in the Songnen Plain suffer from poor soil structure, hard topsoil and alkalized horizons, and high pH and Na⁺ concentrations, which pose a major threat to sustainable agricultural development. However, the development of demand-adapted agricultural machinery and agronomic technologies integrating physical and chemical amelioration remains a challenge for soda saline–alkali soil improvement under rain-fed dryland conditions. Based on the water solubility of aluminum sulfate, this study integrated novel equipment and technologies for efficient, engineering-oriented amelioration of soda saline–alkali soils. Experiment analysis of aluminum sulfate application rate experiments showed that the optimal amelioration effect was achieved at an ameliorant dosage of 0.6% of soil dry weight, with a pH reduction of 0.81 units. By means of installing liquid ameliorant spraying components on the base subsoiling machine, it was developed that integrated equipment for simultaneous subsoiling and ameliorant application across the entire plow layer was developed. Verification tests demonstrated that the soil disturbance coefficient, soil loosening degree, and coefficient of variation for liquid application uniformity among rows were 53.75%, 13.50%, and 4.83%, respectively; these operational performance indicators met the requirements of relevant industry standards. Comparisons of soil physicochemical properties under different amelioration treatments revealed that subsoiling combined with ameliorant spraying (SAS) outperformed subsoiling alone (S), surface ameliorant application (A), and the control (CK). Relative to CK, the SAS treatment increased soil water infiltration rate (WIR) by an average of 63.11%, reduced bulk density (BD) by 0.14 g/cm³, decreased pH by 0.86 units, and lowered soil salt content (SC) by 0.71 g/kg. Three-year field alfalfa cultivation experiments indicated that SAS increased alfalfa emergence rate, dry matter yield, and overwintering rate by 20.60%, 26.45%, and 20.29%, respectively, relative to CK. This study proposes an implementation strategy for integrated physical and chemical amelioration equipment and technologies for soda saline–alkali soils based on the SAS approach, which provides equipment, technical, and engineering application references for improving soil health, boosting crop yield, and promoting the efficient utilization of rain-fed soda saline–alkali land.