Ca2 + substitution synergises zeolite physisorption accelerated Na+ substitution to improve saline soils

Huang-Huai-Hai region of China is characterized by saline soils with high Na⁺ concentrations, which result from seawater intrusion and groundwater evaporation. The high mobility of Na⁺ complicates soil amendment and limits crop yields by osmotic imbalances. To address high Na⁺ challenge, we conducted a two-year field experiment in the saline soil of the Huang-Huai-Hai region, designing no conditioner (C0) as the control and three types of conditioners (2.10 × 10³ kg ha⁻¹): 100 % silica-calcium-potassium-magnesium alkaline soil conditioner (SCPM), 70 % SCPM + 30 % zeolite (SCPM + ZP), and 99 % SCPM + 1 % polyacrylamide (SCPM + PAM) to explore possible ways to reduce Na⁺. SCPM + ZP reduced Compared to C0, SCPM + ZP reduced Na⁺ by 748.92–834.79 mg kg⁻¹ through Ca²⁺ substitution and physical zeolite adsorption, lowered pH by 0.24–0.60, and alleviated salt stress. Modifications to soil colloids increased binding sites for metal ions and organic carbon, which improved soil aggregation (34.78 % increase in > 0.25 mm aggregates), reduced bulk density (15.20 %), boosted porosity (19.51 %), and raised moisture content (42.39 %). These changes were accompanied by elevated enzyme activities (e.g., alkaline phosphatase, sucrase) and greater availability of nutrients like phosphorus and organic carbon in the root-soil system. Ultimately, a 96.12 % increase in spike number led to an 84.42 % rise in winter wheat yield. The combined reduction of Na⁺, enhancement of soil properties, and yield improvement achieved with SCPM + ZP offers a practical and theoretical framework for reclaiming high-Na⁺ saline soils in Huang-Huai-Hai region.