Soil salinization represents a globally prevalent manifestation of soil degradation, characterized by structural deterioration and reduced saturated hydraulic conductivity (Ks). These alterations critically impair crop water uptake efficiency, ultimately threatening agricultural productivity. Despite extensive recognition of sodicity impacts, knowledge gaps persist regarding the differential mechanisms governing Ks limitation across soils with varying salinity-sodicity gradients. This investigation focuses on the Songnen Plain, a saline-sodic epicenter in Northeast China that serves as a representative model for analogous global ecosystems. We systematically identify the primary constraints and mechanistic pathways regulating Ks suppression in these degraded soils. Our analyses reveal significant inverse correlations between Ks and both salinity and sodicity parameters, with spatial patterns demonstrating elevational controls: lower-lying plains exhibited elevated sodicity and depressed Ks values, whereas Ks increased with elevation gain. Mechanistic investigations implicate exchangeable sodium accumulation on colloidal surfaces as the fundamental driver of Ks reduction through two synergistic pathways: (1) led to an increase in soil salinity and total alkalinity, and (2) colloidal dispersion disrupting aggregate stability and pore architecture. Quantitative path analysis identified soil texture and macroaggregate depletion (WSA> 0.25 mm) as dominant physical regulators, while sodicity-mediated pH shifts emerged as principal chemical constraints. Notably, Ks exhibited hysteresis in response to sodicity changes-initial sodicity increases caused aggregate breakdown with limited Ks decline, whereas subsequent sodicity elevation triggered clay dispersion and dramatic Ks collapse. These findings propose a dual intervention strategy: targeted pH reduction through mineral amendments coupled with organic management practices to enhance aggregate stability, providing a mechanistic framework for Ks restoration in sodic landscapes.