Vadose‐zone process regimes for salt‐balance management of salt‐affected soils

Salt‐affected soils have been studied for decades, yet reclamation remains inconsistent because management is still largely organized around techniques rather than the vadose‐zone processes that determine their success or failure. This review argues that effective salinity management requires a shift from technology‐centered prescriptions to process‐regime diagnosis coupled with root‐zone salt‐balance accounting. We synthesize four interacting vadose‐zone regimes—leaching‐dominated, evaporation‐dominated, groundwater‐coupled, and saline‐sodic structural‐collapse systems—and evaluate the dominant fluxes, diagnostic indicators, failure mechanisms, management options, and strength of supporting evidence for each. The synthesis shows that drainage and managed leaching are strongly supported where boundary conditions permit sustained salt export, whereas calcium amendments are essential in sodic systems to preserve hydraulic function during desalination. By contrast, mulching, drip irrigation, halophyte‐based utilization, and digital twins are context‐dependent or remain emerging approaches requiring further field validation. We further identify the preferential‐flow paradox, whereby rapid flow pathways may enhance drainage while reducing salt‐contact efficiency, demonstrating that reclamation success should be evaluated by changes in profile salt storage and salt mass export rather than drainage volume alone. Integrating groundwater dynamics, evaporation fronts, electrolyte dilution, monitoring uncertainty, and wetland connectivity, this review provides a unified framework linking diagnosis, evidence synthesis, management design, and adaptive verification. The proposed process‐regime perspective offers a transferable foundation for managing salt‐affected soils under climate change, groundwater nonstationarity, and increasing pressure on water and land resources.