Synergistic Effects of Subsurface Drainage and Root-Zone Oxygenation on Wheat Yield and Ion Homeostasis in Saline Soils with Shallow Groundwater

). The synergy index of 1.40 (95% CI: 1.28-1.52) indicated that combined effects exceeded the sum of individual treatments by 40%. Methane emissions declined by 62%, and the system achieved a 2.9-year payback period with a benefit-cost ratio of 4.08. These results establish drainage as a physical prerequisite for effective oxygenation, providing a mechanistic explanation for the variable performance of aeration systems reported in previous studies.