Electron-irradiated superabsorbent polymers enhance soil water retention, ion homeostasis, and yield resilience of wheat across a salinity gradient

Abstract

Soil salinity restricts wheat productivity by reducing water availability, disrupting ion homeostasis, and impairing physiological and reproductive processes. Superabsorbent polymers can improve soil water retention, but the agronomic value of electron-irradiated SAPs relative to conventional commercial polymers remains insufficiently characterized. This study evaluated whether an electron-irradiated SAP could improve wheat salt tolerance through coordinated effects on soil water dynamics, plant ion balance, physiological performance, and grain production. A greenhouse pot experiment was conducted using wheat ( Triticum aestivum L. cv. C-306) exposed to five NaCl-induced salinity levels of 1, 3, 5, 7, and 9 dS m⁻¹. An electron-irradiated SAP and commercial Aquasorb were incorporated into the soil at 1, 2, or 3 g SAP kg⁻¹ dry soil, equivalent to 0.1%, 0.2%, and 0.3% (w/w), respectively, and were compared with SAP-free controls. Increasing salinity reduced polymer swelling, soil water availability, plant water status, chlorophyll content, biomass accumulation, and yield while increasing tissue Na⁺ accumulation. Both polymers alleviated these effects, but the electron-irradiated SAP generally produced stronger responses, particularly at 1–2 g kg⁻¹. At 9 dS m⁻¹, the best-performing irradiated-SAP treatments increased available soil water from approximately 0.05 to 0.09 g g⁻¹, reduced tissue Na⁺ from approximately 160 to 110 mg kg⁻¹, increased relative water content from approximately 50% to 70%, and increased seed yield from approximately 22 to 60 g plant⁻¹ compared with the corresponding SAP-free control. The irradiated SAP also maintained higher K⁺, Ca²⁺, and Mg²⁺ concentrations, chlorophyll status, antioxidant activity, biomass, and harvest index. Aquasorb produced intermediate improvements. Positive associations among soil water availability, plant hydration, ion balance, and yield supported an integrated soil–plant response pathway. Electron-irradiated SAPs improved wheat performance under salinity through a linked mechanism involving greater soil water availability, reduced Na⁺ accumulation, improved essential-cation balance, and sustained physiological activity. Application rates of 1–2 g kg⁻¹ provided the most consistent benefits under severe salinity. These findings identify electron-irradiated SAPs as promising soil conditioners for saline agriculture, although multi-season field trials are required to verify their agronomic effectiveness, persistence, and environmental safety.