A biodegradable chitosan-CMC-silk fibroin hydrogel enhances soil water retention and wheat growth in saline-alkali soil.

Enhancing water retention and crop productivity in widespread, challenging saline-alkali soils necessitates sustainable amendment strategies. This study reports the development and evaluation of a novel biodegradable hydrogel synthesized from natural polymers-chitosan (CS) and sodium carboxymethyl cellulose (CMC)-utilizing silk fibroin (SF) self-assembly for physical crosslinking, thereby avoiding toxic chemical agents. The resulting CS-CMC-SF hydrogel possessed a hierarchical porous structure (BET surface area ~ 163 m/g), exhibited high equilibrium water absorbency (130-144 g/g in deionized water), demonstrated favorable swelling stability under relevant pH and salinity conditions, possessed thermal stability up to approximately 200 °C, and showed ready biodegradability (78 % weight loss in 14 days soil burial). Application of this hydrogel at 0.5 % (w/w) to saline-alkali soil significantly increased its maximum water holding capacity by 103 % and markedly reduced the rate of water evaporation compared to unamended soil. Consequently, incorporating 0.1 % (w/w) hydrogel into the saline-alkali soil significantly promoted early wheat seedling growth, enhancing root length (~+38 %), leaf length (+20-43 %, variety dependent), biomass accumulation (+24-71 %), and plant water status under stress conditions. These findings highlight the potential of this biodegradable, natural polymer-based hydrogel, prepared via a green physical crosslinking method, as an effective soil amendment strategy to improve water resource utilization and enhance crop resilience in challenging saline-alkali agricultural systems.