Mitigating Salt Stress in Saline-Alkali Soils through Co-Application of Superabsorbent Carbon-Based Material and Flue Gas Desulfurization Gypsum

Shengnan ZhangYouming YangJuanxiang ZhangXiaoyan Qian^*

• Tarim University, Xinjiang, China

Flue gas desulfurization gypsum (FGD) and biochar are considered effective amendments for alleviating soil salinity stress. However, the co-application of these amendments in practice requires further investigation. This study successfully prepared a superabsorbent carbon-based material (CB) via graft polymerization and applied it in combination with FGD to investigate their effects on leaching salt ions and improving salinealkali soil. A laboratory soil column leaching experiment was conducted with six treatments: control (CK, no amendment), cotton straw biochar (BC), CB, FGD, BC+FGD, and CB+FGD.Field plot trials were further employed to evaluate the soil amendment efficacy. The results demonstrated that the co-application of the CB and FGD significantly alleviated salt stress by promoting Na⁺ leaching. During the P1 (sharp decrease) leaching phase, Na + leaching concentrations under the sole FGD and CB+FGD treatments increased by 89.08% and 90.92%, respectively, compared to CK. Co-application with FGD significantly increased the content of Ca 2+ and SO4 2 ⁻ in the soil. The CB effectively retained soil K⁺, and the Cl⁻ content after leaching was significantly lower than in CK. Field trials further confirmed that the co-application of the CB and FGD significantly reduced the contents of Na⁺, Cl⁻, and Mg 2+ while increasing the contents of Ca 2+ , K⁺, and SO4 2 ⁻. The contents of Na⁺, Cl⁻, and K⁺ increased with soil depth, indicating the migration of major salt ions towards deeper soil layers with water movement.The CB+FGD treatment significantly reduced soil TSS, electrical conductivity (EC), and SAR.In conclusion, the co-application between the CB and FGD enhances salt leaching efficiency and soil water retention capacity, exerting a positive influence on the remediation of salinealkali soils. This study provides a novel strategy for utilizing agricultural waste in saline soil management.