Synergistic effects of Ca-bentonite and in-situ layered double hydroxide formation in ameliorating saline-alkali soil

Improving saline-alkali soil requires cost-efficient and stable technologies. In this study, a novel technology combining in-situ super-stable mineralization with Ca-bentonite was successfully applied to ameliorate saline-alkali soil. A simulation experiment was conducted on Ca-bentonite in solution to validate its feasibility, and in-situ mineralization using humic acid, Fe(NO₃)₃·9H₂O, and Ca-bentonite was performed to treat saline-alkali soil. Additionally, climate modeling and field experiments were employed to investigate the effects of this technology on soil physicochemical properties, crop growth, and crop yield. Under natural conditions, Ca-bentonite can transform into Na-bentonite via cation exchange with Na⁺. The results from the in-situ mineralization experiment showed that the soil pH, total content of CO₃^2- and HCO₃^-, Na⁺ content, electrical conductivity, and bulk density decreased from approximately 10.30 to below 9.00, 7.81 to 1.53 g/kg, 7.20 to 1.51 g/kg, 2741 to 552 μS/cm, and 1.63 to 1.24 g/cm³, respectively. Furthermore, the germination rate of corn increased from 0 % to 83.3 % in climate simulation experiments. Field trials conducted in Inner Mongolia and Jilin, China, further demonstrated significant improvements in soil properties. The seedling emergence rates for corn and oats significantly increased, rising from 0 % to over 85 % and 95 %, respectively. Correspondingly, crop yields reached 323 kg/hm² for corn and 182 kg/hm² for oats. Together, our study introduces a novel, cost-effective, and efficient technology to enhance crop growth by mitigating soil salinity and alkalinity. This approach provides a new perspective for alleviating salt-alkali stress and contributes to the advancement of healthy and sustainable agricultural practices.