A cyclic ecological strategy for ameliorating saline-alkali soils using biochar and Cenchrus fungigraminus (JUJUNCAO)

This study proposes an innovative cyclical strategy for the remediation of marginal saline-alkali soils by converting ecological plants into biochar (BCN). Acid-etched BCN exhibited increased oxygen-containing functional groups and a larger surface area, leading to superior Na ⁺ adsorption and an improved growth environment for Cenchrus fungigraminus (JUJUNCAO). Soil application of 1.5-2% BCN enhanced the saline-alkali resistance of JUJUNCAO by stimulating its intrinsic antioxidant system; specifically, SOD activity increased by 454%, while proline and soluble sugar contents rose by 36.7% and 80.1%, respectively. Furthermore, the synergy between BCN and plant growth improved soil fertility, increasing organic matter by 73.2% and alkali-hydrolyzed nitrogen by 114.2% while reducing water-soluble salt, electrical conductivity, and alkalinity by 84.1%, 55.3%, and 42.6%, respectively. Notably, the yield of Acid-modified Biochar (A-BCN) derived from JUJUNCAO grown in this improved soil increased from 18.9% to 35%. This second-generation biochar featured an optimized H/N ratio, which intensified the ion exchange between H⁺ on the biochar surface and Na⁺ in the soil. This self-reinforcing mechanism achieves a virtuous cycle for the ecological economy through a domino-like improvement effect.