Facile acetic acid pretreatment improves salt adsorption performance of cotton straw for regulating the microecological environment of saline-alkali soil.

Soil salinization chronically threatens sustainable development of agriculture. This study proposes and validates a facile acetic acid pretreatment to enhance salt adsorption capacity of cotton straw in soils, thereby alleviating crop salt damage. Characterization results confirmed that the pretreatment disrupted the crystalline structure, consequently increasing its specific surface area and enriching surface oxygen-containing functional groups (CO, -OH). These structural and chemical modifications significantly enhanced the Na+ adsorption capacity of straw materials. Spectroscopic analysis combined with density functional theory (DFT) calculations identified hydroxyl groups as the primary Na+ binding sites, and the adsorption process was found to be exothermic, involving the cooperative effects of pore filling and hydrogen bonding. Pot experiments demonstrated that incorporating acetic acid-pretreated straw into saline soil increased cotton germination rate by over 50% and biomass by 119%-158%, even under high salinity conditions (1.0%). This improvement was attributed to a 22.7%-70.1% reduction in subsoil salt content and enhanced soil moisture retention. Furthermore, the incorporation of pretreated straw residues significantly increased the relative abundances of key microbial taxa and reshaped both bacterial and fungal communities in the soil. A field trial further verified that the application of pretreated straw improved the soil microenvironment and promoted cotton crop growth. Overall, this study presents a cost-effective and sustainable strategy for saline soil remediation by valorizing agricultural waste into a high-performance green adsorbent.