Zwitterionic humic acid hydrogel with anti-polyelectrolyte effect for dual-functional saline-alkali soil remediation and maize stress alleviation

Soil salinization severely constrains agricultural productivity in arid regions. This study synthesized a novel zwitterionic superabsorbent polymer (SAP), HA-g-P(AA-co-SBMA), by grafting humic acid (HA) and [2-(methacryloyloxy) ethyl] dimethyl-(3-sulphopropyl) (SBMA) onto an acrylic acid (AA) backbone. This material exhibits both water retention and salt resistance, with water absorption rates of 2698 g g −1 in distilled water and 122 g g −1 in 0.9% NaCl solution, while maintaining stable performance across a pH range of 4–10. Pot experiments demonstrated that as a salt barrier layer, this SAP reduced soil Na⁺ content by 28–46%, significantly lowered electrical conductivity (EC) and pH, and increased maize ( Zea mays L.) germination rates by 40–161% under 0.3–1.5% NaCl stress. Molecular dynamics (MD) simulations confirm that HA and SBMA synergistically enhance hydrophilicity and Na⁺ adsorption capacity through hydrogen bonding and electrostatic interactions. Granular SAP outperforms film-based forms by avoiding the oxygen-depletion effect. This study provides a sustainable, multifunctional material solution for saline-alkali soil remediation and crop stress resistance. The reclamation of saline-alkali soils is a worldwide challenge, and some improvement methods are more difficult to implement in drought-prone areas. This research shows that the two forms of superabsorbent polymers prepared can markedly improve soil physicochemical properties. In moderately and severely saline-alkali conditions, the use of these polymers can aid maize ( Zea mays L.) seed germination and support the normal growth of maize ( Zea mays L.) seedlings. • Introduce zwitterionic monomer SBMA to enhance polymer applicability in saline-alkaline environments. • All-atom MD calculations validate humic acid and SBMA boost polymer performance synergistically. • Prepared polymers improve soil physicochemical properties via physical barrier and chemical adsorption. • This polymer promotes maize seed germination and seedling growth under moderate-severe salt stress.