Lignosulfonate provides a sustainable strategy for soil acidification mitigation through dual suppression of nitrification-driven protons and active aluminum

Soil acidification driven by nitrification threaten agricultural sustainability, yet strategies to concurrently suppress proton generation and immobilize phytotoxic aluminum (Al) remain limited. This study evaluated six amendments, including silicon-calcium-magnesium compounds (SiCaMg), humic acid (HA), biochar (BC), chitosan (CH), cellulose (CE), and sodium lignosulfonate (LNa), for controlling soil acidification, Al phytotoxicity, and nitrification process. Compared to untreated control (CK), LNa increased soil pH by 0.69 units, enhanced exchangeable base cation (EBC) pool by 1.45-fold while reduced exchangeable Al 3+ by 36.1 %, outperforming SiCaMg which achieved 0.52 units rise in pH, 0.86-fold increase in EBC but 57.8 % decrease in phytotoxic Al 3+ . Notably, soil reacidification was retarded by LNa whereas accelerated by SiCaMg. Soil solid-state 27 Al nuclear magnetic resonance (NMR) analyses revealed that SiCaMg immobilized Al primarily through co-precipitation, whereas LNa and CH facilitated organic-Al complexation mediated by sulfonic and amino ligands, respectively. Notably, nitrification rate was promoted from 1.48 (CK) to1.86 mg kg −1 ·d −1 with SiCaMg, concomitant with the enrichment of ammonia-oxidizing archaea (AOA, Ca. Nitrososphaera ) and nitrite-oxidizing bacteria (NOB, Nitrospira ). Conversely, nitrification rate was strongly suppressed to 0.34 mg kg −1 ·d −1 by LNa, attributable to reductions in both AOA and NOB populations. Whereas HA and BC exerted minimal effects on soil acidity and nitrification, CE unexpectedly activated Al mobility and decoupled nitrification process despite reducing AOA/NOB abundance. We establish LNa as a uniquely dual-functional inhibitor that mitigates soil acidification through simultaneous Al immobilization and nitrification inhibition. This work advances a “source-process management” paradigm for sustainable agricultural soil remediation.