Organic fertilization alleviates Sb toxicity in rice: Insights into Sb speciation, oxidative stress mitigation, and...

Antimony (Sb) contamination poses growing risks to rice agroecosystems, and organic fertilizers have the potential to regulate Sb toxicity. However, the process and mechanism are not well understood. Here, we established a factorial experimental design (Sb × organic fertilizer × rice cultivation) to elucidate how organic fertilizers influence Sb speciation and toxicity. Organic fertilizer promoted Sb redistribution into crystalline iron-aluminum oxide-bound (+23.68 %) and residual (+51.45 %) fractions, reducing labile Sb (-51.74 %). Rice roots triggered a marked rhizosphere effect: Nsa-Sb redistribution increased by 37.82 % in planted soil but declined by 17.08 % in unplanted soil, confirming root-driven Sb activation. Fertilization reduces leaf Sb uptake (-44.22 %) and eases oxidative stress, lowering root O₂⁻, H₂O₂ and MDA contents by 33.41 %, 24.78 % and 27.01 %, while increasing glutathione (+21.63 %) and antioxidant enzyme activities (SOD+61.88 %, POD+110.51 %). Metabolomic revealed 16 Sb-responsive root metabolites reprogrammed by fertilization. Notably, organic fertilizer reversed the downregulation of the gibberellin precursor Ent-7α-Hydroxykaur-16-en-19-oate and modulated salicylic acid, arbutin and arabinitol, reflecting coordinated detoxification across amino acid, sugar and phenylpropanoid pathways. These results demonstrate that organic fertilizers orchestrate Sb immobilization, antioxidant fortification and metabolic adjustment, offering a sustainable avenue to mitigate Sb toxicity in rice systems.