Biochar and zinc oxide nanoparticles partnership: a multi-faceted strategy to enhance rice productivity and remediate antimony polluted soils

Antimony (Sb) is a toxic metalloid that poses a significant threat to living organisms and ecosystem sustainability. Biochar (BC) and zinc oxide nano-particles (ZnO-NPs) are promising amendments to mitigate heavy metals toxicity. However, the potential role of BC and ZnO-NPs in alleviating the Sb toxicity remains unexamined. To address this gap, the present study investigated how BC and ZnO-NPs mitigate Sb toxicity in rice.

The study included eight different treatments: control, biochar (2%), ZnO-NPs (100 mg L^− 1), BC + ZnO-NPs, Sb stress (250 mg kg^− 1), Sb stress + BC (2%), Sb stress + ZnO-NPs, and Sb stress + BC (2%) + ZnO-NPs.

Antimony suppressed rice growth and yield by inducing oxidative stress (increased hydrogen peroxide (H₂O₂) and electrolyte leakage), enhancing soil Sb availability and its accumulation in plant tissues, while reducing hormones synthesis and soil nutrients availability. Biochar + ZnO-NPs markedly enhanced the rice yield by decreasing H₂O₂ synthesis (26.06%), EL production (25.68%), soil Sb availability (41.80%) and increasing antioxidants activities, formation of iron plaque in roots (63.60%) and soil nutrients availability. Additionally, BC + ZnO-NPs upregulated the antioxidant genes (OsAPx6, OsCAT, OsPOD, and OsSOD), and downregulated the expression of OsSMP and OsMTP1 genes associated with Sb transport, thus helping to counteract Sb toxicity.

These findings suggest that the BC + ZnO-NPs can effectively mitigate the Sb toxicity and improve rice productivity. These findings provide insights to develop the measure for remediating Sb-polluted soils, while simultaneously increasing the safe and sustainable crop production.