Cerium oxide nanoparticles in agroecosystems: stage-dependent impacts on sorghum growth, forage quality, bioenergy composition, and environmental risk

Engineered nanomaterials are increasingly released to agroecosystems, raising concerns about their persistence, plant uptake, and implications for crop quality and ecological risk. Cerium oxide nanoparticles (CeO₂ NPs) are widely used in industrial and consumer products and are expected to enter soils where they can interact with food, forage, and bioenergy crops. Here, growth responses, composition shifts relevant to forage and bioenergy quality, and cerium (Ce) accumulation were quantified in sweet sorghum ( Sorghum bicolor L. Moench) exposed to CeO₂ NPs in soil under greenhouse conditions. Plants were cultivated under four CeO₂ NP treatments (0, 100, 500, and 1000 mg/kg) across cut-and-regrowth stages (Cuts 1–3) and a long cultivation period without cutting (noncut). Biomass metrics were measured alongside forage and bioenergy composition traits (near-infrared spectroscopy) and tissue Ce concentrations (ICP–MS). CeO₂ NP effects were strongly stage dependent and frequently threshold-like, with relatively limited changes across lower exposure levels followed by more pronounced shifts at higher concentrations. The concentration at which traits diverged from controls decreasing from 1000 mg/kg in early regrowth to 100 mg/kg in later regrowth, indicating enhanced sensitivity with successive cut-and-regrowth. At 1000 mg/kg, compositional changes were most coordinated and commonly reflected tradeoffs between structural/carbohydrate enrichment and reduced digestibility/energy-related attributes, consistent with phytotoxic stress. Ce accumulation was higher in noncut plants than in Cut 1 and was greatest in leaves relative to stems, with the clearest dose-associated increase observed at 1000 mg/kg under long cultivation, highlighting the importance of harvest strategy and tissue type when assessing uptake and potential trophic transfer. Overall, CeO₂ NP exposure can shift sorghum quality trajectories in a management-dependent manner, indicating that harvest strategy may influence forage quality, bioenergy feedstock performance, and environmental risk in nanoparticle-impacted agroecosystems.