Aims <p>Safe utilization of limited selenium (Se)-rich soil resources has gained increasing attention for improving Se nutrition while minimizing the accumulation of coexisting cadmium (Cd) in rice. However, the roles and mechanisms through which rice variety, growth stage, and soil amendments regulate Se and Cd dynamics in the soil-rice system remain insufficiently understood.</p> Methods <p>This field study evaluates the effects of hydrated lime and rice-husk biochar on grain Se and Cd concentrations in two rice varieties with contrasting Se and Cd accumulation characteristics.</p> Results <p>Soil Se bioavailability and plant Se concentration declined, whereas those of Cd rapidly increased from tillering to maturity. The low-Cd-accumulating rice variety Xiushui 519 showed lower shoot to grain Se/Cd translocation than Yongyou 8, resulting in 27% lower Se and 77% lower Cd concentrations in grains. During the vegetative period, application of hydrated lime and biochar increased available Se in the rhizosphere and Se concentrations in root and shoot by 49%, 42%, and 28%, respectively, while reducing Cd in the rhizosphere, root, and shoot by 55%, 37%, and 52%. Cultivation of Xiushui 519 with hydrated lime further reduced grain Cd by 84%. In Yongyou 8, application of hydrated lime and biochar decreased grain Cd by 43% and 24%, and increased grain Se by 41% and 14%, respectively.</p> Conclusions <p>These results provide valuable insights into strategies for safely producing Se-rich rice through optimized varietal selection and soil amendment practices.</p>