Under the combined application of selenium and sulfur, sulfur does not interfere with selenite uptake in Tartary buckwheat.

Selenium and sulfur present comparable physicochemical properties and have similar absorption and assimilation pathways in crops. The factors influencing absorption in crops are often attributed to the interaction between sulfur and selenium. Therefore, investigating the effect of sulfur on selenium absorption in Tartary buckwheat is crucial. In a two-year pot experiment, Tartary buckwheat "Heifeng No. 1" was used, and a random block design was adopted. Four selenium levels (0, 0.25, 0.5 and 1 mg/kg) and five sulfur levels (0, 40, 80, 100 and 200 mg/kg) were set for soil-based application to study the effects of combined selenium and sulfur application on the selenium content in various tissues of Tartary buckwheat plants. For the treatment, S0Se0 was used as the CK treatment. Research has demonstrated that the application of selenium significantly increased the selenium content in various tissues of Tartary buckwheat plants at different growth stages, which was positively correlated with the concentration of selenium that was applied. The selenium content in different tissues of Tartary buckwheat plants is distributed mainly in the roots and leaves at the seedling stage, in the grains at the maturity stage and in the leaves at other stages. The combined application of selenium and sulfur influenced the selenium content in each tissue of Tartary buckwheat plants; however, under identical selenium concentrations, varying sulfur concentrations did not significantly affect selenium levels in different tissues. These findings provide a basis for the production of safe selenium-enriched Tartary buckwheat products in extensive sulfur-deficient regions.