Abstract: This study aims to optimize the combined application scheme of activated iron tailings and selenium-rich mineral powder, providing both technical and theoretical support for promoting selenium accumulation and growth of rice. A pot experiment was conducted. The application level of activated iron tailings was set at 600 kg·hm^-2. There were four addition levels of selenium-enriched mineral powders (CK: 0 kg·hm^-2; Se10: 75 kg·hm^-2; Se20: 150 kg·hm^-2; Se30: 225 kg·hm^-2), along with a sodium selenate treatment (SS20: 1000 kg·hm^-2 silicon fertilizer + 0.48 kg·hm^-2 sodium selenate). We analyzed the effects of the combined application of activated iron tailings and seleniumrich mineral powder on selenium accumulation and physiological and biochemical indices of rice, clarified the optimal application level of selenium-rich mineral powder, and revealed the synergistic mechanism of activated iron tailings and selenium-rich mineral powder to promote rice growth. Results showed that the Se20 treatment was the optimal one, with a rice selenium content of 0.43 mg·kg^-1, representing a 437.50% increase than CK. The highest dry matter per plant was 12.10 g. Furthermore, at the tillering stage of rice, the superoxide dismutase activity and catalase activity of leaves in Se20 group were 49.29% and 63.24% higher than those in CK, respectively. The co-application of activated iron tailings and seleniumrich mineral powder enhanced rice oxidative stress resistance, reduced soil pH and electrical conductivity, and increased soil available silicon and organic carbon content, and thereby increased dry matter accumulation and rice growth.

Key words: rice, activated iron tailings, selenium-rich mineral powder, selenium content