Abstract: 【Objective】This study was conducted to investigate the effects of sulfur (S) on the fractions and species of amended selenite in soil by applying S fertilizer, and explore the mechanism through which S controls the selenium (se) uptake of wheat. 【Method】Wheat (Triticum aestivum L. cv. Zhengmai 9023) was chosen as the test material, and underwent seedling stage soil cultivation and solution cultivation. A potted soil experiment was performed on wheat and the application amounts of S were 0, 150, and 300 mg?kg^-1, respectively, Sulfur was used as S source, Se source was selenite (Na₂SeO₃) and it was designated at 0 and 5 mg?kg^-1. The wheat seedlings were harvested on the 70^th day after sowing and soil samples were taken. The treatments started two weeks after the seedlings were planted in hydroponic experiment which the nutrient solution was made with 1/5 Hogland-Arnon formula. Different amounts of S were added in the experiment: 0, 0.1, and 2 mmol?L^-1; Se was designed at 10 µmol?L^-1. Se and S was supplied to plants in the form of sodium selenite (Na₂SeO₃), sodium selenate (Na₂SeO₄?10H₂O) and magnesium sulfate (MgSO₄?7H₂O), respectively. Wheat was harvested after 24 h. A fully interactional design was performed and each treatment was repeated four times in potted soil experiment and hydroponic experiment. The hydride generation atomic fluorescence spectrometer model HG-AFS-8220 was used to measure the Se content in shoot and root of wheat and soil. Based on the Se absorption of plant and the correlation of selenium content in soil, Se content in the soil was divided into different fractions and species. 【Result】Applications of both Se and S resulted in stimulation to wheat growth with appropriate amount. S was applied at 150 mg?kg^-1 significantly reduced the content and accumulation of Se in shoots and roots of wheat by 61.7% and 35.5% , 55.7% and 24.7%, respectively, but such reduction won’t change significantly with the increasing S application to soil. Application of S significantly decreased the pH value and obviously increased the organic matter content as much as 0.5 units and 0.78 g?kg^-1, respectively. Application of S significantly decreased soluble Se and increased Fe/Mn oxide-bound Se, also increased organic matter-bound Se and residual Se obviously, with no significant effect on exchangeable Se, showing that S application can prompted the passivation of Se in soil. Application of S also significantly decreased the content of various Se species in the soluble Se, and obviously increased the content of Se(IV) and significantly decreased the content of Se(VI) in the exchangeable Se, showing that application of S retarded the conversion of Se to the efficient species in soil. S had a profound effect on the intake of Se by wheat seedlings when Se(IV) and Se(VI) was applied. The Se content in shoot and root of wheat in the Se(VI)-treatment was 44.7 and 22.4 times, respectively, the content in Se(IV)-treatment, while with a S rate of 1 mmol?L^-1, their Se contents were less than 2.8 times and 51.8% of the Se(IV)-treatment, showing that S application significantly reduced the differences of absorption capacity in wheat between the treatments of Se(IV) and Se(VI). 【Conclusion】In addition to improving wheat growth, an appropriate amount of S fertilizer can reduce soil pH and increase organic content, causing soluble Se in soil to be Fe/Mn oxide-bound, organic matter-bound and residual Se, and retarding the conversion of Se(IV) to Se(VI) in the exchangeable Se, thus reducing Se uptake by wheat. Therefore, the content of Se in crops can be effectively controlled by increasing S in the high Se and deficient S area and reducing S in the deficient Se and high S area.

Key words: common wheat, selenite, sulfur, selenium fraction, selenium species