Characteristics and influencing factors of Se content in the farmland system in Bailang County, Tibet, China

The development of Se-rich land has been carried out in many regions of China, achieving remarkable results. However, no Se-rich land or crop has been reported in Tibet. This study analyzed the characteristics and influencing factors of the Se content in the soils and crops of the key arable land areas in Bailang County, Tibet, aiming to lend support to the development and utilization of Se-rich land in the Qinghai-Tibet Plateau. The results are as follows: The soils in the study area have a Se content of (0.05~0.76)×10^-6, which is higher than the background value of soils in Tibet (0.15 ×10^-6); 76.83% of the land in the study area has sufficient Se, and land in the study area with a Se content of greater than 0.3 ×10^-6 covers an area of 45.43 km², as determined according to the standard threshold of Se content in alkaline soils (w(Se)≥0.3 ×10^-6). Further investigation shows that highland barley seeds have a Se content of (0.017~0.17)×10^-6 (average: 0.063 ×10^-6) and rapeseeds have a Se content of (0.043~0.14)×10^-6 (average: 0.078 ×10^-6) in the distribution area of Se-rich soils. As indicated by the root soil results of the zones with Se-rich soils, the Nieru Group controls the source of Se in soils, and Se and effective Se content in the soils are significantly positively correlated with N, P, alkali-hydrolyzable nitrogen, and rapid available phosphorus but is significantly negatively correlated with pH. These results indicate that the behavior of Se is significantly affected by a large number of nutrient elements in the soils and pH. Overall, the distribution areas of Se-rich soils in Bailang County have high soil environmental quality, crops with a high Se content, and great potential for the development of Se-rich plateau characteristic agricultural products.