[Objective] The distribution status and availability of soil selenium in three jujube orchards in Minqin County

Gansu Province was analyzed in order to provide a theoretical basis for the development of the selenium-enriched jujube industry.[Methods] The contents of total selenium and various forms of selenium in the 0-60 cm soil layer in three jujube orchards of Minqin County were measured by a method of successive extraction. Jujube distribution characteristics and availability were determined.[Results] ① The total selenium content was 24-520 μg/kg (average was 210.625 μg/kg)

suggesting that total soil selenium was not deficient. ② Total soil selenium content increasingly declined with increasing soil depth in the 0-60 cm soil layer

with values in the three orchards following the order of Liugou>Zhangba>Xinguoyuan. According to the partition criterion for soil selenium content

the surface soil (0-20 cm) was categorized as selenium-rich; the subsurface soil (20-40 cm) was selenium-rich and selenium-poor; and the bottom soil layer (40-60 cm) was selenium-rich

selenium-poor

and selenium-deficient. ③ The available selenium content was 42.5 μg/kg and accounted for 20.2% of total selenium. Soluble selenium was 1.1-1.4 μg/kg

exchangeable selenium was 1.4-2.8 μg/kg. Both of these selenium forms together accounted for only 7.7% of the available selenium. The remaining available selenium was all organic selenium. ④ The available soil selenium increased with increasing number of reclamation years and followed the order of Xinguoyuan>Liugou>Zhangba among the three orchards. ⑤ The contents of total selenium

available selenium

and ineffective selenium were greater under trees than between tree rows.[Conclusion] Total selenium was not deficient in the soil of jujube orchards of Minqin County

but available selenium was deficient. Hence

development of the selenium-enriched jujube industry will require artificially supplementing soils with selenium fertilizer.