| Selenium is an essential micronutrient in the human body and has multiple important physiological functions.The selenium required by the human body is mainly ingested through the food chain,and the selenium in the food chain mainly comes from soil.Therefore,the efficient utilization of selenium rich soil has received increasing attention.Enshi is a typical selenium rich region in Hubei Province,where the soil selenium content is rich but there is a problem of low soil selenium availability.Therefore,improving soil selenium availability is the key to ensuring high-quality selenium rich agricultural products.The availability of soil selenium is closely related to its occurrence form,and microorganisms can participate in the process of soil selenium transformation through their own metabolism,affecting the availability of soil selenium.Based on this,this study selected four commonly used Bacillus strains in microbial fertilizers as experimental strains to explore the effectiveness and mechanism of Bacillus in improving soil selenium availability.The differences in soil selenium conversion efficiency among different Bacillus strains were explored through the absorption and utilization characteristics of soil selenium by pakchoi;Exploring the mechanism of Bacillus promoting soil selenium transformation through the transformation characteristics of soil nutrients and soil selenium forms,as well as the adsorption and desorption of selenium by soil,aims to provide theoretical support for the efficient utilization of selenium rich soil.The main results of this study are as follows:(1)Bacillus species can effectively promote the growth of pakchoi and increase its selenium accumulation,with Bacillus species having the best effect on enhancing selenium accumulation.The results of the pot experiment showed that the selenium content in the aboveground parts of pakchoi without inoculation with Bacillus species could reach 1.74 mg/kg,and the accumulated selenium in the aboveground parts was 2.74μg/plant,after inoculation with four types of Bacillus,the selenium content increased to 1.89-2.28 mg/kg,and the aboveground selenium accumulation increased by 1.52-2.78μg/plant,in which the accumulation of selenium in the aboveground part can reach 5.52μg/plant under the treatment of Bacillus megaterium.(2)Bacillus megaterium can enhance the selenium absorption capacity of pakchoi,and increase the selenium transport coefficient of pakchoi,thereby increasing the accumulation of selenium in the aboveground parts.Moreover,the selenium rich Bacillus megaterium absorbed by selenium can be absorbed and utilized by pakchoi.The solution culture experiment showed that at a selenium concentration of 0.5 mg/kg,the selenium transport coefficient of non inoculated pakchoi was 0.059,which increased to 0.074 after inoculation,and the aboveground selenium accumulation increased from 1.46μg/plant increased to 1.99μg/plant.When selenofemacillus was used as the only selenium source,selenium rich Bacillus with selenium content of 40μg and600μg increased the accumulation of shoot selenium by 0.08μg/plant and0.23μg/plant,respectively.(3)Bacillus species can promote the transformation of insoluble selenium into exchangeable selenium in soil,thereby improving the availability of soil selenium and increasing the content of available phosphorus in the soil.The results of soil culture experiments showed that after inoculation with 2 m L1×10~8/m L suspension of Bacillus species in Enshi selenium rich soil,the effective selenium content in the soil significantly increased with the prolongation of cultivation time.After 14 days of cultivation,the effective selenium content in sterilized soil increased from 0.64 mg/kg to 0.72 mg/kg,with the exchangeable selenium content increasing from 0.44 mg/kg to 0.49mg/kg,and the proportion of total selenium increased from 4.96%to 5.74%.At the same time,the effective phosphorus content in the soil has also increased from 14.40 mg/kg to 16.64 mg/kg.(4)The increase in available phosphorus content in soil can promote the desorption of soil selenium and improve the effectiveness of soil selenium.The results of soil simulation experiments show that adding phosphorus to the selenium rich soil in Enshi can significantly increase the desorption of soil selenium.When adding 10-300 mg/L phosphorus,the total desorption of soil selenium increases from 0.13 mg/kg to 0.86 mg/kg,mainly increasing the desorption of selenite from 0.03 mg/kg to 0.78 mg/kg. |
