| Selenium(Se),located in the VIA group in the fourth cycle of the periodic table of elements,has an atomic weight of 78.96.It is an essential trace element for organisms and has biological functions such as removing peroxide and preventing cell damage.Selenium is closely related to human health.Excessive or insufficient intake of selenium will have a great impact on health.Selenium is rarely transferred and enriched in the food chain,and plant selenium is the main source of selenium intake in human body.The utilization of selenium by plants is not only related to the total selenium in the soil,but also closely related to its available state.Therefore,the study on the bioavailability of selenium in soil is of great practical significance for the development of selenium-enriched industry.Taking the northwestern part of Fenggang County,Zunyi City,Guizhou Province as the research area,this paper analyzed the content and form of selenium in soil-crop system through field investigation and indoor soil pot simulation experiment,discussed the effects of soil physical and chemical properties on the bioavailability of selenium,evaluated the content and bioavailability of selenium in soil,and further explored the effects of biochar on the bioavailability of selenium in soil.The purpose of this study is to provide scientific data and theoretical basis for the development of agricultural products in selenium-rich areas of Guizhou.The main understandings and conclusions obtained are as follows:(1)The soil selenium content in Fenggang County was at the level of selenium-sufficient and selenium-enriched,and the bioavailable selenium was affected by the total amount and soil p H.The results showed that the concentration of selenium in soil ranged from 0.52 to 2.91 mg/kg,with an average of 1.56 mg/kg.The available selenium content in soil ranged from 0.00764 to 0.0308 mg/kg,with an average of 0.0163 mg/kg.The activation rate of selenium decreased with the increase of total selenium in soil,and there was a significant negative correlation between them(r =-0.49,p < 0.01),(n=106).There was a significant positive correlation between soil p H and selenium activation rate,with correlation coefficient r=0.413(n=106,p < 0.01).(2)The average selenium content of rice parts was in the order of root > grain >stem.The selenium content of grain was in the range of 0.042～0.176 mg/kg,which reached the standard of selenium-rich rice(national standard limit of 0.04～0.3 mg/kg).Selenium content in rice grain was positively correlated with total selenium content in soil of rice root(p < 0.01),and selenium content in rice root was negatively correlated with soil p H(p < 0.01).The enrichment coefficients of rice root and grain were negatively correlated with soil total selenium(p < 0.01).(3)As for tea leaves,the selenium content in new leaves ranged from 0.0055 to0.1835 mg/kg,with an average of 0.0687 mg/kg,while that in old leaves ranged from0.0265 to 0.3320 mg/kg,with an average of 0.1118 mg/kg.The selenium content in old leaves was generally higher than that in new leaves.According to the selenium enrichment standard of selenium-zinc tea in Guizhou Province(0.25-4.0 mg/kg),only one old leaf sample met the standard.The selenium content of new leaves and old leaves was positively correlated with the total selenium content of rhizosphere soil(p< 0.01),and the selenium content of new leaves was positively correlated with the soil available selenium content(p < 0.01).The enrichment coefficient of new leaves was positively correlated with the total selenium and available selenium content of rhizosphere soil(p < 0.01).There was also a significant negative correlation between the enrichment coefficient of old leaves and the available potassium in rhizosphere soil(p < 0.01).(4)Laboratory simulation experiments showed that the effects of different biochar additions on soil bioavailable selenium presented great differences.Among the three biochar treatments,the content of available selenium in pig manure biochar treatment group increased the most.When the experiment was completed,the content of available selenium in soil in 1.0% group,3.0% group and 5.0% group were:Compared with blank control group,the increases of 22.96μg/ kg,27.69μg/kg and23.87μg/kg were 3.65%,25.01 % and 7.76%,respectively.In the apricot shell biochar treatment group,the effective selenium content in 1.0% group,3.0% group and 5.0%group was 21.89 μg/kg,23.6μg/kg and 20.95μg/kg,respectively.Only the effective selenium content in 3.0% group was higher than that in the blank control group.In the rice straw biochar treatment group,the available selenium contents in 1.0% group,3.0% group and 5.0% group were: At 21.85 μg/kg,20.01μg/kg and 19.61μg/kg,the available selenium content in soil decreased by 1.35 %(1.0%),9.66%(3.0%)and11.47 %(5.0%),respectively.After the three biochar treatments,soil p H and organic matter contents increased,and the values increased with the increase of biochar application amount.The selenium content in tea was proportional to the amount of biochar added in pig manure.The selenium content in tea reached 89.56μg/kg when the biochar dosage was 5.0%,which was significantly higher than that in the control group(68.16μg/kg). |
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