Study On Selenium Bio-availability Of Soil In Potentially Selenium Enriched Soils In Lujiang County,Anhui Province

It is a necessary nutrient element of Se for humans and animals.Soils Se deficiency leads to low Se content in food plants and insufficient intake of Se in foods in most parts of China.Rice is one of the staple foods in China.Increasing the Se content of rice can improve the dietary nutrition of Se safely and effectively in China.The multi-objective study of the Yangtze-Huaihe river basin in Anhui Province found that the soil total Se content was greater than 0.5 mg/kg in the Fanshan and Longqiao areas of Lujiang County in Anhui Province.The basic characteristics of the Se-enriched soil and the development potential of Se-enriched rice were preliminary.Therefore,the study on the bio-availability of soil Se in potential Se-enriched areas is of great significance to the scientific delineation of Se-enriched soils and the further development of Se-enriched rice.A total of 68 paired samples of rice and the corresponding root soils were collected from Lujiang County,Anhui Province which is potential Se-enriched areas,to analyze soil physicochemical properties,nutrient abundances,Se concentrations,different forms of Se and Se content of rice,and to study the migration and transformation of Se in soilrice system.Relevant analysis,linear regression,and path analysis were used to explore the influencing factors of soil Se bioavailability and the criteria for the classification of Se-enriched soils were explored based on bioavailability.The conclusions were as follows:(1)The soils of rice roots in the survey area are acidic,with moderate fertilizer retention capacity,and rich levels of total nitrogen,alkali-hydrolyzable nitrogen,available iron,available manganese,and total sulfur.The contents of total phosphorus,available phosphorus,and available potassium are moderate.The soil in the study area contain 0.260-1.177 mg/kg Se and 56.2% of soil samples satisfies Se-enriched soil standards(>0.40 mg/kg).And the rice in the study area contain 0.037-0.242 mg/kg Se and 98.5% of rice satisfies the criteria of Se-enriched rice(>0.04 mg/kg).The significant difference in the ratio of Se-enriched soil and Se-enriched rice indicates that the development of the Se-enriched soil standard must be based on the Se content of the soil in combination with the soil Se bioavailability and other soil factors.(2)Soil Se of rice roots concentrations have a strong positive correlation with soil total sulfur,total phosphorus,total nitrogen.The forms of Se in the soil samples were mainly distributed between humic acid bound phases(15.5%-31.5%),strongly bound organic phases(12.5%-38.6%),and residual phases(8.1%-68.5%),with a small amount of Se exists in the water-soluble,ion-exchanged,carbonate-bound,and iron-manganese oxidation states.The morphology of soil Se is affect by Soil pH,CEC,organic matter,total nitrogen,total phosphorus,total potassium,total sulfur,total iron,etc.The highest proportion of organic Se(humic acid Se and strong organic state)is most significantly affected by organic matter content.(3)The Se content of rice was significantly affected by soil humic acid Se,strong organic Se,extractable Se,available potassium,and CEC.Soil available sulphur and available phosphorus improve Se absorption in rice seeds(rice)by increasing the strong organic phases Se,humic acid bound phases Se,and extractable Se.While the soil cation exchange capacity,available potassium,total iron,and total manganese inhibit Se absorption in rice seeds(rice)by reducing the bioavailable Se content of rice(including water-soluble,humic,strong organic,and Se).(4)The Se-rich ability of middle rice is more than late rice and glutinous rice than glutinous rice.The concentration of Se in various organs of rice(in terms of mass fraction)was in the order of root> leaf> stem> brown rice> polished rice.Rice roots have strong absorption of Se in the soil,and their transport capacity is relatively weak.(5)The derived variables "ratio of total Se to OM"(NRE-Se/OM)and "ratio of nonresidual Se to OM"(Setot/OM)represent the Se content and morphology in the organic matter of the soil.Its representative bioavailability of soil Se is strong.This study used a multiple stepwise lineal logarithmic regression approach combined with NRE-Se/OM values,effective S and Fe soil concentration data,and total Mn soil concentration data to generate a model for Se uptake by rice,with some 76.0% of the variance in the model being explained by variations in these values.Significantly improve the accuracy of rice Se content prediction.Based on scientificity considerations,when Se exists mainly in the organic state in acidic soils,the rice produced from NRE-Se/OM ? 0.080 soil can meet the requirement of Se-enriched rice;based on cost considerations,the rice produced in Soil Setot/OM ? 0.086 reaches the rich Se rice requirements.