Analysis Of Nutrient Elements Distribution And Its Influencing Factors In Enshi Selenium-rich Area

Enshi is one of the typical soil distribution areas with high selenium content.This paper analyzed the distribution characteristics and influencing factors of nutrient elements and their effective states in the soil of Shadi village,Enshi City,Hubei Province.It also evaluated the geochemical status of cultivated land and the zoning of safe land utilization.The research results were of great significance for the selenium rich areas to adjust measures to local conditions.At the same time,it was also helpful in increasing the output of crops and promoting the development of agriculture.The main conclusions were as follows:1.The variation coefficients of molybdenum(Mo)and selenium(Se)in the surface soil of the study area are 1.80 and 1.65,respectively.It was indicating that the two elements are highly dispersed and the content of different stratigraphic types vary greatly.Except potassium(K),the average content of other soil nutrient elements in the study area was higher than that in Hubei Province and the whole country.2.The geochemical grades of the nutrient elements except K in the study area were mainly first-and second-class.The total area of the first-and second-class plots of selenium accounts for 86.96% of the total study area.3.There was no significant correlation between soil pH value and most nutrients or available states in the study area.Soil organic matter(SOM)had a significant positive correlation with most of the soil nutrients(including N,P,Cu,Mo,Zn,Se)at the level of 0.01,and also had a significant positive correlation some soil nutrients available states(including nitrate N,effective P,Effective B,water-soluble Se)at the level of 0.01.In terms of different soil textures,the average content of N,B,Mn,Zn and their available states,and P,K,Cu were relatively high in clay.Mo,Se,and water-soluble Se were high in silty loam.The average content of soil available K and soil available Cu showed a downward trend as the soil texture became finer.Due to the existence of black rock series,the content of Mo and Se elements and water-soluble Se in the soil of the study area were the highest in the Maokou Formation of Permian.4.There were differences in nutrient content of different soil types in the study area.N,P,nitrate N,available P and water-soluble Se were higher in brown soil than other soil types.And the average content of Mo and Se was higher in yellow brown soil than other soil types.The N,P,Cu,Mo,Mn and Se in the soil of the study area were significantly correlated with their corresponding nutrient availability at the level of 0.01.In addition to the close relationship between Se and Mo,there was a high correlation between Se and heavy metal elements such as Cd.5.Based on the maize cadmium absorption model and human health dose effect,the environmental concentration of soil cadmium in the selenium-rich area was calculated to be 0.98 mg/kg,and the safety zoning of typical selenium rich areas in Enshi was carried out.The results showed that the proportion of priority protection,safety utilization,structural adjustment and strict control of cultivated land area in the study area was 58.85%,22.90%,0% and 18.25%,respectively.