Analysis Of Soil Physical And Chemical Properties And Soil Quality Evaluation In Dunhuang City

Soil resources is a very fragile non-renewable resources. Maintaining soil quality and soil quantity become the basis for sustainable development of agriculture. The ecological environment of Dunhuang region is extremely fragile. Soil degradation in this area, such as salinization and desertification, is serious. Therefore, study of soil properties and evaluation of soil quality play decisive roles to alleviate the ecological frangibility, improve environmental quality, restore ecological function. In order to analysis the physical and chemical properties as well as the soil quality characteristics of the soil in the Dunhuang region, this study which based on the field investigation and soil sampling, used several analytical methods like correlation analysis and fuzzy comprehensive evaluation to analysis particle size,moisture, salinity, PH, organic matter, nutrientsetc of the soil in Dunhuang region, and then evaluated the soil quanlity. Finally, this study got following conclusions:(1)Physical and chemical properties of the study area:as to soil composition,the soil particles are mainly composed of coarse silt and fine sand, and with the increase of soil depth, the proportion has a fluctuation in a small amplitude. The content of clay whichis extremely low ranges between sand and coarse sand.As to moisture content, topsoil has lowest moisture content, and with the increase of soil depth, the moisture content increase.the soil in Dunhuang region belongs to alkaline soil, and the PH ranges from 7.76 to 8.16. With the increase of soil depth, organic matter content is going to be less. Vertical distribution of soil nutrients is more uniform and stable. The content of soil total nitrogen, organic matter and alkali-hydrolysable nitrogen is found at low levels. Thetotal phosphorus and available phosphorus content is found at medium levels. And the content of total potassium and available potassium is at high levels. The content of salt is 7.7g/kg or more, and every layer of soil is in a state of salinization. The upper layer and the middle layer belong to salt accumulation layer with high content of salt. The total salt content and ion content of the soil profile has a strong variability.In the surface, the content of seven different kinds of salt ions shows some form of aggregation, and with the increase of depth, shows a law of diminishing.In Dunhuang region, the surface soil salinization is worse. About 71% of the samples of soil have the tendency of salinization, which is 2.4 times more than the non- saline soil. The main type of salinized soil in Dunhuang region is sulfate salinized soil, followed by sulfate-chloride salinized soil and chloride-sulfate salinized soil.(2)Correlation characteristics of soil properties:salt ions like Mg2+、K+、NO3- and SO42- were significantly associated with the particles, Na+、Mg2+ was significantly correlated with coarse sand, and the remaining salt ions and various size fractions are not closely correlated. Total salt was significantly positively correlated with clay, fine silt and the silt and showed significant negative correlation with the coarse silt, fine sand, coarse sand and medium sand. Fine particles have function of adsorption with total salt, and coarse particles is not conducive to accumulation of salt. Soil total salts had a significant positive correlation between soluble base cations and the organic matter, organic matter on which the Na+、Cl- adsorption is more obvious, and the adsorption of NO3- weak. Total potassium content available K+ content and fine clay, coarse clay, fine silt, the silt, coarse silt these smaller particle size was a significant positive correlation between the total nitrogen content only with coarse sand the content was negatively correlated with the content of other grain level correlation is weak. The total phosphorus, ammonium nitrogen, available phosphorus, nitrate content relationships with various size are not content closely. All organic matter and nutrients in addition to potassium showed significant correlation.(3)Contrast of physical and chemical characteristics under different circumstances: During the main sampling areas:wetland soil moisture Nansen maximum, minimum Yumen Pass region, Dunhuang oasis in the hinterland and the sun off the water content of the middle region, little change in water content with depth, the sun off the water content is less than the Dunhuang oasis in the hinterland areas. Yumen Pass the salt highest, followed by Nansen area and nearby oasis area, salt lowest Yang Guan sampling area. Soil Salinity different vegetation communities in the study area, the growth of black fruit wolfberry soil salinity highest overall, especially in the upper surface and soil salinity is higher reeds, tamarisk and tamarisk+ sparsifolia Associated smaller volume of soil salinity. Soil nutrients, and soil organic matter content associated tamarisk sparsifolia up, black fruit wolfberry and tamarisk also higher, Haloxylon dead organic matter and nitrogen content to a minimum, all types of higher total K and available K content and volatility larger. Different land use types soluble salt ions Na+, K+, Cl-, SO42- and total salt produced a significant impact. In addition to salt ions Mg2+, NO3- small remaining salt ions affected overall by the soil depth, Na+, Cl-, SO42- and the variation of the total salt is similar, are sorted in descending wasteland> shrub land> farmland> orchard, while K+ and other salt ions different content than wasteland shrub land, farmland and orchards. The impact of land use on nutrient medium, TN orchards and farmland, total phosphorus, total potassium, organic matter content than the low shrub land, and physical clay content of the highest in the farmland, wasteland of organic matter and physical clay minimum content, farmland and orchards in available K and available nutrients nitrogen content is also lower than the shrub land. Wasteland full of potassium and potassium were higher effective description of the content of potassium in soil and soil parent material related.(4)Evaluation of soil quality in the study area:Integrated soil quality sorting Dunhuang four different sampling areas for NanQuan> Dunhuang Oasis> Yang Guan>Yumen Pass, higher soil quality NanQuan area, Dunhuang oasis and soil quality sun off sampling area belong to a higher level, though, but due to the interference of human activities NanQuan area leading to inferior quality; soil quality Yumen Pass sampling area belong to the middle level. Soil quality score results for different vegetation communities:tamarisk+sparsifoliaAssociated>tamarisk> sparsifolia> black fruit wolfberry>Haloxylon> reed> Haloxylon dead, scores between 0.54 to 0.86,soil quality basic medium level. Different land use types on soil quality affect results:shrub land> orchard> farmland> wasteland, organic matter content of soil quality resulting in less farmland and orchards are below shrub land, but also shows the quality of farming activities will reduce the fertility of the soil, thus reduce soil quality. Wasteland due to lack of biomass lead to nutrient deprivation, high salt content, coarse particle size leads to nutrient soil moisture loss, it is the worst soil quality. Woodland shrubs and orchard soils are not degraded soil, and farmland has been a slight deterioration due to fanning.The degree of degradation of the wasteland was worst.