Study on Soil Moisture and Salt Dynamic Variation of Saline Farmland in Upper Reaches of Yellow River

The movement of soluble salts in soil is directly related to the movement of soil water,therefore,how to simultaneous and continuous determine the soil water and soluble soil salt content in cultivated soil layer,which is key for understanding the distribution of soil salinity and dynamic variation law.This paper combined soil water content and soil bulk electrical conductivity measured by Time Domain Reflectometry continuously,to calculate electrical conductivity of soil solution(ECw) and electrical conductivity of saturated soils solution(ECsat),both are closely related to soil soluble salt concentration,then analysis the dynamic change feature of soil water and salt,which is a new method.The analysis results indicated that groundwater level kept low value in one year,low than 150 cm.Soil water content in 10 cm decreased with time in our observation periods(except the soil frozen-thaw time),ranging from 20% to 45%.The variation character of soil water in 20,40,60 cm,which range from 33% to 50%,were relatively complicated.Vertically,soil water content was high in upper layer than in lower layer.Contrary to soil water,soil salt content appeared decreasing trend from the soil surface layer to deeper layer.In the most time of crop grown season,the ECw and ECsat in 10 cm fluctuated respectively in range of 10～15 dS/m and 5～10 dS/m,high then the classification criteria 4 dS/m between saline soil and non-saline soil.Compared with the soil salt change rule in 10 cm,it was still complex in 20,40 cm,which characterized by alternating high and low values.