Analysis And Evaluation Of Spatial And Temporal Variation Of Soil Salinization In Typical Area Of Yongji Irrigation Area

The prevention and control of soil salinization is not only of great significance to the sustainable development of agriculture and ecological environment,but also the need to ensure national food security.In this paper,a medium-scale area in Yongji irrigation area of Hetao irrigation area was sampled(10 times in total from the fifth water in 2018 to the third water in 2020),and the spatial-temporal distribution of soil salinization in the annual period of Hetao irrigation area was analyzed.Through the construction of comprehensive indicators,the spatial-temporal distribution of soil salinization and its relationship with various influencing factors were analyzed and evaluated,which can provide reference for the control of soil salinization,the adjustment of planting structure and the formulation of irrigation and drainage system..The following are the main findings and conclusions:1.The salt content of 0-10cm soil layer in each period is about twice of that of 10-20cm and 20-40cm soil layers.The salt content of soil is surface accumulation type,and it is in the state of salt accumulation in summer irrigation period.The effect of salt drainage in salt wasteland is significant.2.The spatial structure of soil salt in the study area had little change from the first irrigation to the fifth irrigation.The distribution pattern of salinization in different periods of the same year was similar,but the degree of salt accumulation and salinization area increase gradually with time,which showed it is more important to desalinize by irrigating in autumn under the condition of water-saving irrigation.3.Based on the information of soil texture,groundwater depth and groundwater salinity,ground elevation,the shortest distance from ditch(SDTD),the shortest distance from wasteland(SDTW),etc.,The comprehensive evaluation index of soil salinization was constructed,The coefficient of determination between the comprehensive index and the measured value of soil salinity in each period is R2=0.46?0.69,and the similarity between the comprehensive index and the corresponding spatial distribution map of salinity in each period is between 62%and 81%,which indicates that the comprehensive index can well explain the spatial variation of soil salinity in the plough layer,It can be used as a risk assessment index of soil salinization,that is,the greater the comprehensive index value of a certain point,the greater the risk of soil salinization;at the same time,without salt information,the index can be used to estimate the spatial distribution pattern of soil salinity.4.The groundwater depth and SDTW are the main factors of the temporal and spatial variation of soil salt in the cultivated layer of the study area.The sand content and SDTD are the second,and the influence of ground elevation and groundwater is relatively small;the critical value of comprehensive index for the light salinization of the soil in the seedling stage of crops is determined to be about 2.4.5.1n view of the typical area I where the main controlling factors of soil salinity are groundwater depth and SDTD,the buried underground pipes are selected as the main drainage and salt control measures in this area,and the buried depth of the underground pipes is 2.1m,and the spacing is 48m;in view of the typical area ? where the main controlling factor of soil salinity is SDTW,When the ratio of cultivated land to wasteland is about 3:1,the effect of drainage and salt control can be achieved.