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Study On Controlling Factors Of Spatial-temporal Distribution Of Soil Salinization In Typical Area Of Yongji Irrigation Area

Posted on:2021-05-01Degree:MasterType:Thesis
Country:ChinaCandidate:Z GeFull Text:PDF
GTID:2370330602962440Subject:Water conservancy project
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The count shows that soil salinization has become one of the main causes of land resource degradation,and about 100×104hm2 of irrigated arable land in the world is abandoned due to soil salinization in the annual.The Hetao Irrigation District in Inner Mongolia is the largest Irrigation District along the Yellow River in Northwest China.due to drought,low rainfall,hige vaporation,smooth terrain,and shallow groundwater,Salinization has become one of the main factors restricting the sustainable development of local agriculture,and it is a serious threat to the ecological environment of the irrigation area.Based on the field date and laboratory testing date,this paper used the classical statistics and geostatistics to analyz the spatio-temporal variability of factors affecting soil salinization and their relationship with soil salinity in the annual and middle-scale regions in the Yongji irrigation system in Hetao Irrigation District in Inner Mongolia.The research results could provide reference for the zoning of local soil salinization control measures and the precise management of land resources,and the following are the main findings and conclusions:1.The spatial variability of soil salinity in tillage in the study area was moderately strong and above,and the soil moisture,texture and groundwater level burial depth and salinity were moderately weak variability.The variation coefficient was small when the depth of groundwater level was buried and the mean degree of mineralization was large,and vice versa.The salinity and coefficient of variation of different irrigation stages(before the autumn pouring in 2018,before the first,second,third and fourth irrigation in the 2019 irrigation area,the following are referred to as the autumn before the first,the first before the water,before the second before the water,before the three waters)decreased with the increase of soil depth;the increase of irrigation times made the spatial variation of salt tend to be stable.The groundwater level varied greatly with time,but affected by spatial structural factors,the groundwater level was stable at around 2m in different periods.2.Under different types of land use in different irrigation stages,soil salinity had an accumulation phenomenon,of which wasteland was most obvious;The wasteland and grassland in different irrigation stages played a role of dry and salt drainage,and the soil salt content of the wasteland was significantly higher than that of sunflower land,corn land,wheat land and melon and vegetable land,and there was no significant difference in salt content between sunflower land,corn land,wheat land and melon and vegetable land;Except that the variation coefficient before the first irrigation was the largest in the wasteland,in other periods,last cultovated land mainly irrigated(the irrigation of corn by five waters,the irrigation of sunflower(vacant land)by one water,the irrigation of corn by two waters,the irrigation of corn by three waters,and the irrigation of corn by four waters)had a large coefficient of variation,and it indicates that irrigation will increase the spatial variation of soil salinity in the plough layer.3.Analyze the main influencing factors of solt content of cultivated soil and the relationship between the salinity of the plough layer and its main controlling factors on the spatial scale.The results are as follows:Soil texture,groundwater depth and salinity were the main controlling factors of soil salinization;Before the first irrigation and before the second irrigation,the critical depth of groundwater level before the first irrigation and before the second irrigation were 1.8m and 1.0m respectively,and the critical values of groundwater salinity were 1.5g/L and 1.3g/L respectively,and soil sand content(characterized soil texture)had a critical value of 43%and 53%(before the first irrigation and before the second irrigation,when the soil sand content at a certain point in the space was less than 43%or 53%,the risk of salinization at this point is relatively large);Compared with groundwater salinity and soil texture,groundwater depth had a greater impact on soil salinity.4.measures of prevention and control of Soil salinization:The research area should adopt integrated prevention and control measures based on water conservancy engineering measures and supplemented by agricultural and biological measures;The high-risk area of local salinization should be divided according to the main control factors,and appropriate prevention and control measures should be taken for the main control factors.
Keywords/Search Tags:Yongji irrigation sub-district, Soil salinity, Indicating the Kriging method, Principal component analysis, Dominant control factors
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