Freeze-thaw Saline Soil Under Underground Drainage In Hetao Irrigation Area Based On Geodetic Conductivity Meter Influence Of Hydrothermal Salt Distribution

Seasonal freezing and thawing of soil is the unique formation mechanism of soil salinization in the frozen soil regions of northern my country.The upward migration of soil water and salt during the freezing and thawing period will cause the accumulation of salt on the farmland surface,which will affect planting in the next spring.In arid and cold regions,the special law of soil water and salt migration under freezing and thawing conditions is an important factor in the occurrence and evolution of soil salinization in the Hetao irrigation area.Taking the Hetao Irrigation District in Inner Mongolia as the background,this article explores the inhibitory effect of concealed salt discharge on soil salinization during the freezing and thawing process.Five different concealed pipe treatments have been laid.From 2018 to 2020,the test area will be affected.A total of 8 samplings were carried out at 11 sampling points.Through the data analysis of the concealed pipe test area and the non-concealed pipe test area,the following results were mainly achieved:(1)During the whole freezing and thawing process,the soil moisture in the0-30 cm soil layer changes drastically.The buried depth of the concealed pipe is 1.5m and the interval is 15 m.Compared with the control without concealed pipe,the treatment of the entire freezing and thawing period is before freezing and thawing.The drainage effect of the district is obvious,and the drainage effect is the best before freezing.In 2019 and 2020,the soil moisture content of the 0-150 cm soil layer was reduced by 13.66% and 13.56% compared to the control area without concealed pipes.(2)The dominant factor of water and salt transport in the freezing process is soil temperature.During the process of the gradual decrease of soil temperature during the maximum freezing depth period,the soil temperature of the 0-20 cm soil layer is lower when the buried depth of the buried pipe is 1.5m and the spacing is 15 m.Slowly,the soil temperature of the 50-110 cm soil layer decreased rapidly again.The change trend of soil temperature in the 0-50 cm soil layer of each concealed tube is the most significant.(3)During the process of freezing and thawing,soil salinization was caused by the migration of soil salinity with water.Among them,the treatment with buried depth of 1.5m and spacing of 15 m had the best salt discharge effect compared to the control area without dark pipes,and compared with none.The concealed tube control area has the best salt discharge effect before freezing,the maximum freezing depth period,and the thawing period.In 2019 and 2020,the soil salinity of the 0-150 cm soil layer has been reduced by 34.09%,41.60%,42.48%,31.34%,and 35.11%,41.41%.The desalination effect of the concealed pipe with a buried depth of 0-70 cm under the soil layer is better than that of the deep burial,that is the concealed pipe with a buried depth of 1m is better than the buried pipe with a buried depth of 1.5m.For the concealed pipe treatment,the desalination effect of the concealed pipe in the soil layer below 70 cm is better than that of the shallow burying,that is,the concealed pipe with a buried depth of 1.5m is better than that of the buried pipe with a buried depth of 1m.