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| DOI：10.13522/j.cnki.ggps.2019265 |
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| Assessing the Efficiency of Subsurface Drain in Controlling Soil Salinization in Hetao Irrigation District |
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DOU Xu, SHI Haibin , LI Ruiping, MIAO Qingfeng, TIAN Feng, YU Dandan, ZHOU Liying
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College of Water Conservancy and Civil Engineer, Inner Mongolia Agriculture University, Hohhot 010018, China
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| Abstract: |
| 【Background】Soil salinization could cause soil desertification and land degradation, and it is a major
ecological concern affecting sustainable agricultural production almost in every country around the world. Hetao
Irrigation District is located in an arid and semi-arid region in Inner Mongolia, and it is one of the three major
irrigation areas in China. Precipitation in the region is low while evaporation is high, leading to sever soil
salinization and hampering sustainable agricultural development in the region. Open ditch drainage has been widely
used to control groundwater table and alleviate soil salinity in the district, but it often results in slope collapse in
addition to its waste of valuable land. It is also ineffective to control soil salinization due to its low efficiency in
draining water. Subsurface drain can resolve these problems while in the meantime improving soil physical and
chemical properties. 【Objective】The purpose of this paper is to assess the efficacy of subsurface drains in alleviating
soil salinization induced by irrigation in Hetao Irrigation district.【Method】We took Wulate area to the downstream
of the district as an example. Data measured from field and laboratory were analyzed using the principles of classical
statistics and geostatistics method, from which we obtained the statistical characteristics and spatial heterogeneity of
soil salt at harvest, before and after the spring irrigation, respectively. We also analyzed the effects of soil salt and its
ion composition on efficiency of the subsurface drain in desalinizing soil.【Result】The average desalination rate in
the 0~20 cm, 20~40 cm and 40~100 cm of soils was 61.14%, 52.78% and 40.37%, respectively. Subsurface drains
reduced the coefficient of variation while increased spatial autocorrelation of soil salt, indicating that irrigation after
spring reduced heterogeneity of the salt distribution. Except for CO 3 2- , the drains reduced the concentration of other
ions although HCO 3 - remained almost unchanged. The decrease in ions can be ranked in the order of
Cl - >K + +Na + >SO 4 2- >Mg 2+ >Ca 2+ >HCO 3 - . Groundwater table started dropping seven days after irrigation and soil
desalination was fast in this period. In comparison, open ditch 1.5 m deep was also effective in controlling
groundwater table.【Conclusion】Subsurface drains increased soil desalination, reduced spatial heterogeneity of soil
salt and contents of most ions. It also alleviated ion imbalance in salinization and prevented development of
salinization dominated by a few ions. Overall, subsurface drains can control groundwater table and reduce soil
salinity thereby safeguarding crop growth in Hetao Irrigation district |
| Key words: subsurface drain; soil salinity; salt ions; spatial variation; groundwater table depth |
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