Review of drainage engineering practice for saline-alkali soils in Ningxia

【Background and Objective】Soil salinity is a common challenge for crop production in Northwestern China, and various engineering and agronomic methods have been developed to alleviate or reclaim saline-alkali soils. This paper reviews the advantages and disadvantages of drainage engineering methods, including open ditches, buried drains, and boreholes, for treating saline-alkali soils in Ningxia Province. It proposes the most effective drainage methods for saline-alkali soils in different regions, aiming to provide protocols for improving soil management in the province.【Method】This review focuses on work conducted in regions such as Huinong District and Pingluo County in Shizuishan City, Helan County and Xingqing District in Yinchuan City, and Hongsipu District in Wuzhong City. Literature and engineering data were collected from various sources to analyze and identify the appropriate drainage methods for each region. The VOSviewer was used to analyze and summarize key research topics related to drainage engineering methods for reclaiming saline-alkali soils in the province. 【Result】①The primary drainage systems for saline-alkali soils in the province include open ditches, supplemented by buried drains and pumping boreholes. Maintenance of these systems should be strengthened to improve their effectiveness and operational efficiency. ② In Huinong District and Pingluo County, located in low-lying areas near lakes and wetlands, the soil has low permeability, and buried drains and pumping boreholes are the most appropriate methods to maintain the groundwater table below a critical depth. In areas with clayey soils, combining these methods with soil barrier removal would enhance efficiency. ③ In Helan County and Xingqing District (Yinchuan City), the cultivated saline-alkali soils require drainage ditch maintenance and protection. A combination of boreholes and buried drains should be considered based on local conditions. ④ In Hongsipu District (Wuzhong City), topsoil salinity can be reduced by leaching using ditch drainage, while salinity in the subsoil can be managed with buried drains or leaching using borehole pumping. 【Conclusion】 Drainage engineering practices are critical for reclaiming saline-alkali lands in Ningxia Province. Selecting an appropriate drainage method based on regional characteristics is essential to improving reclamation efficiency. Future research should focus on combining engineering, biological, chemical, and physical methods to better manage saline-alkali soils in the province.