Currently, soil salinization has become a problem. Saline alkali land refers to the phenomenon where the groundwater level increases, mineralization increases, coupled with climate drought and strong evaporation, leading to the migration of deep soil salt to the surface soil, and the degree of surface soil salinization or alkalization increases.
Soil salinization can be divided into two categories: primary salinization and secondary salinization. The natural occurrence of soil salinization, which is not affected by human activities, is called primary salinization; The soil salinization caused by human activities is secondary salinization.
（1） Natural conditions
Salt moves with water, and both soil and groundwater contain a certain amount of salt. Therefore, the movement of soil water has an important impact on the accumulation of salt in the soil. The shallower the groundwater, the stronger the evaporation effect, and the more likely it is to cause surface salt accumulation. It can be seen that the depth of groundwater affects soil salinization to a certain extent.
1) Climatic conditions
In the arid and semi-arid regions of Northeast, Northwest, and North China, precipitation is low, evaporation is high, and salt dissolved in water is prone to accumulate on the surface of the soil. Climate conditions have an important impact on the movement of water. Atmospheric precipitation can supplement surface water and groundwater, and atmospheric water evaporation causes upward movement of soil water. It can be seen that climate conditions are an important prerequisite for triggering soil salinization. In the arid and semi-arid areas of northern China, soil evaporation is greater than rainfall, and soil salt moves upwards with the evaporation of water, causing salt to accumulate on the surface of the soil. This process, which is repeated for a long time, can cause soil salinization.
2) Geographical conditions
The height of the terrain has a significant impact on the formation of saline alkali soil. The height of the terrain directly affects the movement of surface water and groundwater, which is closely related to the movement and accumulation of salt. From the perspective of the large terrain, water-soluble salt moves from high to low with water and accumulates in low-lying areas. Saline alkali soil is mainly distributed in inland basins, mountain depressions, and flat plain areas with poor drainage, such as the Songliao Plain. From the perspective of small terrain (within a local range), the situation of soil salt accumulation is opposite to that of large terrain, where salt often accumulates in small convex areas.
3) Geological conditions
The thickness of the texture can affect the speed and height of soil capillary water movement. Generally speaking, the capillary water in loamy soil rises faster and has a higher height, while the salt accumulation in sandy soil and clay is slower. The key issue of groundwater affecting soil salinity and alkalinity is the level of groundwater level and the degree of mineralization of groundwater. High groundwater level, high mineralization, and easy salt accumulation.
4) Hydrological conditions
The land on both sides of the river and the channel, due to the lateral seepage of the river, raises the groundwater level and promotes salt accumulation. Coastal areas can form coastal saline alkali soil due to seawater immersion.
（2） Human activities
Human activities mainly affect the degree of soil salinization by changing natural conditions. If some places flood with water during watering, or low-lying areas only irrigate without drainage, causing the groundwater level to quickly rise and accumulate salt, turning the original good land into saline alkali land, this process is called secondary salinization. To prevent secondary salinization, water conservancy facilities should be equipped with drainage and irrigation facilities, and flood irrigation is strictly prohibited. After irrigation, timely plowing and hoeing should be carried out.
