Irrigation Scheme for Saline-Alkali Land Improvement: Salt Leaching and Saline Drainage & Utilization of Slightly Brackish Water

Irrigation Scheme for Saline-Alkali Land Improvement: Salt Leaching and Saline Drainage & Utilization of Slightly Brackish Water

The core of saline-alkali land improvement lies in controlling soil salinity. Key irrigation schemes revolve around two main pathways: "leaching and drainage" and "safe utilization." This involves using irrigation water to wash away excess salt and scientifically utilizing the naturally saline slightly brackish water resources.

"Salt leaching and saline drainage" is the fundamental pathway for improvement. This method is achieved through the construction of a comprehensive irrigation and drainage system. First, sufficiently deep drainage ditches are dug in the farmland or underground drainage pipes are laid to create drainage outlets. During irrigation, large-volume flooding or deep seepage irrigation is used, allowing a large amount of irrigation water (preferably low-salinity fresh water) to seep into the soil, dissolving and carrying salts from the topsoil and root zone downwards. Finally, the saline water is drained from the farmland through the drainage system. This process needs to be repeated multiple times, with close monitoring of soil salinity changes, until the soil salinity in the root zone is reduced to a level that crops can tolerate. This method of "using water to suppress salt and using water to wash away salt" is an effective means of rapidly reducing topsoil salinity.

"Brackish water utilization" is a strategy of resource recovery and adaptive management. In areas with scarce freshwater, relying solely on freshwater for salt leaching is costly. Therefore, the scientific utilization of slightly saline water with higher mineralization for irrigation becomes an important supplement. The key lies in skillful use and rotation: for example, using brackish water during the growth stages when crops have strong salt tolerance; or adopting methods such as "mixed brackish and freshwater irrigation" or "alternating brackish and freshwater irrigation," mixing or alternating the use of brackish water with limited freshwater to reduce the overall salinity of the irrigation water. Simultaneously, more comprehensive drainage measures must be implemented to ensure that after each use of brackish water for irrigation, additional freshwater or rainfall is available for leaching, preventing the continuous accumulation of salt in the root zone.

In summary, successful irrigation improvement of saline-alkali land often requires combining salt leaching and drainage projects with the resource-based management of brackish water. By constructing irrigation and drainage infrastructure to control salt movement, and then flexibly formulating irrigation strategies based on water source conditions and crop characteristics, excess salt can be drained while the limited, saline water resources can be safely utilized, gradually transforming saline-alkali land into stable productive farmland.