Evaluation of the rainfall effectiveness for reclaim of saline soil by subsurface pipe drainage system in coastal saline regions of Hebei Province

Shortage of fresh water and bad irrigation facilities limited reclamation of saline soil by using subsurface pipe drainage system in coastal regions of Hebei Province with saline-alkali wastelands and low-yield farmlands. This made the utilization of rainfall a significant production practice in the region. Using Huanghua City as a case, this paper analyzed the rainfall features and effects of rainfall on the subsurface pipe drainage for saline soil reclamation in the coastal saline regions of Hebei Province. The study showed that at soil salt content below 0.3%, precipitation induced soil leaching and absolute desalinization. At soil salt content above 0.3% and below 0.5%, precipitation only induced soil leaching and desalinization when pipes were buried at proper depths and soils readily leachable. At soil salt contents above 0.5%, soil leaching and desalinization never occurred under whatever precipitation level. Under the current pipe conditions, precipitation in rain season of June through September induced significant leaching of slight saline-alkali soils. In severe saline-alkali soil regions, precipitation in the rainy season was not sufficient to leach and desalinize the soils. Based on rainfall analysis, there was a decreasing trend in annual precipitation. The frequency of drought also increased against that of flood. Application of long-term subsurface pipe drainage for saline soil reclamation should consider deficit irrigation to supplement rainfall and induce leaching in saline-alkali soils.