Study on shallow mild saline groundwater use safety in winter wheat irrigation based on the subsurface drainage system in the coastal area of Hebei Province in China

There is a shortage of irrigation water resources in the coastal saline-alkali land of Hebei Province, which is rich in shallow saline water resources. Appropriate saline irrigation during the critical period of winter wheat growth could alleviate the irrigation crisis in this area. In this study, the coastal saline-alkali land of Hebei Province was selected as the research object, and the Maying Village of Nandagang Industrial Park, located in Cangzhou City, was selected as the test base. An experiment of shallow mild saline water irrigation of winter wheat was conducted to analyze the effects of saline irrigation on winter wheat yield and soil salt content. The results indicated that:1) mild saline water irrigation in the joint to heading stage of winter wheat increased the yield of winter wheat in the coastal saline-alkali land of Hebei Province, which was more than 1.5 times that of dry wheat. 2) Based on the subsurface drainage system, mild saline water irrigation did not cause salt accumulation in the soil surface layer. When the rainfall was maintained at multi-year average rainfall level in the rainy season, the average soil salt contents after the 2016−2018 rainy seasons was 2.86, 1.60, and 1.38 g∙kg⁻¹, and the degree of soil salinization was reduced year by year after two consecutive years of salt water irrigation. Shallow saline water resources in the coastal saline-alkali land of Hebei Province can be safely utilized to irrigate winter wheat. Based on this, we considered the coastal region of Cangzhou City of Hebei Province as an example. The analysis of shallow salt water resource prospects showed that: only winter wheat water demand was considered in Cangzhou City, irrigation water demand deficit was at least 1.7 × 10⁸ m³. The shallow saline water resources of 1−5 g·L⁻¹ in Cangzhou City are abundant, meeting the deficit in terms of water resources. The feasibility of mild saline water irrigation for winter wheat makes the planting mode of one crop of spring maize a year in some cultivated land change to the planting mode of two crops of winter wheat-summer maize a year. The sown area of winter wheat can be increased by at least 131 000 hm² in Cangzhou. The results provide a scientific basis for the safe utilization of mildly saline coastal water resources, guaranteed grain yield, and sustainable soil development in the coastal area of Hebei Province.