Study on the adaptability and potential application effects of subsurface pipe drainage system in the coastal areas of Hebei Province

About 8.6×105 hm2 saline/alkaline lands exist in the coastal areas of Hebei Province. Soil salinity in the coastal areas of Hebei Province has mainly been caused by shallow groundwater table and highly saline groundwater. Remedial solutions to soil salinity/alkalinity were by deepening water tables in the region. Subsurface pipe drainage system has proved effective in deepening water tables in the coastal areas of Hebei Province. To research into the effects of subsurface pipe drainage system on soil salinity/alkalinity in the coastal areas of Hebei Province, regions suitable for application of subsurface pipe drainage system were delineated. The research analyzed the limiting conditions of subsurface pipe drainage system application. The superposition and other analyses were executed in ArcGIS environment. The aim of subsurface pipe drainage system was to reduce soil salinity/alkalinity and increase the fertility of saline/alkaline lands. As the coastal areas of Hebei Province is an important grain production region, it is critical to study the effects of subsurface pipe drainage system on optimizing land output. In the paper, the summer maize-winter wheat, foxtail millet-winter wheat and monoculture cotton cropping systems were analyzed. Haixing County, a county with typical saline/alkali soils, was selected as the study area to calculate the changes in ecological services value (ESV) caused by the use of subsurface pipe drainage system. The results were as follows: 1) the region suitable for the application of subsurface pipe drainage system was 3.90×105 hm². In the 3.90×105 hm², the areas of original arable lands, ditches and wastelands were 3.21 ×105 hm², 5.14×104 hm² and 1.76×104 hm², respectively. So the new arable land area after subsurface pipe drainage system application was 6.90×104 hm². (2) Based on arable land area after subsurface pipe drainage system application and real cultivation area ratios of different crops, yield of summer maize-winter wheat increased by 4.82×10⁸ kg, yield of foxtail millet-winter wheat increased by 1.29×10⁸ kg and yield of monoculture cotton increased by 3.67×10⁸ kg. (3) In Haixing County, ESV increased by 3.90×10⁹ Yuan·a 1 after application of subsurface pipe drainage system. On average, ESV increased by 4.06×10⁴ Yuan·hm^-2·a^-1.