Principle and practice of saline-alkali soil improvement via subsurface pipe engineering in coastal areas of East Hebei Province

Coastal saline-alkali soils form a critical component of the abundant saline soils in China. Shallow groundwater, highly saline soils and strong seasonal changes in soil water and salt are the main characteristics of saline coastal plains in East Hebei Province. Given these characteristics, salt stress, drought and water logging have been the main limiting factors to crop production in this area. This study summarized the principles and implementation of various farmland eco-engineering methods to overcome these limiting factors. It studied the improvements in saline soils via eco-engineering using sensitivity analysis of three kinds of stresses in local common crops in Nandagang. The results of the field experiment showed that yields of cotton and maize were respectively 2.23~3.98 t·hm^-2 and 4.6~6.7 t·hm^-2, which were close to the average level for local farmlands. Total wheat-corn yield at harvest was 9.6~10.8 t·hm^-2 and the yield of wheat-millet reached 9.1~11.9 t·hm ^-2. Farmland eco-engineering significantly increased the suitability land for cropping and multiple crop rotation systems. However, single eco-engineering technology showed some limitations, for example, iced salt-water irrigation increased soil salinity and underground pipe system reduced soil nutrient content and effectiveness. Eco-engineered farmlands were systematic and circulative so that it enhanced redistribution of soil water, reduced soil salt content and prevented salt/water stress. However, there was still the need for more functional technologies to adjust crop to environment for optimal yield. Eco-engineering aimed at producing high crop yields and balanced soil salt content. For that purpose, underground pipe systems replaced the open-ditch systems as the basis of drainage and eco-engineering. Furthermore, eco-engineering was gradually becoming abundant, systematic in the saline-alkaline farmlands of East Hebei Province.