An Empirical Framework of Washing Salinity by Irrigation to Maintain Soil Quality in Hetao Irrigation District

[Objectives] To summarize the characteristics of washing salinity by irrigation in the Hetao Irrigation District, propose the empirical framework of washing salinity by irrigation to maintain soil quality, and provide a theoretical basis for maintaining the sustainable development of soil in Hetao Irrigation District. [Methods] The methods of experiment, questionnaire, on-the-spot investigation and literature review were used. [Results] This study proposed the empirical framework of washing salinity by irrigation to maintain soil quality in the Hetao Irrigation District. Seven factors of the framework, including flood irrigation, land leveling, plastic film mulching, fertilization, soil organic matter (SOM), pH value, and salinity, and their relationships were determined. The characteristics of these factors in the Hetao Irrigation District were investigated (flooding irrigation with a large amount of irrigation water, high amount of fertilizer application, low organic matter, high pH value, large variation of salinity, etc.). The mechanisms and effects of various factors affecting soil quality in the Hetao Irrigation District were analyzed (the mean SOM and pH value were kept in the range of 10.9-13.9 g/kg and 8.0-8.15 in recent 35 years, respectively, and increased slightly, etc.). [Conclusions] The empirical framework can be used as a theoretical norm for evaluating soil quality under the condition of washing salinity by irrigation. Under the condition of washing salinity by irrigation, the agricultural soil quality in Hetao Irrigation District showed a stable trend over time. Using this framework, we can find soil problems, and adjust some unbalanced factors to maintain the stability of soil quality in the Hetao Irrigation District, and can also provide a reference for other areas.