Salinization characteristics and its determinants of cultivated and uncultivated lands in the Hetao Irrigation District

【Objective】 Hetao Irrigation District is one of the largest irrigation districts in Northwestern China. However, the imbalance between irrigation and drainage has resulted in soil salinization. The purpose of this paper is to investigate the characteristics of soil salinization in both planted and uncultivated soils in this region, as well as the key environmental factors that influence soil salinization. 【Method】 Field investigation and laboratory test were conducted to analyze the ion characteristics and its influential factors in cultivated and uncultivated soils. 【Result】 In the studied area, the predominant anion in both cultivated and uncultivated soils was chloride (Cl-), comprising 59.31% and 58.48% of the composition, respectively. The primary cations were potassium (K+) and sodium (Na+), accounting for 71.32% in cultivated soils and 72.64% in uncultivated soils. Correlation analysis showed that, in cultivated soils, K+ and Na+ were most correlated with sulfate (SO42-) with a correlation coefficient of 0.87, followed by with Cl-, with a correlation coefficient of 0.66; they were least correlated with HCO3-. In the uncultivated soils, K+ and Na+ were mostly correlated with Cl-, with a correlation coefficient of 0.93, followed by with SO42-, with a correlation coefficient of 0.73. Key factors affecting salinization in the cultivated soils included SO42-, magnesium (Mg2+), Cl-, K+ and Na+, while in the uncultivated soil, they were SO42-, Cl-, K+, Na+ and HCO3-. Redundancy analysis showed that salt ions and environmental factors accounted for 13.56% and 20.23% of the variation in salinization in cultivated soils, and 35.17% and 46.17% in salinization in cultivated soils, respectively. Groundwater quality affected soil salt ions the most, followed by soil texture. 【Conclusion】 Soil salinization in both cultivated and uncultivated soils is severe, with Cl-, K+, Na+ and SO42- being the dominant ions. Effective strategies to mitigate soil salinization should focus on improving groundwater quality and optimizing soil texture.