A Study on the Distribution Characteristics of Salinity and Nutrients and the Migration Mechanism of Soil Salt in the Delingha Saline‐Alkali Soil Profile of the Qaidam Basin

ABSTRACT

Soil salinization negatively impacts the economic development and ecological environment, particularly in the arid and semiarid regions of China. The Qaidam Basin constitutes a major distribution area of saline‐alkali land in the country. However, the distribution patterns of salinity and nutrients within soil profiles and the underlying salt transport mechanism remain poorly constrained. Here, through laboratory physicochemical experiments, we determined the soil electrical conductivity, salt ions, nutrient contents, and particle size distribution in the Gahai profile (GHP) saline‐alkali soil (depth: 0–119 cm) of the Qaidam Basin to comprehensively analyze their vertical distribution characteristics. Simultaneously, we employed relevant statistical methods to disclose the relationship between soil nutrients, salt content, and particle size, and to investigate the migration pattern of soil salt ions. The results reveal that the surface soil (0–27 cm) in the GHP profile is severely saline, whereas soil below 27 cm ranges from slightly saline to nonsaline; the entire profile is strongly alkaline. In the surface soil (0–27 cm), the dominant anion is Cl ⁻ , followed by SO ₄ ²⁻ , with Na ⁺ as the primary cation. As the soil depth increases, HCO ₃ ⁻ and Ca ²⁺ become the main salt ions. The nitrogen and organic matter nutrients are deficient, while phosphorus and potassium have relatively high levels. Soil texture is primarily silty loam and sandy loam. Based on the soil salinity movement pattern, the soil profile could be divided into the salt‐ion rising section (0–27 cm) and the equilibrium section (27–119 cm). Accordingly, salt‐suppressing irrigation measures can be implemented initially, followed by deep ploughing to bring the lower‐layer silt loam soil to the surface. This soil salt transport pattern and control measures may only be applicable to the alluvial‐floodplain type of saline‐alkali land in extremely arid basins in northwest China, such as those in Qinghai and Xinjiang provinces. These findings enhance our understanding of the distribution characteristics of salts and nutrients in the saline‐alkali land of the Qaidam Basin, along with its influencing factors and salt transport mechanisms, offering theoretical support and practical guidance for long‐term soil salinization restoration strategies.