Objective The aim was to develop a simplified indicator system for efficiently evaluating soil quality in saline-alkali farmland in Shanxi Province.

Method Taking saline-alkali farmland in Ying County, Shanxi Province as the research object, sampling sites were uniformly distributed within the county, soil samples were collected, and relevant soil physical and chemical indicators were measured. A combination of principal component analysis and correlation analysis was used to construct a minimum data set (MDS) for soil quality evaluation. The soil quality index (SQI) was calculated using the membership function method, and geostatistical methods were employed to analyze the spatial distribution characteristics of the SQI. Finally, an obstacle factor diagnostic model was used to identify the key limiting factors affecting soil quality.

Result The bulk density, soil organic matter, pH, exchangeable sodium, available phosphorus and available potassium were screened to set an MDS for soil quality evaluation. The SQI of the total dataset (TDS) was significantly positively correlated with MDS-SQI (P < 0.001, R = 0.91), indicating that MDS could replace TDS for soil evaluation. The SQI ranges of cultivated land in Ying County were 0.22 ~ 0.93, showing a gradually increasing trend from northwest to southeast in space. Among them, the SQI of cultivated land near the Sanggan River Basin in the northwest was generally low, and soil salinization was severe. The main limited factors of farmland soil in Ying County were available phosphorus, cation exchange capacity, soil organic matter, pH and total nitrogen.

Conclusion For the severely saline-alkali areas in the northwestern part of Ying County, it is recommended to apply organic fertilizers and physiologically acidic inorganic fertilizers to improve soil structure and inhibit the development of salinization. In the central and eastern regions, the focus should be on enhancing soil fertility, which can be achieved by applying organic fertilizers and promoting straw return to the fields. The research results provide a scientific basis for evaluating the soil quality of saline-alkali farmland in Shanxi Province.