Spatial and temporal heterogeneity of soil salinity and ionic coupling relationship under the water-saving renovation of a typical irrigation district in arid and semi-arid areas

Soil salinization is a global environmental problem. To investigate the spatiotemporal heterogeneity of soil salinity and the coupling relationship of soil salinity ions under water-saving renovation conditions, we chose Shenwu Irrigation Area, where water-saving renovation projects are being conducted comprehensively. Specifically, for our field experiments, we chose 46 soil sampling points. Specifically, we used different spatial interpolation methods and coupling coordination models were applied to study the spatial and temporal distribution of soil salinity and soil salt-based ion coupling relationship changes during different water-saving periods in the irrigation area between 2015 and 2022. The results showed that (1) the emergence of soil salinity extremes after water-saving renovation project led to an increase in the variability of soil salinity. (2) Compared with the Inverse Distance Weighted, Radial Basis Function, and Universal Kriging interpolations, the Mean Absolute Error of the Ordinary Kriging interpolation was reduced by 12.68 %, 43.96 %, and 38.77 %, the Root Mean Square Error was reduced by 14.34 %, 60.85 %, and 36.53 %, reflective of a significant improvement in accuracy, and thus confirming this method to be optimal for elucidating soil salinity. (3) Compared with pre-water-saving renovation project, the average soil desalination rates in the 0–50 cm soil layer during and after project implementation were 5.71 % and 35.67 %. The impact of the water-saving renovation project was highest in channelside areas, followed by croplands, and lowest in lakeside areas. (4) The growth rates of soil salt-based ion coupling degree and coupling coordination degree after project implementation, compared with before implementation, were 17.07 % and 10.81 %. The implementation of water-saving renovation project improved soil quality. This study provides scientific support for the prevention and control of soil salinization in irrigation areas.