Interpreting method of regional soil salinity 3D distribution based on inverse distance weighting

Abstract: In order to clarify the three-dimensional spatial pattern of soil salinity on a regional scale, the Inverse Distance Weighting (IDW) method was used, combining the electromagnetic induction technique in this study. Apparent electrical conductivities were measured by electromagnetic induction, and thus layered salinity interpreting models with reasonable accuracy were established. The models showed a significant correlation between soil salt contents of different layers and apparent soil conductivities measured by electromagnetic induction, while soil moisture and clay content also significantly correlated with the apparent soil electrical conductivities. According to the classical statistical results, the minimum values (0.742-0.821 g/kg) of soil salt contents in different soil layers were substantially equal, but the maximum values differed from 5.943 to 9.810 g/kg, showing a significantly increased regularity with increasing depth, and the average values varied from 2.3 to 3.0 g/kg. Soil salinities of every layer belonged to moderate variability while the coefficients of variation increased with the increase of soil depth. Three-dimensional spatial distribution of soil salinity was characterized by IDW. Regional soil salinity spatial distribution characteristics were intuitively revealed by three-dimensional graphics. Profile soil salinity varied greatly with depth, showing different types of profile distribution characteristics in different locations across the study area. Soil of the main study area registered moderate or severe degree of salinization, which showed that there were more common and severe soil salinization in this study area. The 3D inverse distance weighting method combined apparent soil conductivity rapid determination by means of electromagnetic induction, and could achieve exact analytical evaluation of the three-dimensional spatial variability of regional soil salinity. This study and the results could provide a reliable technical method for interpretation and evaluation of regional soil salinity in the three-dimensional spatial distribution characteristics.