Comparison of interpolation approaches based on spatial variability of apparent soil electrical conductivity with an electromagnetic induction

To solve the problem of soil salinization existing in the Yellow River Delta at present, electromagnetic induction EM38 was applied to study the spatial variability of apparent electrical conductivity under various sample densities with the GIS technology and geostatistics method, which was conducted in characteristic field of the Yellow River Delta. The optimized spatial interpolation approach was determined through systematic comparisons, and distortion index(DI) was introduced to evaluate the spatial similarity of apparent electrical conductivity distribution patterns. Results indicate that apparent electrical conductivity data under various sample densities all exhibite moderate spatial variation and follow logarithmic normal distribution, and apparent electrical conductivity under various sample densities all show strong spatial autocorrelation with the spatial variability at the field scale of less than 10 m. As to prediction accuracy, the sequence is universal kriging > ordinary kriging > inverse distance weighed > local polynomial. Distortion index analysis show that the spatial similarity of apparent electrical conductivity distribution patterns all decline with the decrease of sample density. In terms of the extent of spatial information retention under the same sample density reduction, the sequence is universal kriging > ordinary kriging > inverse distance weighed > local polynomial. It means that the sample density can be rationally reduced and prediction accuracy will be maintained with the application of universal kriging. With respect to the field data collection by using electromagnetic induction EM38, the research results can serve as a theoretical and technical reference to the determination of rational sample density and optimized spatial interpolation model in saline soils of the Yellow River Delta.