An in-situ methodology to separate the contribution of soil water content and salinity to EMI-based soil electrical conductivity

Salt accumulation in the root zone limits agricultural productivity and can eventually lead to land abandonment. Therefore, monitoring the spatial distribution of soil water content and solution salinity is crucial for effective land and irrigation management. However, assessing soil water content and salinity at the field scale is often challenging due to the heterogeneity of soil properties. Electromagnetic induction (EMI) offers a fast, non-invasive, in situ geophysical method to map spatial variability in soil. EMI instruments measure the apparent soil electrical conductivity (ECa), which reflects the integrated contribution of the bulk electrical conductivity (σb) of different soil layers. By inverting the measured ECa, it is possible to obtain the distribution of the σb along the soil profile, which provides indirect information on soil salinity. However, in saline soils, σb is influenced by both water content (θ) and soil solution electrical conductivity (σw) (the salinity), making it difficult to ind