Salinity monitoring in reclaimed marsh soils with electromagnetic induction tomography and and NDVI imagery

Abstract

The presence of a shallow saline water table in combination with intensive agriculture in the reclaimed marshes of the B-XII irrigation district, in SW Spain, may disrupt the fragile balance between salt accumulation and leaching in the root zone. We evaluate the potential of electromagnetic induction tomography (EMI) and the use of Sentinel 2 NDVI imagery for field-scale soil salinity monitoring using soil apparent electrical conductivity (ECa) measured in 2017 and 2020. Depth-specific electrical conductivity (EC), obtained from the inversion of ECa, showed a strong correlation (R≈0.90) with laboratory-analysed saturated paste extract conductivity (ECe) and sodium adsorption ratio (SAR), resulting in linear calibration equations with R²≈0.80 for both years and reliable cross-validation of exclusion (LOOCV) results for the subsoil (0.55 < R² < 0.81). The spatial pattern of EC showed inverse correlation with NDVI for processed tomato, cotton and sugar beet, cropped between 2017 and 2019, reaching R values of -0.64, -0.87 and -0.73, respectively.