Comparison of Electromagnetic Induction and Electrical Resistivity Tomography in Assessing Soil Salinity: Insights from Four Plots with Distinct Soil Salinity Levels

Maria Catarina Paz, Nádia Luísa Castanheira, Ana Marta Paz, Maria Conceição Gonçalves, Fernando Monteiro Santos and Mohammad Farzamian ()
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Maria Catarina Paz: RESILIENCE—Center for Regional Resilience and Sustainability, Escola Superior de Tecnologia do Barreiro, Instituto Politécnico de Setúbal, Rua Américo da Silva Marinho, 2839-001 Barreiro, Portugal
Nádia Luísa Castanheira: Instituto Nacional de Investigação Agrária e Veterinária, Avenida da República, Quinta do Marquês (Edifício Sede), 2780-157 Oeiras, Portugal
Ana Marta Paz: Instituto Nacional de Investigação Agrária e Veterinária, Avenida da República, Quinta do Marquês (Edifício Sede), 2780-157 Oeiras, Portugal
Maria Conceição Gonçalves: Instituto Nacional de Investigação Agrária e Veterinária, Avenida da República, Quinta do Marquês (Edifício Sede), 2780-157 Oeiras, Portugal
Fernando Monteiro Santos: Instituto Dom Luiz, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, Edifício C1, Piso 1, 1749-016 Lisboa, Portugal
Mohammad Farzamian: Instituto Nacional de Investigação Agrária e Veterinária, Avenida da República, Quinta do Marquês (Edifício Sede), 2780-157 Oeiras, Portugal

Land, 2024, vol. 13, issue 3, 1-17

Abstract: Electromagnetic induction (EMI) and electrical resistivity tomography (ERT) are geophysical techniques measuring soil electrical conductivity and providing insights into properties correlated with it to depths of several meters. EMI measures the apparent electrical conductivity (EC a , dS m −1 ) without physical contact, while ERT acquires apparent electrical resistivity (ER a , ohm m) using electrodes. Both involve mathematical inversion to obtain models of spatial distribution for soil electrical conductivity (σ, mS m −1 ) and electrical resistivity (ρ, ohm m), respectively, where ρ is the reciprocal of σ. Soil salinity can be assessed from σ over large areas using a calibration process consisting of a regression between σ and the electrical conductivity of the saturated soil paste extract (EC e , dS m −1 ), used as a proxy for soil salinity. This research aims to compare the prediction abilities of the faster EMI to the more reliable ERT for estimating σ and predicting soil salinity. The study conducted surveys and sampling at four locations with distinct salinity levels in Portugal, analysing the agreement between the techniques, and obtained 2D vertical soil salinity maps. In our case study, the agreement between EMI and ERT models was fairly good in three locations, with σ varying between 50 and 500 mS m −1 . However, this was not the case at location 4, where σ exceeded 1000 mS m −1 and EMI significantly underestimated σ when compared to ERT. As for soil salinity prediction, both techniques generally provided satisfactory and comparable regional-level predictions of EC e , and the observed underestimation in EMI models did not significantly affect the overall estimation of soil salinity. Consequently, EMI demonstrated an acceptable level of accuracy in comparison to ERT in our case studies, supporting confidence in utilizing this faster and more practical technique for measuring soil salinity over large areas.

Keywords: electromagnetic induction; electrical resistivity tomography; soil salinity (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2024
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