Spatio-temporal Mapping of Soil Salinity Using Joint Inversion of Time-lapse Multi-coil and Multi-heights Electromagnetic Induction Measurements

Soil salinization limits agricultural productivity and can ultimately cause desertification and land abandonment. It is important to assess the spatio-temporal variability of the soil's salinity in order to understand the processes controlling salinization. Soil salinity is traditionally assessed using soil sampling methods for laboratory determinations which are not representative of soil properties at management scale and are highly time and work consuming, resulting in costly surveys.

Electromagnetic Induction (EMI) method is becoming a strong tool for soil salinity and water content assessment due to its fast and cost-effective measurements. In the scope of SALTFREE project, we are using EMI technique in four countries around the Mediterranean - Portugal, Italy, Egypt, and Tunisia- in order to study the salinization risks in different Mediterranean production systems.

We have evaluated the potential of time-lapse multi-coil and multi-heights EM measurements and joint inversion approach in time-lapse soil salinity mapping under different conditions (e.g. soil types, irrigation management, crop). Our study shows that the joint inversion of EMI measurements allows for the quantitative mapping of the soil salinity variation in time and space and can be used for the management of soil salinity. The method may also be used for hydrogeophsical approach in order to estimate the soil's hydraulic parameters at management scale.

Acknowledgements

This work was developed in the scope of SALTFREE project (ARIMNET2/0005/2015 SALTFREE). Publication is supported by the project FCTUID/GEO/50019/2013-Instituto Dom Luiz