Estimation of soil salinity in a drip irrigation system by using joint inversion of multicoil electromagnetic induction measurements

Abstract

Low frequency electromagnetic induction (EMI) is becoming a useful tool for soil characterization due to its fast measurement capability and sensitivity to soil moisture and salinity. In this research, a new EMI system (the CMD mini-Explorer) is used for subsurface characterization of soil salinity in a drip irrigation system via a joint inversion approach of multiconfiguration EMI measurements. EMI measurements were conducted across a farm where Acacia trees are irrigated with brackish water. In situ measurements of vertical bulk electrical conductivity (r b ) were recorded in different pits along one of the transects to calibrate the EMI measurements and to compare with the modeled electrical conductivity (r) obtained by the joint inversion of multiconfiguration EMI measurements. Estimates of r were then converted into the universal standard of soil salinity measurement (i.e., electrical conductivity of a saturated soil paste extract -EC e ). Soil apparent electrical conductivity (EC a ) was repeatedly measured with the CMD mini-Explorer to investigate the temperature stability of the new system at a fixed location, where the ambient air temperature increased from 26 C to 46 C. Results indicate that the new EMI system is very stable in high temperature environments, especially above 40 C, where most other approaches give unstable measurements. In addition, the distribution pattern of soil salinity is well estimated quantitatively by the joint inversion of multicomponent EMI measurements. The approach of joint inversion of EMI measurements allows for the quantitative mapping of the soil salinity distribution pattern and can be utilized for the management of soil salinity.

Improved Geoarchaeological Mapping with Electromagnetic Induction Instruments from Dedicated Processing and Inversion

“…The approach by Santos was lately developed further to a quasi-3D approach, but still under the LIN approximation [23]. Other studies have also aimed at deriving the layering of the subsurface while assuming the LIN-approximation [24][25][26]. However, even if the LIN approximation is easy to use and implement, there has been a consistent use of the direct measurement values (typically converted to apparent conductivity or resistivity) as the final product [11,27,28].…”

Inferring soil salinity in a drip irrigation system from multi-configuration EMI measurements using adaptive Markov chain Monte Carlo

“…Ten pits were dug along the same transect and in each pit the bulk electrical conductivity σ b profile was measured at 15 locations within a depth range of 0.05-1.5 m via 5TE capacitance sensors (Decagon Devices, Pullman, USA). EMI and 5TE measurements were performed 8 h after the drip irrigation system was stopped, so that the soil moisture is not concentrated below the drippers and to give enough time to reduce the soil moisture impact due to evaporation, root water uptake, and infiltration (Jadoon et al, 2015). Figure 2a and b depict the observed, estimated (modeled) and range of EC a as they result from the chain of MCMC simulation for six configurations of the synthetic case with saline and non-saline soil.…”

“…Furthermore, for the six tested configurations of Figure 5. (a) Electrical conductivity (mS m −1 ) measured by the 5TE capacitance sensors from 10 soil pits along transect and the location of the soil pits is indicated by black triangles (Jadoon et al, 2015); (b) the soil electrical conductivity obtained by using Markov chain Monte Carlo simulation for multi-configuration electromagnetic induction measurements. CMD Mini-Explorer, the HCP and VCP configuration with spacing 1.18 m are mostly sensitive to the consolidated layer while the remaining four configurations are more sensitive to the upper horizon.…”

“…For decades, the development and use of quantitative EMI inversions were mainly hampered by the lack of efficient calibration methods; von Hebel et al (2014) used electrical resistivity tomography to calibrate EMI measurements before inversion to estimate three-dimensional images of subsurface electrical conductivity. Recently, Jadoon et al (2015) calibrated EMI measurements via vertical electrical conductivity profile measured by capacitance sensors in different pits and later performed inversion for calibrated multi-configuration EMI measurements to estimate the effect of soil salinity distribution in an acacia tree farm.…”

Application of Electromagnetic Induction to Monitor Changes in Soil Electrical Conductivity Profiles in Arid Agriculture

“…The use of EMI is largely motivated by the need of robust and compact system design, easy to use, rapid acquisition, and capability to produce a large number of georeferenced measurements that can be associated with the spatial variability of subsurface at the field scale (Corwin, 2008). Several inversion algorithms have been developed for EMI measurements to improve the resolution of subsurface features and the assessment of soil properties (Hendrickx et al, 2002;Lavoue et al, 2010;Triantafilis and Monteiro Santos, 2013;Jadoon et al, 2015). Generally these inversion algorithms are robust and provide useful estimates of subsurface properties in terms of optimal model parameters, analysis of parameter uncertainty and correlation is often left unaddressed.…”