#UNSWSoilScienceCentral2019: My Top 3
1. Always keep hardly working
2. Help the team and learn from the team
3. Always think positively, be patient and keep the faith
Digital regolith mapping of soil salinity across the Toobeah irrigation area using electromagnetic induction data and inversion modelling
In many irrigated areas of the world, the specter of soil salinisation is an ever-present risk given the prevalence of its occurrence; past and present. One of the main reasons has been the mobilization of stored soluble salts. Information about the areal distribution of salts is therefore necessary to assist policy analysts to understand where salt is stored in a landscape. To map salt, or the soil electrical conductivity of a saturated soil paste extract (ECe – dS/m), we demonstrate how electromagnetic (EM) induction data from a reconnaissance survey of EM38 and EM34 instruments can be used with EM inversion software (EM4Soil). This is because the collected apparent electrical conductivity (ECa – mS/m) data can be inverted to estimate the true electrical conductivity (s – mS/m) and correlated with ECe. In the first instance, we make a quasi-two-dimensional (Q-2D) model, which we use to develop a linear regression (LR) relationship between s and ECe collected from 7 soil sample locations and to a depth of 12 m, along a single transect. The LR was of the form ECe = -0.055 + 0.012 x s with a good correlation coefficient (R2 = 0.61). The second aim was to use the LR to predict ECe from the inversion of interpolated EM38 and EM34 ECa across 40,000 ha. A validation set of ECe, collected from 37 soil sample locations, indicated good concordance (Lin’s = 0.77). We conclude the approach provides useful information on a reconnaissance scale and indicates where more detailed information may be collected to confirm areas of moderate salinity. To better resolve the areal short scale variation, more ECa data should be collected. To improve resolving the depth of clay and ECe data from an EM31 or a DUALEM-421 instrument could also be collected and used in inversion modelling.
Supervisor: Associate Professor John Triantafilis
Distribution of predicted soil salinity (ECe - dS/m) across the Toobeah irrigation area in a 3-D dimension