Methodologies and the Practical Aspects of the Bulk Soil EC (σa)—Soil Solution EC (σw) Relations

The total concentration of ions present in a solution is a useful indicator for salinity in fields like hydrology, environment, industry, and agriculture. Salinity evaluation in agricultural activity may be connected to research and application processes: osmotic pressure, leaching, water bodies mixing, irrigation management, water pricing, and water allocation. An immediate and simple means for salinity level evaluation is the measurement of the soil (or any other porous media) electrical conductivity (σ a ). Until the TDR‐era, σ a and soil volumetric water content (θ) were measured by two separate techniques and inevitably not in the very same spot. The introduction of TDR into soil science enabled the measurement of these two soil properties in exactly the same volume, with the highest accuracy. Moreover, pre‐TDR calculation models could be readopted and applied to handle the newly obtained data. This review voluntarily confines itself to the practical aspects of accurately converting σ a into σ w for different soil types, moisture levels, and solution chemical compositions. Subsequently, a short background description of pre‐TDR measurement methods and calculation techniques and the basics of TDR methodology are presented, and three procedures for σ a calculations are discussed, of which the Giese‐Tiemann stands out as the most recommended. Special attention is given to the once popular Dalton et al . (1984) model. Following are nine presented and compared protocols suggesting ways to evaluate σ w from σ a, θ, and soil properties. Light is thrown on the extent and significance of the curvilinearity of the σ a – σ w relations for σ w −1 . The conclusions sum up those field situations deserving special care along with ideas about further research needed to increase acceptance of the TDR technology for monitoring salinity by farmers. As always, we should remember with respect the contribution of the previous generations (Cremers, Sauer, Spiegler, Laudelout), whose deep theoretical understanding and originality were their main tools for laying the foundations for the better‐equipped generation that followed to put their ideas into practice.