Soil salinization is directly related to the quantity and quality of food production, and often, to increased energy demands for high-quality irrigation water. Reliable monitoring of soil salinity based on a less laborious method than the soil saturated paste (SP) extract methodology is required. In the present study, an attempt is made to relate the electrical conductivity (EC) of the soil saturated paste (SP) extract (EC_e) with the EC determined in the 1:1 and 1:5 soil over water mass ratios, (soil:water) extracts (EC_1:1 and EC_1:5). EC_e, EC_1:1, and EC_1:5 values were obtained for 198 soil samples from five different locations in Greece. The results have shown that strong linear relationships exist between the EC_e and the EC_1:1 and EC_1:5 values (R² > 0.93), and that the slopes of these linear relationships decreased from coarse to fine soil types. For 123 soil samples, the concentrations of Κ⁺, Νa⁺, Ca²⁺, Mg²⁺, and Cl⁻ were also determined in the extracts of the three applied methodologies. Ion concentrations in the 1:1 and 1:5 extracts were highly correlated with the respective ion concentrations in the SP extracts. These findings strongly suggest that EC_1:1 and EC_1:5 values can be safely used for the estimation of EC_e.

The salinity status of soil can be obtained through the measurement of the pore-water electrical conductivity σp . In the present study the WET sensor’s capability in predicting σp through the simultaneous measurements of the soil bulk electrical conductivity ( σb ) and the soil dielectric constant (K) is investigated. The estimation of σp is based on a model by Hilhorst, which relates σp to the two other quantities K and σb and an extra fitting parameter K0 which is incorporated in the software of the device. The study involved experimental measurements in the laboratory using four different soils with a large range in soil texture and volumetric water content θ . In each soil type four different electrical conductivity aqueous solutions were used. The results exhibited a rather strong linear relationship between K and σb . The slope of this linear relationship appeared to depend on both the soil type and the electrical conductivity of the pore water. The value of K0 seems to be soil specific and increas...

The standard methodology for the soil salinity assessment is provided through the determination of the electrical conductivity (EC) of the soil saturated paste extract, EC_e. This approach is cumbersome and tedious. Instead of this, it appears easier to measure the EC of various soil over water mass ratios, (soil:water), such as 1:1, 1:5. In the present study an attempt is made to compare the EC_e methodology with the methods providing the EC_1:1 and EC_1:5. EC_e, and EC_1:1 or EC_1:5 values were obtained from 198 soil samples from 5 different locations in Greece. It was shown that the methods providing EC_1:1 and EC_1:5 values are linearly correlated to the EC_e methodology with a high correlation coefficient (R² > 0.93).

Although soil water redistribution is critical for a number of problems, a rather limited study of this process has been reported up to now and especially as regards the implications of hysteresis on horizontal soil water redistribution after infiltration. To this end, a thorough theoretical and numerical investigation of the redistributed soil water content profiles formed after the cessation of a horizontal infiltration is presented. A number of different initial soil water contents before the initiation of the horizontal infiltration and different infiltration depths were analyzed using the HYDRUS-1D software package considering the appropriate hysteretic wetting and drying curves. The effect of neglecting hysteresis was also investigated for the same conditions. The main wetting and drying boundary curves of the studied porous medium and the hydraulic conductivity at saturation were experimentally determined. The theoretical and numerical analysis indicated that the form of the redistributed soil water content profiles in the presence of hysteresis was similar to the original infiltration profile independently of whether the initial soil water content was taken on the boundary wetting or drying curve and independently of the porous medium type. Specifically, in a relatively short time after the initiation of the redistribution process, the magnitude of the soil matrix head gradient tended to zero due to hysteresis, and this resulted in an insignificant soil water movement, although the soil water content and the hydraulic conductivity values were still high. In addition, the redistribution proceeded at a faster rate than the smallest depth of infiltration water prior to the redistribution, and it was faster during the early stages of the redistribution. Accordingly, hysteresis is important for the simulation of horizontal soil water redistribution as it is, for example, in the case of localized irrigation systems’ design and management.