What information does the electrical conductivity of soil water extracts of 1 to 5 ratio (w/v) provide for soil salinity assessment of agricultural irrigated lands?

Monitoring and evaluating spatial variability of soil salinity in dry and wet seasons in the Werigan–Kuqa Oasis, China, using remote sensing and electromagnetic induction instruments

“…The averages of the electrical conductivity and salinity of these points are used as the base values for the sampling site. EC 1:5 and salinity are usually highly correlated and EC 1:5 is often used as a surrogate for soil salinity (Visconti et al, 2010;Zhang et al, 2009b). This is indeed the case in our current study.…”

Evaluation of 1:5 soil to water extract electrical conductivity methods

“…For example, in soils containing gypsum or calcite, the amount of calcium and sulfate that are dissolved can increase when the amount of water used in extraction is increased, while the concentration of the other ions such as chloride can decrease due to dilution since chloride salts are likely pre-dissolved due to their relatively high solubility (Al-Mustafa and Al-Omran, 1990;FAO, 1973;Hogg and Henry, 1984;Robbins and Wiegand, 1990). In addition, the presence of gypsum can decrease the relationship between EC e and EC 1:5 at EC 1:5 values greater than 1.5 dS m − 1 (Visconti et al, 2010). Salt dissolution may also be affected by biological activities in solution due to a reduction in diffusion of salts from particle interiors due to the presence of biofilms (VanderGheynst et al, 2004).…”

“…For example, the standard 1:5 method used in Australia is by mechanically shaking the required amount of soil sample (20 g) and deionized water (DI) (100 mL) for 1 h, followed by 20-30 min of undisturbed settling before measurement of EC (Rayment and Higginson, 1992). Other 1:5 procedures include agitation methods of shaking, and stirring, and agitation times between 20 min and 24 h (Chi and Wang, 2010;USDA, 1954;Visconti et al, 2010) followed by undisturbed settling, centrifuging, or filtration prior to EC measurement (Al-Mustafa and Al-Omran, 1990;Chi and Wang, 2010;Hurrass and Schaumann, 2006;Khorsandi and Yazdi, 2007;Loveday, 1974;Marion et al, 1991;Notario del Pino et al, 2008;Rayment and Higginson, 1992;Rhoades, 1982;USDA, 1954;Visconti et al, 2010). Detailed information about agitation methods and times used in studies from different countries are shown in Table 1.…”

Management implications inferred from the multivariate analysis of vadose zone chemical variables in Las Tablas de Daimiel National Park (Spain)

“…Median values in this layer (49 mg/l for nitrate and 19.5 mg/l for potassium) are half of those found by Visconti et al (2009) in saturation extracts from fertirrigated soils in the SE of Spain (99.2 mg/l for nitrate and 35.1 mg/l for potassium). Even though many empirical equations have been developed to predict the properties of saturation extracts, primarily electrical conductivity, from the properties of 1:5 soil-water extracts, there are not universally valid equations relating concentrations from both methods (Visconti et al, 2010). However it can be assumed that they would be higher in saturation extracts than in soil-water solution as found by the same authors for electrical conductivities.…”