Table 1. Comparison of variations in electrical conductivity measurement.

Common Name	Common Abbreviation(s)	Soil to Water Ratio	Brief Description	Common Complicating Factors	Methodological influence on measured EC
Soil Water Extract	None	Variable	Water is extracted from the soil in the field by applying a vacuum to a soil surface. Soil water flows under pressure to a collection cup for measurement.	field moisture content, temperature	Ion concentration and resulting measured EC dependent upon field water content at the time of observation. Good for measuring temporal change in local EC, but not possible to compare measurements between overall locations. Conductivity increases 1.9% for every degree centigrade of increased temperature [61], and is often done at 25°C in laboratory settings. Many modern devices auto calibrate reported EC measurement based on a simultaneously measured temperature, but the specific device should be stated.
Extract of Saturated Paste	ECe; ECse; ECSP	Variable	Water is mixed with soil until it reaches saturation, and then this moisture is extracted under a vacuum from the solid soil. Amount of water used is dependent upon soil texture, and a general expectation is to recover 1/3 of added water upon extraction.	technician experience, saturation percentage variation, equilibration time, temperature	Method requires technician interpretation of qualitative attributes in sample production and is susceptible to variation based on experience. Insufficient equilibration time may result in an underestimation of EC.
Aqueous Mixture; Soil to Water Dilution	EC1:1	1:1	A given mass of soil is mixed with its equivalent volume of water. E.g. 10 grams of soil with 10 ml of water for a 1:1 ratio. It is then allowed to sit, often with occasional stirring, in order for the solution to equilibrate. Equilibration time, stirring method, and dilution ratio can be highly variable between studies.	equilibration time, extraction under vacuum versus direct measurement on soil to water mixture, dried & disaggregated sample versus ground sample, temperature	The concentration of ions in solution will decrease with higher dilution ratios and result in a lower measured EC. Direct measure of soil-water mixture will include conductivity due to clays whereas conductivity of an extract will be of ions alone. Insufficient of equilibration time may result in an underestimation of EC. This may be counteracted by grinding the sample, and thus increasing total surface area for dissolution, but may also increase hydrolysis of minerals and contribute to an artificial increase in EC.
	EC1:2	1:2
	EC1:2.5	1:2.5
	EC1:5	1:5