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Glossary of terms used throughout the printed publication and this online version.



EC (electrical conductivity)

The ability of a substance to conduct electricity. In soil, EC is a measure of the electrical current conducted by water and soil. EC is the most convenient method to measure soil or water salinity. It is commonly expressed in decisiemens per metre (dS/m). EC readings are affected by the concentration and composition of dissolved salts, so high EC values do not always mean high salinity values.


Electrical conductivity measured in a soil solution of one part of soil and five parts of deionised water. EC1:5 is the most commonly used method to estimate soil salt content.


Apparent electrical conductivity. A measure of bulk electrical conductivity of undisturbed soil in the field. ECa can be measured with an electromagnetic instrument (EM38 or EM31).


Electrical conductivity of a saturated soil. This is the most accurate measure of soil salt content and can be estimated by multiplying the EC1:5 by a conversion factor based on the soil texture group.


An electromagnetic induction instrument used to measure bulk ECa in the field. Readings from an EM38 instrument are sensitive to soil water content, soil texture and metal. They therefore require local calibration against electrical conductivity (ECe) measurements from a laboratory before use.


ECa value obtained when reading EM38 value in the horizontal mode. This is sensitive to soil salinity at the 0–0.35 m depth zone.


ECa value obtained when reading EM38 value in the vertical mode. The EMv value is sensitive to soil salinity at the 0.35–1.5 m depth zone.

exchangeable sodium percentage

The amount of sodium in the soil solution relative to the amount of total cations in the same solution; often used as an indicator of soil sodicity. A soil is considered sodic when the exchangeable sodium percentage is 6% or greater. Soil dispersion problems may occur at a higher or lower level than this, depending on clay type.


Non-rice food crops such as soybean, mungbean, peanut or maize grown on lowland rice fields during the dry season in Indonesia.


The acidity or alkalinity of a solution, measured by the activity of dissolved hydrogen ions (H+), on a scale of 1–14 (7.0 is neutral pH); most agricultural soils are in the pH range of 4.5–8.

sodic soils

Also referred to as dispersive soils. The chemical composition of sodic soils makes them more likely to dissolve when exposed to water and more vulnerable to erosion.

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