Management of Salt-Affected Soils - Practices of Irrigation and On-farm Water Management - page 282

8.3.1.3 Saline-Sodic Soil

These soils contain large amounts of total soluble salts and greater than 15%
exchangeable sodium. The pH is generally less than 8.5. Physical properties of these
soils are good as long as an excess of soluble salts is present.

Characteristics:

• Electrical conductivity (EC) is greater than 2 dS/m, showing higher soluble salt

concentration.

•

Exchangeable sodium percentage (ESP) is greater than 15 or, sodium absorption
ratio, SAR value is greater than 13, indicating high level of exchangeable sodium.

• The pH value of this soil is generally less than 8.5.

Dispersion will occur in soils having excess sodium and relatively low Ca and
Mg. As a result of clay dispersion, soils will have poor physical properties. This
results in a massive or puddled soil with low water infiltration, poor tilth, and surface
soil crust formation.

8.3.2 Some Relevant Terminologies and Conversion Factors

Salts : Soluble mineral substances present in soil, rocks, groundwater, and sur-
face water. The salts most commonly occurring in soil are common salt (for
example, sodium chloride - NaCl), gypsum, and lime.
Ions : Charged elements that join to form different salts, e.g., sodium ions (Na + )
and chloride ions (Cl - ) form sodium chloride (NaCl) or common table salt.
Soluble salts : Major dissolved inorganic solutes.
Salt loads : The amount of salt generated in the dryland area.
Salt scalds : Salty subsoils that have been exposed by wind erosion.
Saline groundwater : Groundwater containing dissolved salts.
Dryland salinity : All areas of salinity where irrigation is not present.
Ion specific effects : Effect of different ions, e.g., chloride (Cl - ), sodium (Na + ),
Iron (Fe), or boron (B) on plants.
Salinity control regions : For the management of salinity, a State may be
divided into several regions. The boundaries may be drawn up taking into
account salinity provinces, catchment boundaries and other administrative
boundaries.
Salinity mitigation : Any activity which reduces the salinity problem. For
example, re-vegetation, improved cropping practices, reducing fallow and
cultivation, irrigation with freshwater, planting salt tolerant species, and
so on.
Salt tolerant : Species able to withstand at high levels of salinity.
Halophytes : Plants which live in salt-affected soils (for example, Saltbush).