Soil Salinity

Salinity is assessed by measuring the electrical conductivity (EC) of a soil-water extract, since dissolved salts conduct electricity in proportion to their concentration. Higher EC values indicate greater accumulation of soluble salts in the root zone.

Saline soil

Elevated soluble salt concentration in the soil solution, measured as electrical conductivity.

Sodic soil

Elevated exchangeable sodium relative to other cations, which disperses clay and degrades structure, independent of total salt level.

Saline-sodic soil

A soil exhibiting both elevated total salts and elevated exchangeable sodium.

Dissolved salts raise the osmotic pressure of the soil solution, making it harder for plant roots to draw in water even when the soil appears moist — an effect sometimes called physiological drought. Some ions, notably chloride and sodium, can also accumulate in plant tissue to toxic concentrations. Sodic soils additionally lose structural stability, restricting drainage, aeration, and root growth.

Laboratories report soil salinity as EC of a saturated-paste extract (or a standardized dilution) and assess sodicity via SAR or exchangeable sodium percentage. Field indicators — visible salt crusts, patchy or stunted crop stands, and slow water infiltration — can suggest a problem but are not a substitute for testing.

Management focuses on preventing further accumulation and, where feasible, leaching accumulated salts below the root zone using good-quality water and adequate drainage. Sodic soils typically require a calcium source, such as gypsum, to displace exchangeable sodium before leaching can restore structure.

• Improve or install drainage so leached salts can move below the root zone
• Use irrigation water quality testing to avoid adding further salt load
• Apply gypsum or other calcium amendments to address sodicity where indicated by testing
• Select relatively salt-tolerant crops for affected areas while remediation is underway

Salinity risk is closely tied to climate and irrigation method. Arid and semi-arid regions with high evaporative demand concentrate salts at the surface, and irrigation methods that wet the whole soil surface can increase this risk compared with methods that apply water more precisely to the root zone.