Salinity and Sodicity Salt affected soils limit crop productivity and cause water use inefficiency.


Saline soil:
Characterized by an electrical conductivity (EC) above 4 mmho/cm, pH less than 8.5, and exchangeable sodium percentage(ESP) below 15%.
Sodic Soil:
Characterized by an EC less than 4 mmho/cm, pH greater than 8.5, and ESP above 15%.
Saline-Sodic Soils:
Characterized by an EC above 4 mmho/cm, pH less than 8.5, and ESP above 15%.

* Source for definitions and salt affected soil info: Tisdale, et al.Soil Fertility and Fertilizers: An Introduction to Nutrient Mangagement. 8th Edition.

Salt accumulation is most common type of soil chemical degradation affecting agricultural lands. Tri-Tech crop advisors work to limit salinity by choosing low salt fertilizers and recommending irrigation and management practices aimed at preventing salt build up.

Soils become saline or sodic when salts in groundwater or irrigation water accumulate in upper soil layers. Salt affected soils limit plant growth by causing dehydration and nutrient deficiencies. High electrical conductivity in saline soil solution prevents roots from absorbing enough water to support healthy growth. High pH in sodic soils limits micronutrient availability, and high sodium concentration may cause calcium, magnesium, or potassium deficiencies. Salt affected soils also deter healthy plant growth by damaging soil structure. Salts accumulated at the soil surface inhibit water penetration, increasing surface runoff. In sodic soils, large hydrated sodium ions push clay particles apart, dispersing soil aggregates. Without well-formed aggregates or pore spaces, water and nutrients flow unevenly through the soil.

Salt affected soils are common in arid regions, like southern California, where low rainfall, dry air, and warm temperatures favor soil water evaporation. Arid regions with high water tables are especially prone to developing saline and sodic soils since evaporation pulls the water up through the soil, depositing salts along the way. Soils close to the ocean can suffer salinization caused by ocean water intrusion into groundwater or salt deposition by ocean mist. Poor quality irrigation water also increases salinity and sodicity, or worsens the problem in naturally salt affected soils. When growers are obligated to use low quality irrigation water, Tri-Tech Ag advisors recommend adjusting pH with acid amendments and increasing soil organic matter to help mediate salt damage. Growers can also prevent salt accumulation with soil appropriate leaching and by using products with low salt indices.

Excess salt in this soil has precipitated at the surface forming white crystals. Leaching the soil with good quality water, using low salt fertilizer, adding gypsum, and applying organic matter help restore soil quality and improve crop production.