Amber Anderson

Learning Objectives
  • Given an electrical conductivity or exchangeable sodium value, indicate anticipated plant growth impacts
  • Match impacts of saline or sodic conditions on soil properties and plant growth
  • Understand management practices for sodic, saline, and saline-sodic soil
  • Predict management decisions’ impact on soil chemical properties
Keywords: Salinity, saline, sodic, saline-sodic

Salts in the soil

A soil face with the top of the profile degraded deeper due to sodium accumulation.
Degraded structure at the top of the profile here due to sodium accumulation. Photo Credit: Amber Anderson. Click to enlarge

Soluble salts have a harmful effect on the soil and over plant growth. Salinity exists when there is an excessive content of soluble salts, which has a significant effect on soil properties and plant growth. It can be caused by different reasons:

  • Primary salinity: caused by natural conditions, such as weathering of parent materials with high content of soluble salts or at places where evapotranspiration exceeds precipitation rates.
  • Secondary salinity: as a result of human activities, such as poor irrigation practices and excessive use of fertilizers.

It is important to understand that salinity includes a diversity of soluble salts, some of the most common ions are Ca, Mg, Cl, SO4, HCO3, and Na. However, excessive content of Na is problematic, causing sodic soil conditions with negative effects on soil aggregation. Salinity is measured by Electrical Conductivity, and Sodium through the Sodium Absorption Ratio (SAR) or the Exchangeable Sodium Percentage (ESP), which compares the sodium content to total soluble salts.


Plants in the upper right corner. Exposed soil covered in straw with a blue strip on material in the lower portion of the photo. Exposed area of dark brown soil showing white areas is salt accumulation.
Salts accumulating on the soil surface in a hoop house. Photo Credit: Amber Anderson.


  • Normal soil: pH < 8.5, EC < 4 mmhos/cm, ESP < 15 %, SAR < 13
  • Saline soil: pH <8.5, EC > 4 mmhos/cm, ESP < 15 %, SAR < 13
  • Sodic soil: pH > 8.5, EC < mmhos/cm, ESP > 15%, SAR > 13
  • Saline-Sodic: pH < 8.5, EC < mmhos/cm, ESP >15%, SAR > 13
Soil profile in a grassy area with an indent around 1/4 of the way down.
Photo Credit: Amber Anderson.

Problems with salts in soil

  • Can interfere with water and nutrients uptake
  • Poor infiltration/permeability, and aeration
  • Sodium degrades structure and aggregation
  • Sodium also increases pH and affects nutrient availability

Management of salts in the soil

While saline soils can be leached to remove the salts, that may be challenging due to lack of either quality or quantity of water availability. Sodic soils are more problematic, as gypsum should be applied first, and then leached, but soil properties may be degraded to make water moving through the soil more challenging. In some cases, planting more resistant species is a more viable option.

Quick overview of testing for salts in soil

Beyond looking for salt rinds on top of the soil, one can also use a fairly simple procedure in a soil lab to find out the salinity of the soil. Below is a summary of how soils are tested for salts using electrical conductivity. A Thermo Scientific Orion4Star pH and conductivity bench top meter was used for this example.

Soil and water in a small capped plastic tube. The tube in in a 50ml glass beaker located on a black surface.
Photo Credit: Lydia Brown.
  1. Combine soil sample with deIonized water to create a saturated soil in a 1:1 ratio. Allow the soil to settle or centrifuge for 5-10 minutes.
Water from previous soil sample tube after settling located in a small graduated cylinder on a black surface.
Photo Credit: Lydia Brown.

2. Separate the settled solid soil from the water and remove water from sample tube.

A Thermo Scientific Orion4Star pH and conductivity bench top meter probe placed in the graduated cylinder next to the original sample in 50 mL glass beaker on a black surface.
Photo Credit: Lydia Brown.

3. Set up the meter to read electrical conductivity (dS/m or mmhos/cm). Place the meter in the water sample.

A Thermo Scientific Orion4Star pH and conductivity bench top meter with probe inside the graduated cyclinder to the left of the original sample tube in beaker. An open MacBook with a spreadsheet is to the right of the original sample tube and beaker.
Photo Credit: Lydia Brown.

4. Calculate Sodium Absorption Ratio and Exchangeable Sodium Percentage.

  • Sodium Absorption Ratio (meq/L) = Na+ / ((Ca+2 + Mg+2)/2)
  •  Exchangeable Sodium Percentage (%) = (Na+/ CEC) * 100


Key Takeaways
  • Different kinds of salts in the soil can limit water uptake and destroy soil structure and aggregation.
  • Above 4 mmohs/cm is a saline soil.
  • Exchangeable sodium greater than 15% or Sodium Absorption Ratio (SAR) above 13 is a sodic soil.


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Introduction to Soil Science Copyright © 2023 by Amber Anderson is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.