Chapter 15

Saline, Sodic, and Saline-Sodic Soils

(book excerpts)

Salt-affected soils can significantly reduce the value and productivity of affected land. Salt-affected soils may contain excess soluble salts (saline soils), excess exchangeable sodium (sodic soils), or both (saline-sodic soils). Salt affected soils commonly contain a mixture of cations of sodium, calcium, magnesium and potassium and anions of chloride, sulfate, bicarbonate, carbonate and sometimes borate and nitrate. The major factor responsible for the formation of salt-affected soils is the redistribution of salts within the soil, with water as the primary carrier. Where rainfall is high, most salts are leached out of the soil. In arid regions, the salt levels accumulated in soils can be very high because of limited or reduced leaching. However, not all soils in arid regions are salt-affected because the soil parent materials are not contributing sources of salts. Indirect sources of salts include irrigation water coming from saline sources or saline water from groundwater wells. Saline soils are often referred to as “white alkali” because of the white salt crust that forms on the soil surface. Saline soils can affect soil physical properties by causing fine particles to bind together into aggregates. This process is known as flocculation and is beneficial in terms of soil aeration, root penetration, and root growth. Although increasing soil solution salinity has a positive effect on soil aggregation and stabilization, at high levels salinity can have negative and potentially lethal effects on plants both physically (osmotic effect) and chemically (nutrient and/or toxicity effect). Sodic soils are often referred to as “black alkali” or “slick spots” because of the dissolved organic matter in the soil solution. The exchangeable sodium causes soil particles to disperse, resulting in decreased pore space within the soil and increased soil crusting. The loss of permeability due to less pore space can severely restrict water movement into the root zone resulting in plant stress from lack of water. Crusting can severely affect seedling emergence.

Click on the following topics for more information on saline, sodic, and saline-sodic soils.

Topics Within This Chapter:

  • Classification of Saline, Sodic, and Saline-Sodic Soils
  • Measuring Salinity and Sodicity
  • Salinity
  • Sodicity
  • Sources of Salinity and Sodicity
  • Saline Soils
  • Salinity Effects on Soil Physical Properties
  • Salinity Effects on Plant Growth
  • Management of Saline Soils
  • Leaching
  • Leaching Methods
  • Timing of Leaching Events
  • Determining Leaching Requirement
  • Estimating Applied Water for a Desired Leaching Requirement
  • Drainage
  • Irrigation Strategies
  • Irrigation Timing
  • Furrow Bed Systems
  • Frequent Irrigations
  • Residue Management
  • Growing Salt-Tolerant Crops
  • Sodic Soils
  • Sodium Effects on Soil Physical Properties
  • Sodium Effects on Plant Growth
  • Management of Sodic Soils
  • Reclamation of Sodic Soils with Chemical Amendments
  • Types of Amendments
  • Quantity of Amendment
  • Additions of Organic Matter
  • Acidification of Irrigation Water
  • Saline–Sodic Soils
  • Saline-Sodic Soil Management