soil with relatively low levels of soluble salts and a concentration of sodium high enough to adversely affect soil structure (symptoms include waterlogging. erosion. soil surface crusting. and poor plant growth). Soils > 12 SAR (see sodium absorption ratio).
Sodic soils are characterized by a disproportionately high concentration of sodium (Na) in their cation exchange complex. They are usually defined as containing an exchangeable sodium percentage greater than 15%. These soils tend to occur within arid to semiarid regions and are innately unstable, exhibiting poor physical and chemical properties, which impede water infiltration, water availability and ultimately plant growth.
Sodic soils that are particularly difficult to manage include:
- Saline sodic soils, soils with excess salts where sodium chloride (NaCl) predominates.
- Alkaline soils, soils with a high pH (>8.5) due to the presence of high concentrations of sodium carbonate (Na2CO3).
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