Soil Salinity and Sodicity
Soil salinization occurs as salts (e.g. calcium, potassium, magnesium) accumulate in the soil, particularly in irrigated regions with low rainfall and high evapotranspiration. Similarly, soil sodicity refers to high sodium (Na) levels in soil. These conditions can cause plant moisture stress as roots have trouble taking up water from the soil. High sodium levels cause soil particles to disperse, clogging soil pores and exacerbating issues with erosion.
There are three types of salt-affected soils:
- Saline soils contain high concentrations of soluble salts. Soluble salts present in the root zone can make it difficult for plants to extract water from the soil.
- Sodic soils have too much sodium.
- Saline-sodic soils have too much sodium and other soluble salts.
Soils with excessive salts can create soil sealing which restricts water infiltration.
Photo credit: Deirdre Griffin LaHue
Management practices differ for saline, sodic and saline-sodic soils:
- Saline soils are reclaimed by leaching salts below the root zone with the application of low-salt irrigation water. Plants are most susceptible to soil salinity at germination. In some cases, moving salt away from the germinating seed is all that is necessary.
- Sodic soils require the addition of soluble calcium, followed by leaching of sodium. Calcium promotes soil aggregation. Gypsum is the most common material used to supply calcium for sodic soil reclamation. Elemental S is useful for sodic soil reclamation only when the soil contains free lime.
- Saline-sodic soils must be treated for sodicity first. These soils first require calcium additions to correct sodium, followed by leaching to remove salts.
When developing a plan for salt management, keep in mind these concepts:
- Irrigation water can create or worsen salt-affected soil conditions, making irrigation water management important. Test your irrigation water for salt before using.
- Some crops are more sensitive to salts than others, and plant sensitivity varies depending on crop growth stage and weather.
- High concentrations of chloride and boron can reduce crop yield independent of saline or sodic soil conditions.
- Reclamation of salt-affected soils requires adequate drainage. If necessary, improve drainage before attempting reclamation.
