Salt accumulation in soil can reduce crop yields and irrigation effectiveness, and affect soil structure and other soil properties. The predominant salts that accumulate in soils are calcium, magnesium, sodium, potassium, sulfate, chloride, carbonate and bicarbonate. However, any salt that accumulates in excess amounts in the soil can cause plant growth problems.
Management of salt-affected soils is a challenge because salts affect many processes, including crop growth (yield, quality and economic return), soil physical properties (aggregation and water infiltration), and availability and toxicity of nutrients. Soil testing indicates risk of soil and crop damage from salts.
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.
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.
This publication is designed to assist in evaluating the kind and amount of salts present in soils and to select appropriate management practices to maintain soil health and crop productivity.
The “For more information” section provides additional resources on this topic. A companion publication, PNW 597, provides additional details on interpretation of irrigation water analyses.