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Understanding your Soil

Poor Plant Growth due to High Salt in Soil

Drinking Water Treatment Devices: Distillers

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CSU Extension Factsheets: (also available from the Extension publications website)

 

Poor Plant Growth due to High Salt in Soil

Poor plant growth can sometimes be attributed to high salts in the soil. Salt content can be measured by analyzing the soil for electrical conductivity (EC) and is expressed in units called millimhos/cm (mmhos/cm).

Most plants can usually tolerate EC levels in the soil up to about 2.5 to 3 mmhos/cm, however salt sensitive plants may not grow well if the EC exceeds 2 to 2.5 mmhos/cm. Soils are considered saline if the EC is four or more, sodic (high in sodium) if the pH is greater than or equal to 8.5 and saline-sodic if the pH is greater than or equal to 8.5 and has an EC of 4 or more.

Salts can be naturally occurring in low lying areas where the water table may be close to the surface or they can become high through the addition of too much manure or other high salt containing compost. 

Adding composts or composted manures at a rate of 3 cubic yards per 1000 square feet (about one inch thick on the surface of the soil) and then tilling or rototilling them in about six inches is usually sufficient to prevent high salt concentrations in the soil. Care should also be used when purchasing topsoil to avoid soil that is high in salts.

Some topsoils are mixed with composts or manures which can improve soil structure and nutrient levels, but can also result in high salt concentrations that are detrimental to plants. With some topsoils being delivered at rates of $25 to $40 per cubic yard, it pays to find out if the soil will be acceptable for plant growth by knowing the salt level or EC.