Interpretation of Mineral Soil Test Results for Salinity

Soil Salinity (or soluble salts) in mmhos/cm (1part soil to 2 parts water method).  The total dissolved solids (ppm or mg/L) can be approximated by multiplying the soluble salts (mmhos/cm) by 1280.

Soil Textural Classification

^{(Values in chart refer to the soluble salts in mmhos/cm)}

Most salt problems develop directly from salts added by irrigation water, therefore, salts must be removed by leaching before they accumulate and become a problem.  Proper irrigation management and adequate drainage are essential to prevent salinity problems. The only way to remove salts from the soil is by leaching them below the rootzone.

With adequate rainfall, leaching may not be required.  However, during drought conditions, leaching by applying excessive irrigation water is necessary to prevent salinity problems.  Where a restrictive soil layer prevents the downward movement of water, lateral tile drains installed directly above the restrictive layer are needed.

To leach salts below the rootzone, “extra” water is needed beyond that required to “wet” the rootzone.  The amount of the “extra” water needed to leach salts increases with turfgrass sensitivity and with the salt content of the water.  The best method to help prevent the buildup of salts in soil is by watering turfgrass as infrequently as possible, but deeply irrigating when water is applied.

Where restrictive layers develop in the rootzone, cultivation or aeration may be required before attempting to leach salts through the soil.  Deep-tine aeration is an effective way to improve water movement through a layer in the top 10 to 12 inches of the rootzone.

When sodium constitutes a significant amount of the salts found in soil or in the irrigation water, additions of gypsum may be necessary.  The calcium in gypsum replaces the sodium on the soil particles and allows water to move the sodium below the rootzone. Soil tests will indicate the need for amendments such as gypsum.