Although there are often small traces of salt in soil, an excess amount of salt creates a condition called saline soil. Saline soil holds enough salts to inhibit plant growth, notes New Mexico State University. A soil with a white crust at the surface may have too much soil salinity. Several types of saline soil exist.
Saline soils contain enough salt to injure plants and inhibit plant growth. These soils have a light brown or white crust on the top surface. Electricity is the method of determining how much salt is in soil; the electrical current reading (EC) for saline soils is more than 4 mmho/cm (millimhos per centimeter). Saline soils usually contain table salt, gypsum, magnesium sulfate, potasium chloride and sodium sulfate. The pH of saline soil is usually below 8.5.
Saline-sodic soils are soils with an electrical conductivity reading (EC) that is less than 4. Saline-sodic soils also have a pH, a reading of soil acidity, of less than 8.5. More sodium is present in saline-sodic soils than in saline soils. Water moves through saline-sodic soils much like it does in saline.
The sodic soil condition occurs when the amount of soluble salt in the soil is low, but exchangeable sodium, or sodium that cannot be leached from the soil, remains. A high sodium concentration in sodic soils prevents the development of roots. Sodic soils also have a high pH, between 8.5 and 12, reducing the soil's ability to grow plant life. Sodic soils made of clay become compacted, reducing rain, air and nutrients from penetrating the soil. The soil becomes very sticky when it is wet, and becomes hard and crusty when dried. Sodic conditions rarely occur in sandy soils, since these soils lack any clay content.