Several different terms are used to describe problem soils in arid regions. This small glossary is an summary of these terms and an aid in sorting out the differences between the different soils.
Alkaline soil is any soil with a pH of greater than 7.0. If it is too high, sulfur or a sulfur-containing chemical is used to lower it.
Alkali is a synonym for sodic soil.
Saline soil contains enough salt to adversely affect plant growth. The salts are usually salts of calcium, potassium, or magnesium, but may be fertilizer salts or salts of other elements. Salts are removed from soil by leaching (flushing) with water. To do this, large amounts of non-saline water are required, and drainage must be adequate to carry the leachate away.
Sodic soil contains enough free sodium to adversely affect plant growth. Sodic soil is reclaimed by adding gypsum or another calcium source, then leaching.
Saline-sodic soil has characteristics of both saline and sodic soils. Saline-sodic soil is saline with a large amount of sodium included in the mix of salts. In this case, the soil shows saline, rather than sodic, symptoms, as the other salts mask the effects of the sodium. If it is leached to treat the salinity however, the calcium, potassium, and magnesium are leached out, leaving the sodium. The soil then displays sodic symptoms, and must be treated as a sodic soil, with gypsum and leaching.