Appendix A: Resource Material

Saline and Alkali Soils

Saline and alkali soils have excessive levels of soluble salts, consisting mainly of sodium, calcium, magnesium, chloride, and sulfate and secondarily of potassium, bicarbonate, carbonate, nitrate, and boron. Soluble salts in the soil water (soil solution) can be high enough to negatively affect plant growth.

Saline and alkali soils are common in arid and semi-arid parts of the world. Low precipitation and low soil permeability in arid ecosystems contribute to the buildup of salts in the soil that would be leached by water down to deeper soil layers below the plant root zone.

Excess levels of salts in the soil root zone limit the ability of plant roots to absorb soil water. Water flows osmotically from low salt concentration to higher salt concentration. Roots uptake water osmotically by having a higher salt concentration than the surrounding soil water pool. Saline and alkali soils reverse the osmotic potential of plant roots and soil water.

One agricultural solution to improve salt effected soils is to “leach” the salts down deep into the soil using a lot of water. By leaching the salts below the root zone, plants can grow normally; but not all salts are equally mobile in water. Table salt is more soluble in water than baking soda because of the difference in polarity, bond types, and compound size.

The Plant Growth and Osmotic Potential project was brought to you by the Great Basin Rangelands Research Unit in Reno, NV.