In soil science, cation exchange capacity (CEC) is the capacity of a soil for ion exchange of positively charged ions between the soil and the soil solution. (A positively-charged ion, which has fewer electrons than protons, is known as a cation.) Cation exchange capacity is used as a measure of fertility, nutrient retention capacity, and the capacity to protect groundwater from cation contamination. Soil science deals with soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils per se; and these properties in relation to the use and management of soils. ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For the American hard rock band, see SOiL. For the System of a Down song, see Soil (song). ... Ion exchange is defined as an exchange of ions between two electrolytes. ... This box:      Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... This article is about the electrically charged particle. ... Soil fertility is the characteristic of soil that supports abundant plant life. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. ...

The quantity of positively charged ions (cations) that a clay mineral or similar material can accommodate on its negatively charged surface, expressed as milli-ion equivalent per 100 g, or more commonly as milliequivalent (meq) per 100 g. Clays are aluminosilicates in which some of the aluminium and silicon ions have been replaced by elements with different valence, or charge. For example, aluminium (Al³⁺) may be replaced by iron (Fe²⁺) or magnesium (Mg²⁺), leading to a net negative charge. This charge attracts cations when the clay is immersed in an electrolyte such as salty water and causes an electrical double layer. The cation-exchange capacity is often expressed in terms of its contribution per unit pore volume, Qv. The equivalent (Eq or eq) is a reasonably common measurement unit used in chemistry and the biological sciences. ... Aluminum redirects here. ... General Name, symbol, number iron, Fe, 26 Chemical series transition metals Group, period, block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ...

Base saturation

Closely related to cation exchange capacity is the base saturation, which is the fraction of exchangeable cations that are base cations (Ca, Mg, K and Na). The higher the amount of exchangeable base cations, the more acidity can be neutralised in the short time perspective. Thus, a site with high cation exchange capacity takes longer time to acidify (as well as to recover from an acidified status) than a site with a low cation exchange capacity (assuming similar base saturations). The long term resistance to acidification, however, is determined by the weathering rate. Acids and bases: Acid-base reaction theories pH Self-ionization of water Buffer solutions Systematic naming Electrochemistry Acid-base extraction Acids: Strong acids Weak acids Mineral acids Organic acids Bases: Strong bases Weak bases Organic bases edit An acid-base reaction is a chemical reaction between an acid and a... For other uses, see Calcium (disambiguation). ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... General Name, symbol, number potassium, K, 19 Chemical series alkali metals Group, period, block 1, 4, s Appearance silvery white Standard atomic weight 39. ... For sodium in the diet, see Salt. ... For other uses, see Acid (disambiguation). ... Neutralization is a chemical reaction, also called a water forming reaction, in which an acid and a base or alkali (soluble base) react and produce a salt and water. ...

Laboratory determination

There are two standardised International Soil Reference and Information Centre methods for determining CEC: The International Soil Reference and Information Centre is an independent foundation funded by the Netherlands Government. ...

• extraction with ammonium acetate; and
• the silver-thiourea method (one-step centrifugal extraction).

There exists slightly conflicting ideas on which mechanisms to include in the term, "cation exchange", in soil chemistry. From a theoretical point of view, one should distinguish cation exchange from ligand exchange, and exchange of diffuse layer adsorbed cations. On the other hand, from a practical point of view, e.g. in forest and agricultural management, what is important is the soils' ability to replace one cation with another rather than the exact mechanism by which this replacement occurs. What is included in the term, "cation exchange", in soil science thus varies with the scientific context. Ammonium acetate is the salt of ammonia and acetic acid. ... Centrifugal force (from Latin centrum centre and fugere to flee) is a term which may refer to two different forces which are related to rotation. ... Soil science deals with soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils per se; and these properties in relation to the use and management of soils. ... In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a... Adsorption is a process that occurs when a gas or liquid solute accumulates on the surface of a solid or, more rarely, a liquid (adsorbent), forming a molecular or atomic film (the adsorbate). ... This article is about a community of trees. ... For other uses, see Management (disambiguation). ... Soil science deals with soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils per se; and these properties in relation to the use and management of soils. ...

References

• ISRIC (International Soil and Reference Information Centre)
• Robert Lippert, Clemson University Extension Service
• Microsoil.com Cation Exchange Capacity
• David B. Mengel, Department of Agronomy, Purdue University