The cation exchange capacity (CEC) shows how well a soil can hold onto and store cations, so a soil with a high CEC would be able to hold more nutrients. A soil with low CEC for example would not only be missing some important nutrients but would also not be able to hold onto nutrients as well as a soil with a higher CEC. So even adding nutrients to a soil with a low CEC would not be very effective in improving fertility unless soil conditioning was applied that would help improve the CEC as well. Soils with a lot of cations can also hold onto water better since water is a polar molecule and is therefore attracted to the positively charged cations (hydrogen bonding).
Plants that grow in soils with a high CEC value do not have to spend as much energy looking for minerals and water and therefore are able to devote it towards growth. Microorganisms that are essential for good soil health also thrive in these conditions.
However, a soil with a high CEC can also hold more of the acidic hydrogen cations (H+). So when the soil pH of a soil with a high CEC needs to be adjusted it often acts as a buffer and therefore more acid or base is need to change the pH.
Soils have a cation exchange capacity (CEC) rating that indicates its ability to hold and exchange plant nutrient cations. In simpler language, it is a measure of the soil’s ability to hold the fertiliser you apply (instead of it being leached) and transfer it to plants.
In most soils the CEC rating is 12-14 but in sandy soils it can be 1-2.
In peat it is 40-50 because there is a close correlation between the holding ability and how much carbon and humus is in the soil. potassium humate generally have a CEC of 200 and our potassium humate has one of about 250.
Electrically charged sites on humic substances function to dissolve and bind trace minerals. When a complex reaction with metal cations occurs on the humic substance surface it is termed chelation. Two negatively charged sites on the humic substance attract metal cations with two negative charges. As a result the cation binds itself to more than one charged anionic site. By forming organo metal claws these organic acids bring about the dissolution of primary and secondary minerals within the soil. These minerals then become available for uptake by plant roots. The greater the affinity of the metal cation for humic acid (HA) or fulvic acid (FA), the easier the dissolution of the cation from various mineral surfaces. Both the acidic effect and the chelation effects appear to be involved in dissolution of minerals and
binding processes. Evidence for the dissolution of minerals can be supported by x ray diffraction and infrared analysis.
Chelation of plant nutrients such as iron (Fe), copper (Cu), zinc (Zn), magnesium (Mg), manganese (Mn), and calcium (Ca) reduces their toxicity as cations, prevents their leaching, and increases their uptake rate by plant roots.