CEC Explained

CEC (Cation Exchange Capacity)

CEC is a calculated value that is an estimate of the soils ability to attract, retain, and exchange cation elements. In order for a plant to absorb nutrients, the nutrients must be dissolved. When nutrients are dissolved, they are in a form called “ions”. This simply means that they have electrical charges. Larger CEC values indicate that a soil has a greater capacity to hold cations (cation is a positive charged ion). Therefore, it requires higher rates of fertilizer or lime to change a high CEC soil.

When a high CEC soil has good test levels, it offers a large nutrient reserve. However, when it is poor, it can take a large amount of fertilizer or lime to correct that soil test. A high CEC soil requires a higher soil cation level, or soil test, to provide adequate crop nutrition. Low CEC soils hold fewer nutrients, and will likely be subject to leaching of mobile “anion” nutrients.
Base Saturation is a measurement, or estimate of the percent of the soil CEC that is occupied by a particular nutrient (nutrient saturation), or the sum of a group of nutrients (base saturation). This information gives us another tool to use in predicting the soils ability to provide adequate crop nutrients, and indicate needed changes in fertilizer or lime programs.