I have spent many hours trying to explain to individuals what this CEC value means. I am sure there are many more individuals who may be too embarrassed to ask. Let's start with the basics. Some of these positively charged elements are potassium, calcium, magnesium, zinc, iron, manganese, copper and ammonium. These elements are called cations.
Soil particles themselves generally have a negative charge inside and on their edges.
Because the soil particles have a negative charge and the cations have a positive charge they are attached together just like a magnet would attract a metal. Since cations are held to the soil by their positive charge, they cannot be leached downward in the soil when water moves through the soil profile. Soils with a high CEC tend to be more fertile and are capable of providing more nutrients to crops. The CEC of the soil will influence the ability of the soil to hold and interact with pesticides too. Pesticides that have a positive charge will be held more tightly to the soil when the CEC of the soil is high.