The amount of positively charged cations soil can hold. Basic cations, or any element with a positive charge, include calcium, magnesium, potassium, and sodium. Acidic cations include hydrogen and aluminum. The CEC of a soil is determined by the amount of cations, clay and humus present in the soil; the higher the number, the more cations a soil can hold. If a soil has a higher CEC, then it has a greater availability of nutrients for plant life, and a bigger capacity to hold nutrients that plant life or grass may need later on. Understanding the Cation Exchange Capacity of your soil can be essential in the overall care for your lawn.