What does the term "Cation Exchange Capacity" refer to?

Cation Exchange Capacity (CEC) refers specifically to the soil's ability to hold and exchange positively charged ions, known as cations. This property is crucial in determining how well soil can retain essential nutrients needed for plant growth, such as calcium, magnesium, potassium, and sodium.

Soils with high CEC can hold more cations, making them more fertile, as they are better able to supply these nutrients to plants. The exchange process occurs when roots release hydrogen ions (H+) into the soil, displacing cations from the soil particles. The released cations then become available for plant uptake. Understanding CEC is vital in soil management and fertility programs, as it influences nutrient availability, soil pH, and overall soil health.

The other options focus on different soil properties: water retention, soil texture and structure, or general nutrient content, none of which specifically address the exchange and holding of cations as CEC does.