What does CEC stand for and what does it indicate about soil?

• A. Cation exchange capacity; the soil's ability to hold and exchange positively charged nutrients.
• B. Calcium exchange coefficient; the soil's calcium content.
• C. Chromium extraction capacity; soil pollutant binding.
• D. Clay expansion coefficient; soil texture.

Answer: (A)

Cation Exchange Capacity. This indicates how many positively charged nutrient ions the soil can hold onto and swap with plant roots. Clay minerals and organic matter carry negative charges, which attract cations like potassium, calcium, magnesium, ammonium, and others. A higher CEC means the soil can retain more nutrients and release them gradually, helping fertility and buffering against pH changes; it also reduces nutrient leaching in lighter soils. A low CEC soil holds fewer nutrients, often requiring more frequent fertilization or organic matter additions to boost nutrient-holding capacity. CEC is typically measured as cmolc/kg of soil. Soils with more clay and organic matter tend to have higher CEC, while sandy soils have lower CEC. The other interpretations miss the idea of nutrient holding and exchange.