Which of the following components primarily contributes to CEC?

The correct response highlights the significant role of organic matter in contributing to cation exchange capacity (CEC). CEC is a critical property of soil, reflecting its ability to hold and exchange positively charged ions or cations, such as calcium, magnesium, potassium, and sodium.

Organic matter, which includes decomposed plant and animal residues, enhances the soil's ability to retain these nutrients. It is negatively charged, attracting and holding onto cations due to electrostatic forces. This makes organic matter a vital component in enriching soil fertility, improving nutrient availability for plants.

In contrast, nitrogen content, while essential for plant growth, does not directly influence CEC since it primarily exists as a gaseous form in the atmosphere or as highly mobile ions in the soil. Water content, although crucial for soil health and nutrient transport, does not contribute to CEC in itself; rather, it assists in the movement and exchange of ions. Finally, sand content, characterized by larger particle sizes, tends to have lower CEC than finer particles like clay and silt because it has less surface area and fewer charged sites available for ion exchange. Thus, the prominent role of organic matter stands out as the primary contributor to CEC in soils.