Which of the following minerals are cations largely retained on the cation exchange capacity of soil?

The minerals that are cations largely retained on the cation exchange capacity of soil include calcium, magnesium, and potassium. These cations are essential macronutrients for plant growth and play significant roles in various physiological processes.

Calcium contributes to cell wall structure and stability, is involved in root development, and enhances nutrient uptake. Magnesium is a vital component of chlorophyll, facilitating photosynthesis, as well as playing roles in enzyme activation. Potassium is critical for several plant functions, including water regulation, enzyme activation, and photosynthesis.

These cations are positively charged and can bond with negatively charged soil particles, allowing the soil to hold onto them effectively. This retention ensures that plants have access to these essential nutrients over time, which is important for plant health and growth.

In contrast, the other options include minerals that either do not play significant roles in cation exchange capacity (like phosphorus, which is primarily an anion in soil and essential mainly for energy transfer; or trace elements that are needed in much smaller quantities) or are less central to the cation exchange process. Thus, the correct answer aligns with the primary role of calcium, magnesium, and potassium in soil cation exchange capacity.