FFA Floriculture Practice Test

Which nutrient is retained more effectively by a root medium with high cation exchange capacity (CEC)?

1. Calcium

2. Phosphorus

3. Potassium

4. Nitrogen

The correct answer is: Potassium

The correct answer is potassium. Cation exchange capacity (CEC) refers to the ability of a soil or growing medium to retain and exchange positively charged ions, known as cations, which include key plant nutrients such as potassium, calcium, and magnesium. A medium with high CEC has a greater capacity to hold cations and thus can provide a more stable supply of nutrients to plants. Potassium is a vital nutrient for plant health as it plays critical roles in several physiological processes, including water regulation, enzyme activation, and photosynthesis. When a root medium has high CEC, it effectively holds onto potassium ions, thereby ensuring that plants have consistent access to this nutrient. While calcium, phosphorus, and nitrogen are also essential nutrients, their behaviors in the soil or growing medium can differ. For example, phosphorus tends to bind tightly to soil particles and may not be as effectively retained in a medium focused on cation exchange; it is often more susceptible to being rendered unavailable to plants. Nitrogen exists in both cationic and anionic forms, but its volatile nature means that it can be lost to the atmosphere or leached from the soil, making it less reliable than potassium in a high CEC context. In summary, potassium benefits significantly