Which of the following is NOT a nitrogen-containing compound used in fertilizers?

Calcium carbonate is not a nitrogen-containing compound used in fertilizers. It is composed primarily of calcium, carbon, and oxygen and serves different purposes in agriculture, such as soil amendment and pH regulation, rather than providing nitrogen, which is crucial for plant growth and development.

On the other hand, ammonium sulfate, nitric acid, and potassium nitrate all contain nitrogen, which is an essential nutrient for plants. Ammonium sulfate provides nitrogen in a form that plants can readily absorb, while nitric acid is often involved in the production of nitrogen-based fertilizers. Potassium nitrate not only supplies potassium, which is important for overall plant health, but it also contains nitrogen, making it beneficial for plant growth. Thus, calcium carbonate stands out as the only option that does not contribute nitrogen, confirming it as the correct answer.