Which salt is commonly used to provide nitrogen in fertilizers?

The correct choice, ammonium nitrate, is commonly used in fertilizers because it provides both nitrogen and oxygen to plants. Nitrogen is essential for plant growth as it is a key component of amino acids, proteins, and chlorophyll, which are crucial for photosynthesis.

Ammonium nitrate is particularly effective as a nitrogen source because it is water-soluble, allowing it to be readily absorbed by plant roots. This solubility boosts the immediate availability of nitrogen, promoting healthy growth and development. Furthermore, ammonium nitrate supplies nitrogen in both ammonium and nitrate forms, which can be utilized by plants in different ways depending on their growing conditions.

Other options mentioned do not primarily serve as sources of nitrogen for plants. Potassium sulfate mainly provides potassium and sulfur, which are important for various plant functions but do not supply nitrogen. Calcium phosphate is primarily a source of phosphorus, vital for root development and energy transfer in cells. Magnesium sulfate contributes magnesium, essential for chlorophyll production, but lacks nitrogen. Therefore, ammonium nitrate is uniquely suited for providing the necessary nitrogen in fertilizers.