Which one among the following fertilizers is a source of nitrogen? 

CONCEPT:

Nitrogenous Fertilizers

• Nitrogenous fertilizers are compounds that provide nitrogen to plants. Nitrogen is a crucial nutrient for plant growth as it is a major component of chlorophyll, amino acids, and nucleic acids.
• Common nitrogenous fertilizers include substances like urea, ammonium sulfate, and ammonium nitrate.

EXPLANATION:

• Superphosphate is primarily a source of phosphorus (P).
• Potassium sulfate provides potassium (K) and sulfur (S).
• Bone meal is rich in phosphorus (P) and calcium (Ca).
• Urea contains a high percentage of nitrogen (N).
• Therefore, urea is the fertilizer that serves as a source of nitrogen.

Therefore, the correct answer is Urea.