Which of the following fertilizers is known for being a fast-acting nitrogen source?

Ammonium nitrate is recognized as a fast-acting nitrogen source due to its high solubility in water, which allows for quick uptake by plants. When applied to the soil, it dissolves rapidly and releases nitrogen in the form of ammonium and nitrate ions. This dual availability of nitrogen ensures that plants can utilize it immediately, promoting rapid growth and development.

In contrast, other fertilizers like ammonium phosphate provide phosphorus alongside nitrogen but are not categorized as primarily fast-acting nitrogen sources. Natural organics tend to release nutrients more slowly, as they depend on microbial activity to break down organic matter, which takes time. Ureaform materials, although they contain nitrogen, require microbial breakdown to convert to plant-available forms, making them less immediate in terms of nitrogen availability compared to ammonium nitrate.