What is the starting material for most nitrogen fertilizers?

Ammonia (NH3) is often the starting material for the production of most nitrogen fertilizers due to its high nitrogen content and its chemical properties that facilitate conversion into various forms of nitrogen compounds used in fertilizers.

In the production process, ammonia can be oxidized to form nitric acid, which is a key component in the production of ammonium nitrate and other nitrogenous fertilizers. Ammonia can also be directly utilized to produce urea, another commonly used nitrogen fertilizer. The versatility of ammonia makes it a fundamental building block in nitrogen fertilizer manufacturing.

Other options like ammonium nitrate, nitric oxide, and nitrogen gas represent different forms or processes associated with nitrogen but are not the primary source material for nitrogen fertilizers in a straightforward manner. Ammonium nitrate is a fertilizer made from ammonia, while nitric oxide is an intermediary compound in nitrogen processes, and nitrogen gas is inert and not directly usable by plants without fixing into a bioavailable form. This emphasizes the importance of ammonia as the foundational material for synthesizing a wide range of nitrogen fertilizers.