Anhydrous ammonia, which contains 82 percent nitrogen, is the most concentrated nitrogen fertilizer, as well as the “basic” nitrogen product that manufacturers upgrade into other nitrogen fertilizers such as urea and UAN solution.

Because of its high nitrogen content, it is often the most cost-effective nitrogen fertilizer. A gas under ambient conditions but a liquid when refrigerated and pressurized, ammonia requires special equipment and technology to transport, store, and apply.