Urea-ammonium nitrate (UAN) is a non-pressure solution of ammonium nitrate, urea, and water. Two grades are most common: 28-0-0 (10.7 pounds/gal) and 32-0-0 (11.1 pounds/gal). The lower analysis material contains more water and can be stored at lower temperatures. Salt crystals will form at about 0^oF for 28 percent solution and at about 32^oF for the 32 percent solution.

Individual solutions can be made from urea or ammonium nitrate; however, higher analysis solutions are possible when urea and ammonium nitrate are combined. Commonly available nitrogen solutions will contain about one-half of the nitrogen from urea and the other half from ammonium nitrate.

UAN solutions have an advantage in terms of handling. They can be pumped, mixed with chemicals and sprayed. They are corrosive and will quickly destroy brass, bronze and zinc fittings. Carbon steel and cast iron are also seriously corroded. UAN doesn’t corrode aluminum alloys, stainless steel, rubber, neoprene, polyethylene, vinyl resins, and glass.

The performance characteristics of urea-ammonium nitrate solutions are the same as for the two main ingredients, urea and ammonium nitrate. The ammonium nitrate portion will perform like ammonium nitrate, and the urea portion like urea.The urease enzyme is present on crop residues and on the soil surface, so the urea portion of this fertilizer is subject to loss unless incorporated by tillage or rain.