Abstract: To make non-pressure nitrogenous fertilizer solutions, nitrogen oxides are prepared in a continuous process by burning ammonia in contact with a cobalt oxide catalyst started by an electric arc without preheating the gases. This burning forms nitrogen oxides which are reacted under negative pressure in a two-stage system. Nitric acid is formed in the first stage from a portion of the oxides by oxidizing them to nitrogen dioxide and reacting the nitrogen dioxide with water. In the second stage, the remaining nitrogen oxides are reacted at a pH between 8.0 and 8.4 in a gas-liquid contacting apparatus with an ammonium hydroxide reaction liquid, formed by mixing ammonia and water. The ammonium nitrite solution formed in the second stage is mixed with the nitric acid at a pH below 0.2, resulting in a solution of acidic ammonium nitrate to be flowed to the fields with irrigation water.