To make and use nitrogenous fertilizer on a farm, nitrogen dioxide is prepared in a continuous process from air or from ammonia in a reactor, with the ammonia either being transported to the farm or being prepared on the farm in a continuous process from water and air. The nitrogen dioxide is mixed with a continuous flow of water to form a dilute solution of nitric acid, which may be applied to the field through the irrigation system as top dressing or mixed within the irrigation system with ammonia or other cations to form ammonium nitrate or other desired nitrogen solutions for application to the fields in a continuous process or concentrated without requiring storage of large amounts of gas or creating heat exchange problems in the manufacturing process. In the embodiment which burns ammonia, the nitrogen oxides are fixed on an 8 percent nickel stainless steel mesh in a column 10 feet high and one foot in diameter and oxidized while fixed to nitrogen dioxide. The nitrogen dioxide is dissolved in water flowing through the mesh.