General view of culture samples used for an experiment to determine if corn growing under sterile conditions can use ammonia nitrogen. This experiment was conducted at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. A notation with the photograph notes that nitrogenous salts were applied at the rate of 100 milligrams nitrogen per bottle. The samples are identified as follows (left to right): No nitrogen; Ammonium sulfate; Sodium nitrate; Ammonium sulfate 50 percent; Sodium nitrate 50 percent; Calcium nitrate; Ammonium phosphate.

The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American University in 1919 under the directorship of Arthur B. Lamb. Initially part of the War Department, the F.N.R.L. was the successor to several wartime initiatives to develop a secure domestic supply of nitrate compounds necessary for the manufacture of explosives during World War I. With a staff of about 110 individuals, including 35 to 50 chemists, the F.N.R.L. focused on the manufacture, production, and development of products of atmospheric nitrogen, including munitions and fertilizers.