The task of providing adequate nitrogen for crop production in pre-industrial agriculture relied on (1) recycling organic wastes (primarily crop residues and animal wastes), (2) crop rotations that include leguminous plantings, and (3) leguminous cover crops plowed in as green manures.  Nitrogen deficiencies were very common and typically limited crops from reaching their yield potential.  Chilean nitrate and guano became popular as a convenient but expensive way to provide this essential nutrient.  Ammonia synthesis began at a small scale in the early 1900’s using the arc process, the cyanide process, and the cyanamide process.  Discovery of ammonia production techniques by Haber in 1908- where nitrogen and hydrogen are combined with high temperatures and pressures, and the subsequent commercialization of the process by Bosch led to the development of the modern N fertilizer industry.  Military use of nitrates in World War One led to the rapid development of the North American N industry, initially centered in the Muscle Shoals, AL area.  Following World War Two, N fertilizers became widely available at affordable prices.  New manufacturing technology increased efficiency and reduced costs.  The forms of N fertilizer have changed over time to meet the need of growers.  The current high price of natural gas required for synthesis has resulted in closure of some less efficient fertilizer plants and an increase in off-shore imports.