Nitrogen as a Fertilizer
Ancient cultures grew up around the river deltas like the Nile, Euphrates and Tigris and Indus. Outside these naturally fertilized areas, large and sustainable societies were hard to establish. The slash-and-burn technique was utilized since prehistoric times. In the pre-industrial times farmers were limited to using manure and organic waste as fertilizers.
The understanding of the role of nutrients in the growth mechanism of crops was explained and fully understood in 1840 by German chemist Justus von Liebig. The scientific proof of the mechanism was done with isotope tracing of the molecules in the 1965. Plants can only take up fully mineralized nutrients like NH3, NO3, PO4, SO4, etc.
The natural sources for nitrogen were mainly Chilean nitrates and the rapidly depleting deposits of guano. Until the early 20thcentury, the industrial production of nitrogen fertilizer came mainly from ammonia taken out as a by-product from coke production and made into ammonium sulfate. In 1898 Sir William Crook predicted also an exhaustion of the Chilean nitrates and the coming of a severe starvation around 1931.
To solve the nitrogen deficiency therefore became a challenge for the chemical industry, which was developing fast at this time. The solution several scientists in leading industrial countries were looking for was to take NO gas out of thin air by means of an electric arc. The electric arc was known to be able to “burn” the air and make NO gas, which could be further oxidized to NO2.