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The challenge and the solution were described in memorable terms in September 1898 by William Crookes, a chemist and a physicist, in his presidential address on wheat delivered at the British Association’s annual meeting in Bristol. The most quoted sentence from his presentation was that “all civilised nations stand in deadly peril of not having enough to eat,” and he estimated that the rising demand would bring a global wheat supply shortfall as soon as 1930. But he also identified the most effective solution and its most important component: increased crop fertilization and higher applications of nitrogen, the macronutrient that most often limits wheat (and indeed all cereal) yields. Crookes correctly observed that neither the animal manures nor the planting of green manures (alfalfa, clover) could meet future needs, and that the supply of the era’s only important inorganic fertilizer, Chilean nitrates mined in the desert of Atacama, was obviously limited. What was needed was to tap the unlimited supply of atmospheric nitrogen, to change the inert molecule (N2) that forms nearly 80 percent of air’s mass into a reactive compound (preferably ammonia, NH3) that could be assimilated by crops and supply the macronutrient guaranteeing higher yields.
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