The rising fertilizer use accompanying more people eating more has been called exponential (1) and prompted fears of polluted water and consequent methemoglobinemia (2) and hypoxia (3). It also has raised alarm about greenhouse warming (4) and an altered global N cycle and thus primary production (5) and diversity (1) of vegetation. In this plethora of issues we concentrate on a few, beginning with the fundamental one of how fast N fertilizer use has risen in the world and in an industrial nation, the United States, where early, rapid adoption may foretell the course in the world. We also shall explore how much deposition of N from the atmosphere has increased. After examining the changing ratio of fertilizer N application to its intended incorporation in crop yield, we shall discuss prospects for more or less N fertilizer by 2070 when the earth’s farmers may be feeding 10 billion people and sparing more or less habitat for nature. Because nitrogen (N) comprises fully 16% of protein, neither we, other animals, nor plants grow and survive unless roots extract it from the soil. Medieval wheat crops of only 1,000 kg hectare (ha)−1 extracted 21 kg of N (6). Some N deposited by precipitation or fixed by legumes helped replenish the supply. By rotating their wheat crops onto one of the other, say, 4 ha of the farm or collecting manure from it, medieval farmers could complete the replacement of the N annually removed by 1 ha of wheat. The farm could sustain only a few people because N inevitably escapes from the cycle of deposition, fixation, crops, and animals, and each person requires at least 3 kg of N per year (7). During the 19th century, mining Chilean nitrate and Peruvian guano somewhat relieved this …