Defecating animals make crops grow well, probably the first farmers have already seen the effects of nitrogen. The scientific understanding of what happened there came much later. In 1563 Bernard Palissy described that plants use what is in the soil to grow and that manure was good for the soil. He called all nutrients ‘salts’, but his insight gave the starting signal for research into nitrogen.

1772 is credited as the year nitrogen was officially discovered, by Scottish scientist Daniel Rutherford. He put mice in a sealed glass container and then removed all oxygen and carbon dioxide from the container. The mice died. ‘Noxius air’, harmful air, he called the air in which nothing could live and nothing could burn.

The chemical symbol N does not come from noxius but from nitrogenium, the Latin name for the element, which means “producing saltpeter.” The Dutch name nitrogen is derived from the French name: azote, or ‘no life’. A depressing name for an element that is so important to all life.

The atmosphere consists of 78 percent nitrogen. Not as a separate element, but in the form of dinitrogen, N2. With N2 plants and animals can’t do much, they need a reactive form of nitrogen. In 1856 it was discovered that decaying plants release nitrogen, which was the first indication that there is such a thing as a nitrogen cycle. That it is bacteria in the roots that convert nitrogen into a reactive, usable form was only discovered in 1880.

Meanwhile, in the 1930s and 1940s, experiments with soil, crops and manure were in full swing. It was discovered that nitrogen in the soil could be used up and so had to be replenished when farming was practiced. It also became clear that crops grew better on manure with a lot of nitrogen. And: plants were found to be able to absorb nitrogen from various sources, such as rainwater, manure and ammonium sulphate added to the soil.

The world population was growing. It would soon no longer be possible to grow so many crops using only natural nitrogen sources that everyone could eat them. There was also an artificial source: ammonia. But making it was way too expensive.

At the beginning of the twentieth century there was another reason to produce ammonia on a large scale: ammunition. In the run-up to World War I, Fritz Haber and Carl Bosch discovered a cost-effective way to make ammonia. Using a catalyst (iron), they convert nitrogen and hydrogen into ammonia (NH3). Their process is still at the basis of the fertilizer industry, of which ammonia is one of the most important components.

After World War II, fertilizer became commonplace. Ammonia production rose from 5 million tons in 1950 to more than 200 million tons in 2020. People have become better at introducing nitrogen into the environment than nature itself. But too much is never good. Too much nitrogen – and we’re not even talking about nitrogen from exhaust gases here – has disrupted the natural nitrogen cycle. The understanding of nitrogen brought humanity a lot, but now we are left with it.

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