The World's Greatest Fix: A History of Nitrogen in Agriculture

  • G. J. Leigh
Oxford University Press: 2004. 254 pp. £20, $29.95 0195165829 | ISBN: 0-195-16582-9
Credit: ILLUSTRATIONS BY CHRISTIAN DARKIN

The discovery by Fritz Haber of a method for fixing ammonia from its elements led to the development of the modern nitrogen-fertilizer industry. The growing applications of nitrogen compounds in agriculture have had enormous demographic, economic and environmental consequences. Most histories of nitrogen fixation focus on this part of the story, but in The World's Greatest Fix, G. J. Leigh provides a more evenly distributed account. Nearly two-thirds of Leigh's text is devoted to general considerations of nitrogen's chemistry and agronomy, and of technical developments before Haber's discovery.

The book begins with a brief introduction to nitrogen fixation and its importance for agriculture, before tracing the development of agronomic practices in pre-Colombian America (by the Aztecs and Mayas), dynastic China and the Roman Empire, with particular attention to classic agricultural accounts (and the value of manure) by Cato the Censor, Columella, Pliny the Elder and Varro. Next, the story advances to the modern era, focusing on English farming from Roman times to the beginning of scientific agriculture in the seventeenth century, before moving on to the trade in guano (bird droppings are a rich source of nitrogen) and Chilean nitrates (originally Bolivian and Peruvian) — England was the leading importer of these sources of nitrogen. Leigh then takes us into the laboratory, dealing with the alchemy of nitre and the early chemistry of nitrogen (from Paracelsus to Lavoisier and Chaptal), the birth of agricultural chemistry (thanks to Davy, von Liebig and Boussingault) and the discovery (by Hellriegel and Wilfarth) that microorganisms and some plants can fix their own nitrogen.

Leigh then describes the evolution of the first commercial methods invented to fix nitrogen. The Norwegian arc process, which combines N2 and O2 in an electric arc furnace and uses the resulting nitric oxide to produce HNO3, was made possible by inexpensive hydroelectricity. The synthesis of cyanamide, by reacting CaC2 with N2, also fixed nitrogen but was energy-intensive. Next come Haber's experiments, beginning in 1903, and the quest, led by Carl Bosch, to commercialize them, beginning at the BASF plant in Ludwigshafen, Germany, in 1909. Here I found the only factual errors worth noting: the German chemist who formulated the effective catalysts needed to run the ammonia synthesis was Alwin (not Alois) Mittasch. This work also led to the synthesis of methyl alcohol and the hydrogenation of coal. And Mittasch did not collaborate with Haber in 1903 (at the time he was Ostwald's assistant in Leipzig); he joined BASF in 1904, working under Bosch.

The penultimate chapter explores the continuing mystery of biological fixation, the author's main area of research interest — he spent most of his professional life at the Unit of Nitrogen Fixation, which was set up in the mid-1960s at the University of Sussex. He describes the discovery of nitrogenases — the enzymes that fix nitrogen in both free-living and symbiotic bacteria — and their modes of action; he discusses the structures made up of iron, molybdenum and sulphur that are at the heart of these remarkable molecules; and he reviews the unsolved puzzles regarding their active sites.

In closing, Leigh reviews the scale and effects of nitrogen-fertilizer use, focusing on aquatic eutrophication — in which excessive nitrogen promotes algal growth and the subsequent depletion of oxygen — and nitrates and human health. The health effects of nitrates are frequently exaggerated, but eutrophication, which Leigh treats rather lightly, still does not get enough attention, given its severity and increasing occurrence. There is also now considerable eutrophication of terrestrial ecosystems.

I always like unusual tit-bits, asides and images, and Leigh's book has its share of them. Among my favourites is a reference to Humphrey Davy's discussion of various fertilizers, including pilchards in Cornwall. There is also a photograph of Tyntesfield, an impressive Victorian Gothic Revival mansion built near Bristol between 1863 and 1866, financed largely with money from the guano trade. And there is a description of a frustrated British inspection of the world's first ammonia plant in Oppau, Germany, in 1919 with the intention of reverse-engineering it in Britain. Leigh conveys a great deal of information in 220 pages of text, and does so in an easy-to-read, clear and accurate style. This is altogether a fine book.

Those who would like to know more about the key protagonist of the nitrogen story, yet are unable to read German, can finally get an (abridged) English translation of Dietrich Stoltzenberg's massive 1994 biography Fritz Haber: Chemist, Nobel Laureate, German, Jew (Chemical Heritage Foundation, 2004).