Published by EH.NET (November 2001)

Vaclav Smil, Enriching the Earth: Fritz Haber, Carl Bosch, and the

Transformation of World Food Production. Cambridge, MA: MIT Press, 2001.

xxii + 338 pp. $34.95 (hardcover), ISBN: 0-262-19449-x.

Reviewed for EH.NET by D. Gale Johnson, Professor of Economics, Emeritus,

University of Chicago.

This is a book about nitrogen, an essential nutrient for all plants. It

begins with the discovery and demonstration of the role of nitrogen in plant

growth. The nitrogen available to plants has several natural sources — the

ammonia present in rain and that deposited by leguminous crops, supplemented

by manure, derived from both animals and humans. The story is told of the

intellectual conflicts between Justus von Liebig, who maintained that all

nitrogen available to plants came from the atmosphere, and researchers at the

famous Rothamsted Experimental Station in England who through experiments with

wheat showed that the nitrogen from the atmosphere was insufficient to have a

significant effect on yields while the application of ammonium sulfate or

manure resulted in significant increases in yields, roughly double those of

fields fertilized only by the nitrogen in rain. Professor Smil of the

Department of Geography of the University of Manitoba develops this and other

stories in an interesting and informative way.

The major story is the development of the process by which nitrogen can be

extracted from the air. In contrast to other sources of nitrogen, such as

guano and South American sodium nitrate, which were exhaustible, there is an

inexhaustible supply of nitrogen in the air. The problem was how to extract

that nitrogen at reasonable cost.

Chapter 4 deals with the work of Fritz Haber who achieved the successful

extraction of ammonia from the air. Chapter 5 discusses the role of Carl Bosch

and the BASF firm in the commercialization of the process. An important reason

for the rapid development of commercialization was the First World War.

Germany was cut off from its supply of nitrates, used in the production of

munitions. BASF stepped in and supplied the material.

In Chapter 8 Smil speculates about the effect that the availability of

synthetic nitrogen has had on the world’s population. He argues that the world

is enormously dependent on nitrogen and that less than half of the current

world population could be fed without the availability of synthetic nitrogen:

” . . . only about half of the population of the late 1990s could be fed at

the generally inadequate per capita level of 1900 diets without nitrogen

fertilizer. And if we were to provide the average 1995 per capita food supply

with the 1900 level of agricultural productivity, we could feed only about 2.4

billion people, or just 40% of today’s total” (p. 160).

Smil notes that during the nineteenth century that the world was able to feed

the unprecedented population increase from 1.0 billion to 1.6 billion by

expanding the cultivated area (p. 39). The expansion occurred primarily in

North America, Australia and Russia and was sufficient to permit an increase

in per capita food supplies. The expansion of area continued in the twentieth

century but concern was expressed at the beginning of the century that

insufficient land was available to meet the needs of the growing population.

William Crookes argued that if the low wheat yields that existed in the 1890s

were to continue (and they did for at least a half century), the increase in

global demand would result in a deficiency of wheat as early as the 1930s.

What Crookes did not foresee, and what Smil does not recognize, was the role

the tractor played in contributing to the food supply, especially in the

industrial nations, after World War I. It was estimated that draft animals

utilized a quarter of all the harvested output of American agriculture in the

1920s (Gray, 1924). In fact, researchers in the United States Department of

Agriculture wrote a long article in the early 1920s in which they indicated

that the United States would have to reduce its consumption of animal products

in order to feed a population of 150 million (Gray, 1924). The United States

reached a population 150 million in 1950 and was somewhat better fed than in

1920. Why were these very competent researchers wrong in their projection?

First, they did not foresee that by the time the population reached 150

million that horses and mules would be largely replaced by the tractor,

releasing up to a quarter of the nation’s crop output. Second, one reason for

their gloom was that grain yields in the United States had increased very

little since the 1860s and they saw no reason to expect significant yield

increases in the future.

Smil makes no mention of the tractor and other forms of mechanical power that

have contributed significantly to the available food supply for humans — true

much more so in the industrial countries than in the developing countries but

clearly significant for the world as a whole.

While there is no doubt that synthetic nitrogen fertilizer has had an enormous

impact on the world’s food supply, Smil largely fails to recognize that this

innovation was a necessary but not sufficient condition for the enormous

increase in food that has occurred over the last half century. The varieties

of grain available prior to the mid-1930s were not responsive to significant

amounts of added nutrients. Yields of corn and wheat in the United States were

essentially the same in the late 1920s as in the late 1860s or even in 1800

(USDA, 1962). The corn yield per acre averaged 25.3 bushels in 1866-70 and

26.5 in 1925-29, while wheat yields were 12.3 and 14.1. Wheat yields in

England were 2.08 metric tons per hectare in 1832-59 and 2.25 tons in 1918-45

(Austin and Arnold, 1989), an increase of less than 10 percent in nearly a


Hybrid corn, which became commercially available in the mid-1930s, was the

first variety of grain that was responsive to significant amounts of nitrogen

and other nutrients. By 1960 corn yields in the United States were double what

they were in the late 1920s and are now five times that level. In the 1960s

new high-yielding varieties of rice and wheat were developed and large yield

increases have been achieved. Smil notes that the use of nitrogen fertilizers

did not increase significantly until the late 1940s when U.S. consumption was

approximately 0.25 million tons; it reached 11 million tons by 1980. It didn’t

increase prior to the 1940s because it was not profitable to use.

It is very surprising that Smil says so little about the complementary

relationships between improved grain varieties and the rapid growth of

nitrogen application. I found only two brief references to hybrid corn (pp.

116 and 150) and one reference to the Green Revolution (p. 139), plus a rather

demeaning footnote.

The footnote (no. 30, p. 296): “The Green Revolution did little for yields of

nonstaple cereals, legumes and oil crops. Its diffusion has been very uneven .

. . and some of its socio-economic and environmental consequences have been

widely criticized in many books published since the 1960s.” There is no

recognition that grain yields in developing countries more than doubled

between 1964-66 and 1994-96 after a long period of stagnation and the daily

per capita supply of calories in the same countries increased by 23 percent

between 1970 and 1996 — a quite remarkable achievement for a flawed


It is rather ironic that a major environmentally adverse effect of modern

grain production is the leaching of nitrogen into rivers, lakes and other

sources of water supplies. Smil recognizes the negative effects of the high

level of use of synthetic nitrogen for the industrial countries (pp. 192-197)

and for rice in the developing countries (p. 219). It is somewhat odd for him

to attribute environmental costs to the Green Revolution without directly

acknowledging the role that his heroes — Haber and Bosch — had in harming

ecosystems throughout the world.

This is a remarkably well-documented book — there are 813 footnotes. It has a

high standard of scholarship. It makes a very strong case for the importance

of the extraction of nitrogen from the air for the lives of all of us.

Unfortunately the author largely ignores other important developments that

were essential for the effective utilization of synthetic nitrogen.

Together with important innovations in plant breeding, the availability of low

cost nitrogen broke the pattern of low grain yields that had persisted for at

least a century and probably longer. The world is a very different place as a



Austin, Roger B. and Michael H. Arnold (1989), “Variability of Wheat Yields in

England: Analysis and Future Prospects,” in Jock R. Anderson and Peter B. R.

Hazell, editors, Variability of in Grain Yields. Baltimore: Johns

Hopkins University Press, pp. 100-106.

Gray, L. C., et al (1924), “The Utilization of our Land for Crops, Pasture and

Forest,” in United States Department of Agriculture, Yearbook of

Agriculture 1923. Washington, DC: Government Printing Office.

United States Department of Agriculture (1962), Agricultural Statistics

1962. Washington, DC: Government Printing Office.

D. Gale Johnson is the Eliakim Hastings Moore Distinguished Service Professor

of Economics Emeritus at the University of Chicago. He is the author of

World Agriculture in Disarray, revised edition 1991 and “Agricultural

Adjustment in China: Problems and Prospects,” Population and Development

Review, Vol. 26, No. 2, June 2000.