Full Planet, Empty Plates by Lester R. Brown

Full Planet, Empty Plates by Lester R. Brown

Author:Lester R. Brown
Language: eng
Format: mobi, epub
Publisher: W. W. Norton & Company
Published: 2012-08-29T04:30:00+00:00

7

Grain Yields Starting to Plateau

From the beginning of agriculture until the mid-twentieth century, growth in the world grain harvest came almost entirely from expanding the cultivated area. Rises in land productivity were too slow to be visible within a single generation. It is only within the last 60 years or so that rising yields have replaced area expansion as the principal source of growth in world grain production.

The transition was dramatic. Between 1950 and 1973 the world’s farmers doubled the grain harvest, nearly all of it from raising yields. Stated otherwise, expansion during these 23 years equaled the growth in output from the beginning of agriculture until 1950. The keys to this phenomenal expansion were fertilization, irrigation, and higher-yielding varieties, coupled with strong economic incentives for production.

The first country to achieve a steady, sustained rise in grain yields was Japan, where the yield takeoff began in the 1880s. But for a half-century or so, it was virtually alone. Not until the mid-twentieth century did the United States and Western Europe launch a steady rise in grain yields. Shortly thereafter many other countries succeeded in boosting grain yields.

The average world grain yield in 1950 was 1.1 tons per hectare. In 2011, it was 3.3 tons per hectare—a tripling of the 1950 level. Some countries, including the United States and China, managed to quadruple grain yields, and all within a human life span.

Some of the factors influencing grain yields are natural, while others are of human origin. Natural conditions of inherent soil fertility, rainfall, day length, and solar intensity strongly influence crop yield potentials. Several areas of cropland with inherently high fertility are found widely scattered around the world: in the U.S. Midwest (often called the Corn Belt), Western Europe, the Gangetic Plain of India, and the North China Plain. It is the incredibly deep and rich soils of the U.S. Midwest that enables the United States to produce 40 percent of the world corn crop and 35 percent of the soybean crop. The state of Iowa, for instance, produces more grain than Canada and more soybeans than China.

The area west of the Alps, stretching across France to the English Channel and up to the North Sea, is also naturally very productive land, enabling densely populated Western Europe to produce an exportable surplus of wheat.

The region in northern India spanning the Punjab and the Gangetic Plain is India’s breadbasket. And the North China Plain produces half of China’s wheat and a third of its corn.

Aside from inherent soil fertility, the level and timing of rainfall, which vary widely among geographic regions, also strongly influence the productivity of land. Much of the world’s wheat, which is drought-tolerant, is grown without irrigation in regions with relatively low rainfall. Most wheat in the United States, Canada, and Russia, for example, is grown under these dryland conditions. Wheat is often grown in areas too dry or too cold to grow corn or rice.

Another natural factor that plays a major role in crop yields is day length.



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