The beginnings of agriculture predate written history. No one knows when the first crop was cultivated, but at some time in the distant past humans discovered that seeds from certain wild grasses could be collected and planted in land that could be controlled and the grasses later gathered for food. Most scholars believe this occurred at about the same time in both the Eastern and Western Hemispheres, some eight thousand to ten thousand years ago.
Early Agriculture
The earliest attempts to grow crops were primarily to supplement the food supply provided by hunting and gathering. However, as the ability to produce crops increased, people began to domesticate plants and animals, and their reliance on hunting and gathering decreased, allowing the development of permanent settlements in which humans could live. As far back as six thousand years ago, agriculture was firmly established in Asia, India, Mesopotamia, Egypt, Mexico, Central America, and South America.
The earliest agricultural centers were located near large rivers that helped maintain soil fertility by the deposition of new topsoil with each annual flooding cycle. As agriculture moved into regions that lacked the annual flooding of the large rivers, people began to utilize a technique known as slash-and-burn agriculture. In this type of agriculture, a farmer clears a field, burns the tress and brush, and farms the field. After a few years soil nutrients become depleted, so the farmer must repeat the process at a new location. This type of agriculture is still practiced in some developing countries and is one reason tropical rain forests are disappearing at a fast rate.
Until the nineteenth century, most farms and ranches were family owned, and most farmers practiced sustenance agriculture: Each farmer produced a variety of crops sufficient to feed his or her family as well as a small excess which was sold for cash or bartered for other goods or services. Agricultural tools such as plows were made of wood, and almost all agricultural activities required human or animal labor. This situation placed a premium on large families to provide the help needed in the fields.
The arrival of the Industrial Revolution changed agriculture, just as it did almost all other industries. Eli Whitney invented the cotton gin in 1793. The mechanical reaper was invented by Cyrus McCormick, and John Lane and John Deere began the commercial manufacture of the steel plow in 1833 and 1837, respectively. These inventions led the way to the development of the many different types of agricultural machinery that resulted in the mechanization of most farms and ranches. By the early part of the twentieth century, most agricultural en terprises in the United States were mechanized. American society was transformed from an agrarian society into an urban society. People involved in agricultural production left farms to go to cities to work in factories. At the same time, there was no longer a need for large numbers of people to produce crops. As a result, fewer people were required to produce the growing amounts of agricultural products that supplied an increasing number of consumers.
Modern Agriculture
As populations continued to grow, there was a need to select and produce crops with higher yields.
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Agricultural Diversity
Modern agriculture is subdivided into many different specialties.
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Impact on Soil Resources
While there have been tremendous increases in agricultural productivity through the use of modern agricultural practices, these practices have had a significant impact on some other natural resources.
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Water and Irrigation
Because plants require water in order to grow, agriculture represents the largest single use of global water.
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Fertilizers
Plants require sunshine, water either from rainfall or irrigation, carbon dioxide from the atmosphere, and thirteen mineral nutrients from the soil.
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Other Resources
Modern agriculture, as it is practiced in the United States, consumes large amounts of energy.
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Commercial Impact
While fewer than 1 percent of Americans are directly involved in agricultural production, agriculture in the United States employs about seventeen million people in some phase of the industry, from production to retail sales.
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