Agriculture

Agriculture is the practice of raising crops or livestock to serve human needs. The term is often used interchangeably with "farming," especially regarding the production of domesticated plant or animal species.

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. Developments in agriculture are often credited with driving or underpinning major trends in human history, such as the establishment of civilizations, urbanization, and globalization.

Historical Overview

The earliest attempts to grow crops are thought to have been 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, which involves clearing a field, burning the trees and brush, and then farming the field. After a few years soil nutrients become depleted, so the process must be repeated at a new location. This type of agriculture is still practiced in some areas, although many agricultural scientists have criticized its environmental impact, especially when carried out at a large scale.

Until the nineteenth century, most farms and ranches were family owned, and most farmers practiced subsistence agriculture: each farmer produced a variety of crops sufficient to feed their family, as well as a small excess that could be 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 labor 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 in 1833, and John Lane and John Deere began the commercial manufacture of the steel plow in 1837. 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 enterprises in developed countries such as the United States were mechanized. Western society was transformed from an agrarian society into an urban society (and the Western vision of industrial agriculture was increasingly pushed on non-Western societies, as well). Fewer people were required to produce the growing amounts of agricultural products that supplied an increasing number of consumers. Many people involved in agricultural production left farms to go to cities to work in factories.

As populations continued to grow, there was a need to select and produce crops with higher yields. The Green Revolution of the twentieth century helped make these higher yields possible. Basic information supplied by biological scientists allowed agricultural scientists to develop new, higher-yielding varieties of numerous crops, particularly the seed grains that supply most of the calories necessary for maintenance of the world’s population. These higher-yielding crop varieties, along with improved farming methods, resulted in tremendous increases in the world’s food supply.

The new crop varieties also led to an increased reliance on monoculture. While the practice of growing only one crop over a vast number of acres resulted in much higher yields, it also decreased the genetic variability of many agricultural plants, increased the need for commercial fertilizers, and produced an increased susceptibility to damage from a host of biotic and abiotic factors. These latter two developments resulted in a tremendous growth in the agricultural chemical industry. By the twenty-first century, the typical modern agricultural unit required relatively few employees, was highly mechanized, devoted large amounts of land to the production of only one crop, and was highly reliant on agricultural chemicals such as fertilizers and pesticides. This style of agriculture allows intensive production to meet globalized demands, but has faced various environmental, economic, and political critiques. As a result, some agricultural scientists and other experts have supported a resurgence of interest in small-scale, localized farming.

Agricultural Diversity

Modern agriculture is subdivided into many different specialties. Those agricultural industries that deal with plants include agronomy, or the production of field crops; forestry, the growth and production of trees and other forest products; and horticulture. Horticulture is subdivided into pomology, the growth and production of fruit crops such as oranges and apples; olericulture, the growth and production of vegetable crops; landscape horticulture, the growth and production of trees and plants that are used in landscape design; and floriculture, the growth and production of flowering plants used in the floral industry.

The various agriculture industries produce a tremendous number of agricultural products. Those derived from plants are often broadly subdivided into timber products (lumber, furniture), grain products (such as wheat and oats), fiber products (cotton, flax, etc.), fruit products (grapes, peaches), nut crops (pecans, hazelnuts), vegetable products (lettuce, cabbage), beverage products (tea, coffee), spice and drug crops (garlic, mustard, opium, quinine), ornamental crops (carnations, chrysanthemums), forage crops (alfalfa, clover), and other cash crops such as sugarcane, tobacco, artichokes, and rubber.

Animal agriculture can also be organized into different branches or disciplines, depending on perspective. Most types are considered under the umbrella of animal husbandry. Domesticated animals used in agriculture are often referred to as livestock, and may be kept for meat, milk, fibers, or other products. Common examples of livestock include cattle, goats, pigs, poultry, and sheep. Farming of fish and other aquatic species is known as aquaculture. Other animals such as honeybees can also be farmed.

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. Soil is one of the most overlooked and misunderstood resources. Most people think of soil as an inert medium from which plants grow. In reality, topsoil—the upper 15 to 25 centimeters (6 to 10 inches) of the earth’s terrestrial surface in which nearly all plants grow—is a complex mixture of weathered mineral materials from rocks, partially decomposed organic molecules, and a large number of living organisms.

The process of soil formation is very slow. Under ideal conditions, enough topsoil can form in one year to produce a layer of about 1 millimeter (0.04 inch) thick when spread over 1 hectare (2.5 acres). With proper management, topsoil can be kept fertile and productive indefinitely. Unfortunately, many agricultural techniques lead to the removal of trees and shrubs, which provide windbreaks, or to the depletion of soil fertility, which reduces the plant cover over the field. These practices expose the soil to increased erosion from wind and moving water. It was reported in 2007 that croplands worldwide are losing soil at a rate between ten and forty times faster than it can be replaced.

Water and Irrigation

Because plants require water in order to grow, agriculture represents the largest single use of global water. Irrigation accounts for about 70 percent of all freshwater withdrawn from groundwater supplies, rivers, and lakes and about 90 percent of all water consumption, as reported by S. Siebert and colleagues in 2010. According to the Food and Agriculture Organization of the United Nations (FAO), irrigated agricultural land accounts for about 20 percent of all cultivated land worldwide.

Water use varies among countries. Some countries have abundant water supplies and irrigate liberally, while water is very scarce in other countries and must be used very carefully. Because as much as 80 percent of the water intended for irrigation is lost to evaporation before reaching the plants, the efficiency of water use in some countries can be very low.

There is no doubt that irrigation has dramatically increased crop production in many areas, but some irrigation practices have been detrimental. Overwatering can lead to a waterlogging of the soil. Waterlogging cuts off the supply of oxygen to the roots, and the plants die. Irrigation of crops in dry climates can often result in salinization of the soil. In these climates, the irrigation water rapidly evaporates from the soil, leaving behind mineral salts that were dissolved in the water. As the salts accumulate, they become lethal to most plants. According to the FAO, about thirty-seven million hectares of irrigated cropland worldwide have been damaged by salinization. There is also debate whether the increased usage of water for agriculture has decreased the supply of potable water fit for other uses.

Fertilizers

Plants require sunshine, water either from rainfall or irrigation, carbon dioxide from the atmosphere, and thirteen mineral nutrients from the soil. Of these nutrients, calcium, magnesium, nitrogen, phosphorus, and potassium are required in the greatest amounts. Calcium and magnesium are plentiful in soils located in dry climates, but in wetter climates these nutrients are often leached through the soil. In these regions, calcium and magnesium are returned to the soil in the form of lime, which is also sometimes added to soil to raise its pH (increase its alkalinity). Nitrogen, phosphorus, and potassium, often referred to as the "fertilizer elements," are the nutrients that are most often depleted from agricultural soils. Because these nutrients stimulate plant growth and can greatly increase crop yields, it is necessary to apply them to the soil regularly in order to maintain fertility.

The amount of fertilizer applied to the soil increased more than 450 percent in the second half of the twentieth century. While this increase in the use of fertilizers has more than doubled worldwide crop production, it has also caused some problems. The increased production of fertilizers has required the use of energy and mineral resources that could have been used elsewhere. Studies have suggested that farmers tend to overfertilize. Overfertilization not only wastes money but also contributes to environmental degradation. Fertilizer elements, particularly nitrogen and phosphorus, are carried away by water runoff and are eventually deposited in the rivers and lakes, where they contribute to pollution of aquatic ecosystems.

Other Resources

Modern industrial agriculture consumes large amounts of energy. Farm machinery used in planting, cultivating, harvesting, and transporting crops to processing plants or to market consumes large supplies of liquid fossil fuels such as gasoline or diesel. The energy required to produce fertilizers, pesticides, and other agricultural chemicals is the second-largest energy cost associated with agriculture. The use of fuel required by pumps to irrigate crops is also a major energy consumer. Additional energy is used in food processing, distribution, storage, and cooking after the crop leaves the farm. The energy used for these activities may be five times as much as that used to produce the crop. Some studies have found that many foods consumed in developed nations such as the United States require more calories of energy to produce, process, and distribute to the market than they provide when they are eaten.

Such findings, combined with growing scientific concern over climate change and other environmental degradation linked to industrial activity, have spurred efforts to develop more sustainable agriculture. Many observers have highlighted the potential of using biomolecular techniques to produce new crop varieties. Genetic engineering and related techniques have been investigated to help agricultural scientists develop crops and livestock that can be produced, processed, and distributed with less impact on other resources.

Bibliography

Acquaah, George. Principles of Crop Production: Theory, Techniques, and Technology. 2nd ed., Prentice Hall, 2005.

"Ag and Food Sectors of the Economy." USDA Economic Research Service, US Department of Agriculture, www.ers.usda.gov/data-products/ag-and-food-statistics-charting-the-essentials/ag-and-food-sectors-and-the-economy.aspx. Accessed 15 Oct. 2024.

"AQUASTAT." Food and Agriculture Organization of the United Nations, www.fao.org/aquastat/en/. Accessed 15 Oct. 2024.

Canning, Patrick, et al. Energy Use in the US Food System. Economic Research Report no. 94, Economic Research Service, United States Dept. of Agriculture, 2010. USDA ERS, www.ers.usda.gov/publications/pub-details/?pubid=46377. Accessed 6 Apr. 2017.

Denham, Tim, and Peter White, editors. The Emergence of Agriculture: A Global View. Routledge, 2007.

"The Development of Agriculture." National Geographic, education.nationalgeographic.org/resource/development-agriculture/. Accessed 15 Oct. 2024.

Grigg, David B. An Introduction to Agricultural Geography. 2nd ed., Routledge, 1995.

"History of Agriculture." Food System Primer, Johns Hopkins Center for a Livable Future, foodsystemprimer.org/production/history-of-agriculture. Accessed 15 Oct. 2024.

Janick, Jules. Horticultural Science. 4th ed., W. H. Freeman, 1986.

Pimentel, David. "Soil Erosion: A Food and Environmental Threat." Environment, Development and Sustainability, vol. 8, no. 1, 2006, pp. 119–37.

Siebert, S., et al. "Groundwater Use for Irrigation: A Global Inventory." Hydrology and Earth System Sciences, vol. 14, no. 10, 2010, pp. 1863–80. Food and Agriculture Organization of the United Nations, www.fao.org/documents/card/en/c/77dfb31f-bc59-52fd-b0ee-07d800bc823f/. Accessed 6 Apr. 2017.

Smith, Bruce D. The Emergence of Agriculture. W. H. Freeman, 1995.

Zohary, Daniel, et al. Domestication of Plants in the Old World: The Origin and Spread of Domesticated Plants in Southwest Asia, Europe, and the Mediterranean Basin. 4th ed., Oxford UP, 2012.