Agriculture is the art and science of cultivating the soil, growing crops, and raising livestock. It includes the preparation of plant and animal products for people to use and their distribution to markets.

Agriculture provides most of the world’s food and fabrics. Cotton, wool, and leather are all agricultural products. Agriculture also provides wood for construction and paper products.

These products, as well as the agricultural methods used, may vary from one part of the world to another.

Start of Agriculture

Over centuries, the growth of agriculture supported the development of cities. Before agriculture became widespread, hunting and gathering was how people fed themselves. Between 10,000 and 12,000 years ago, people gradually learned how to grow cereal and root crops, and settled down to a life based on farming.

Eventually, much of Earth’s population became dependent on agriculture. Scholars are not sure why this shift to farming took place, but it may have occurred because of climate change.

When people began growing crops, they also continued to adapt animals and plants for human use. Adapting wild plants and animals for people to use is called domestication. Hunter-gatherers began to domesticate animals and change the natural environment to grow more food even before settled farming became widespread.

Barley, wheat, legumes, vetch, and flax were among the first plants to be domesticated.

The first domesticated animals were dogs, which were used for hunting. Sheep and goats were probably domesticated next. People also domesticated cattle and pigs. The predecessors of most of these animals had once been hunted for hides and meat. Many of them also became sources of milk, cheese, and butter. Eventually, people used domesticated animals such as oxen for plowing, pulling, and transportation.

Agriculture enabled people to produce surplus food. They could use this extra food when crops failed or trade it for other goods.

Agriculture kept formerly nomadic people near their fields and led to the development of permanent villages. These became linked through trade. New economies were so successful in some areas that cities developed. The earliest societies based on intensive agriculture arose in the Fertile Crescent (which spans the Levant, modern-day Turkey, and Iran) and along the Nile River in Egypt. Other very early agricultural societies developed independently in Central America, East Asia, the Indus Valley, and West Africa.

Improved Technology

Many effective agricultural techniques have roots in pre-agricultural human history. For millennia, people have used controlled burning techniques to get rid of brush and debris, allowing edible plants to grow more abundantly and preventing larger wildfires during dry seasons. Today, large wildfires in North America and Australia demonstrate the importance of maintaining controlled burning practices perfected by many Native American tribes and Aboriginal Australian peoples.

Farming has also improved over the years. Early farmers cultivated small plots of land by hand, using axes to clear away trees and digging sticks to break up and till the soil. Over time, improved farming tools of bone, stone, bronze, and iron were developed. New methods of storage evolved. People began stockpiling foods in jars and clay-lined pits for use in times of scarcity. They also began making clay pots and other vessels for carrying and cooking food.

Around 5500 B.C.E., farmers in Mesopotamia developed simple irrigation systems. By channeling water from streams onto their fields, farmers were able to settle in areas once thought to be unsuited to agriculture. In Mesopotamia, Egypt, and China, people organized themselves and worked together to build and maintain better irrigation systems.

Early farmers also developed improved varieties of plants. For example, around 6000 B.C.E., a new variety of wheat arose in South Asia and Egypt. It was stronger than previous cereal grains, its hulls were easier to remove, and it could be made into bread.

As the Romans expanded their empire using warfare and coercion, they wrote manuals about the farming techniques they observed in Africa and Asia, and adapted them to land in Europe.

In China, farmers also adapted tools and methods from nearby empires. A variety of rice from Vietnam ripened quickly and allowed farmers to harvest several crops during a single growing season. This rice quickly became popular throughout China.

Many medieval European farmers used an open-field system of planting. One field would be planted in spring, another in autumn, and one would be left unplanted, or fallow. This system preserved nutrients in the soil, increasing crop production.

The leaders of the Islamic Golden Age (which reached its height around 1000 C.E.) in North Africa and the Middle East made agriculture into a science. Islamic Golden Age farmers learned crop rotation.

In the 15th and 16th centuries, explorers introduced new varieties of plants and agricultural products into Europe. From Asia, they carried home coffee, tea, and indigo, a plant used to make blue dye. From the Americas, they took plants such as potatoes, tomatoes, corn (maize), beans, peanuts, and tobacco. Some of these became staples and expanded people’s diets.

Machinery

A period of important agricultural development began in the early 1700s for Great Britain and the Low Countries (Belgium, Luxembourg, and the Netherlands, which lie below sea level). New agricultural inventions dramatically increased food production in Europe and European colonies, particularly in North America.

One of the most important of these developments was an improved horse-drawn seed drill invented by Jethro Tull in England. Until that time, farmers sowed seeds by hand. Tull’s drill made rows of holes for the seeds. By the end of the 18th century, seed drilling was widely practiced in Europe.

Many machines were developed in the United States. The cotton gin, invented by Eli Whitney in 1794, reduced the time needed to separate cotton fiber from seed. The invention of the cotton gin was not without negative consequences, however: as cotton became more profitable and less labor-intensive, enslavers had incentive to buy more enslaved people to produce more cotton.

In the 1830s, Cyrus McCormick’s mechanical reaper helped modernize the grain-cutting process. At about the same time, John and Hiram Pitts introduced a horse-powered thresher that shortened the process of separating grain and seed from chaff and straw. John Deere’s steel plow, introduced in 1837, made it possible to work the tough prairie soil with much less horsepower. Along with new machines, there were several important advances in farming methods. By selectively breeding animals (breeding those with desirable traits), farmers increased the size and productivity of their livestock.

Cultures have been breeding animals for centuries. Ancestors of modern sheep, goats, cattle, and pigs were the first livestock to be bred selectively. Farmers began to practice selective breeding on a large scale beginning in 18th century Europe. An early example of this is the Leicester sheep, an animal selectively bred in England for its quality meat and long, coarse wool.

Plants could also be selectively bred for certain qualities. In 1866, Gregor Mendel’s studies in heredity were published in Austria. In experiments with pea plants, Mendel learned how traits were passed from one generation to the next. His work paved the way for improving crops through genetics.

New crop rotation methods also evolved during this time. Many of these were adopted over the next century or so throughout Europe. For example, the Norfolk four-field system, developed in England, proved quite successful. It involved the yearly rotation of several crops, including wheat, turnips, barley, clover, and ryegrass, and livestock management practices, in which animals grazed in selected fields and left animal waste behind. This added nutrients to the soil, enabling farmers to grow enough to sell some of their harvest without having to leave any land unplanted.

Agricultural Science

Between 1960 and 2000, staple crop yields in low- and middle-income countries like Mexico and India increased substantially. How did this great leap in productivity come about? It happened largely because of scientific advances and the development of new sources of power.

By the late 1950s, most farmers in high-income countries were using both gasoline and electricity to power machinery. Tractors had replaced draft animals and steam-powered machinery. Farmers were using machines in almost every stage of cultivation and livestock management.

Electricity first became a power source on farms in Japan and Germany in the early 1900s. By 1960, most farms in the U.S. and other high-income countries were electrified. Electricity lit farm buildings and powered such machinery as water pumps, milking machines, and feeding equipment. Today, electricity controls entire environments in livestock barns and poultry houses.

Traditionally, farmers have used a variety of methods to protect their crops from pests and diseases. They have put herb-based poisons on crops, handpicked insects off plants, bred strong varieties of crops, and rotated crops to control insects. Now, almost all farmers, especially in high-income countries, rely on chemicals to control pests. The definition of “pest” ranges from insects to animals such as rabbits and mice, as well as weeds and disease-causing organisms—bacteria, viruses, and fungi. With the use of chemicals, crop losses and prices have declined dramatically.

For thousands of years, farmers relied on natural fertilizer—materials such as manure, wood ash, ground bones, fish or fish parts, and bird and bat waste called guano—to replenish or increase nutrients in the soil. Some farmers, particularly those that grow organic crops, still use natural fertilizers.

In the early 1800s, scientists discovered which elements were most essential to plant growth: nitrogen, phosphorus, and potassium. Now, many farmers use chemical fertilizers with nitrates and phosphates because they greatly increase crop yields.

However, pesticides and fertilizers have come with another set of problems. The heavy reliance on chemicals has disturbed the environment, often contaminating the surrounding soil and water while being toxic to birds, fish, and other species that farmers do not intend to target. Chemical use may also pose a health hazard to people, especially through contaminated water supplies. Agricultural scientists are looking for safer chemicals to use as fertilizers and pesticides. Some farmers use natural controls and rely less on chemicals.

Farming in Water

Agriculture includes such forms of cultivation as hydroponics and aquaculture. Both involve farming in water.

Hydroponics is the science of growing plants in nutrient solutions. Just one acre of nutrient solution can yield more than 50 times the amount of lettuce grown on the same amount of soil.

Aquaculture—primarily the cultivation of fish and shellfish—was practiced in China, India, and Egypt thousands of years ago. It is now used in lakes, ponds, the ocean, and other bodies of water throughout the world. Some forms of aquaculture, such as shrimp farming, have become important industries in many Asian and Latin American countries.

Climate change and improved technology are altering the way freshwater and ocean fisheries operate. Global warming has pushed warm-water species toward the poles and reduced the habitats of cold-water species. Traditional fishing communities in both developed and developing countries find the number of fish dwindling.

Bottom trawling has affected ocean ecosystems. In bottom trawling, enormous nets are strung from fishing boats and dragged at the bottom of the ocean. The nets catch halibut and squid, but also stir up sediment at the bottom of the ocean. This disturbs the marine life (plankton and algae) that forms the basis of the food chain.

Genetic Modification

For centuries, people have bred new types of plants and animals through experimentation. During the 1950sand 1960s, scientists developed new strains of high-yield wheat and rice. They introduced them into Mexico and parts of Asia. As a result, production of grain soared in these areas. This bold experiment in agriculture has been called the "Green Revolution."

With the successes of the Green Revolution came problems. To produce high yields, the new strains required chemical fertilizers, pesticides, and irrigation. In many low- and middle-income countries, independent farmers cannot afford the new technology and big business has taken over agriculture. The new, high-production crops also put stress on native plants and animals.

Later, scientists and farmers understood how the new strains developed. This gave rise to a new green revolution: genetic modification of food.

Inside every cell are genes, material that determines many of the characteristics of an organism. Genetics is the study of what characteristics organisms inherit and how these traits are transmitted. With a greater knowledge of genetics, people can scientifically select characteristics they want to reproduce. New technology has revolutionized the selective breeding process in both plants and animals.

Beginning in the 1970s, scientists found that they could rearrange genes and add new ones to promote disease resistance, productivity, and other desired characteristics in crops and livestock. These genetically modified organisms (GMOs or GM foods, referred to as bioengineered foods in the United States) are now common throughout the developed world. Biotechnology allows scientists to alter the DNA of microbes, plants, and animals. GMOs that have genetic material, or DNA, from other species are called transgenic organisms.

A gene from an Arctic plant, for example, could be added (spliced) into the DNA of a strawberry plant to increase the strawberry’s resistance to cold and thus extend its growing season. The strawberry would be a transgenic plant.

Biotechnology has brought advances in animal husbandry (ranching, or the raising of domestic animals). Today’s farm animals are larger and grow faster than their predecessors.

Cattle, for example, are grazing animals. Their digestive system has evolved to process grasses and other crops. Corn and other grains cause a cow’s digestive system to become acidic. That makes it easier for dangerous bacteria (such as E.coli) to develop. Bacterial infections can be harmful to the cow, and can also infect their milk and meat consumed by people. Antibiotics have been used since the 1950s to stimulate cattle growth and prevent infection. Over time, this practice has led to the development of antibiotic-resistant bacteria in cattle and people. Many cattle are also given anabolic steroids, or growth hormones, to make them get bigger, faster.

Most of the world’s farmers live in low- and middle-income countries in Africa, Asia, and Latin America. Some of them cultivate land as their ancestors did hundreds or even thousands of years ago. They may not use agricultural technology involving expensive chemicals or production methods.

Many of the world’s farmers are subsistence farmers. They use the bulk of the food they produce for themselves and their families, unlike commercial farmers, who only grow crops to sell.

Methods of Cultivation

Agricultural methods often vary widely around the world, depending on climate, terrain, traditions, and available technology.

Low-technology farming involves permanent crops: food grown on land that is not replanted after each harvest. Citrus trees and coffee plants are examples of permanent crops. Higher-technology farming involves crop rotation, which requires knowledge of farmable land. Scholars and engineers not only use crop rotation and irrigation, but plant crops according to the season, type of soil, and amount of water needed.

In coastal West Africa, farmers, usually women, plant corn soon after the first rains of the growing season. They often use an ancient method of clearing called slash-and-burn. First, the farmer cuts all the brush in her plot. When this vegetation dries, she sets fire to it. The heat from the fire makes the soil easy to turn, and the burned vegetation fertilizes it. The farmer then sows kernels of corn saved from the previous year’s harvest.

Between rows of corn, the coastal West African farmer plants other staple crops: legumes, such as peas, or root vegetables, such as yams. This practice of growing several crops in the same plot is called intercropping. By covering most of the ground with vegetation, intercropping prevents moisture loss and soil erosion from seasonal rains.

Rain supplies water for the growing plants. The farmer weeds her plot with a hoe. At harvest time, she and her family pick the corn, husk it, and spread the ears in the sun to dry. They grind the dried corn to make porridge.

Traditionally, the coastal West African farmer uses the same plot for several years, until its fertility declines. Then she moves to another plot, leaving the first to lie fallow for up to 10 years. Now, an increasing population has caused fallow periods to be reduced and has made permanent cultivation more common.

Agricultural methods used in the Corn Belt of the U.S. are very different. The Corn Belt is the area of the northern Midwest where most of the nation’s corn crop is grown. First of all, farmers rarely work alone—the size of U.S. farms requires a lot of labor. Soon after they harvest the corn in autumn, farmers work leftover vegetation, or stubble, into the soil. In the spring, farmers work the soil again, using an implement with rows of sharp-edged steel discs, called a disc harrow. The discs cut into the soil, breaking it into smaller pieces and supplying it with air.

Next, a tractor-pulled planter sows rows of seed. The machine makes furrows in the soil, drops in kernels of high-yield, genetically modified corn, and covers them with dirt. After the corn seeds have sprouted, another machine injects liquid fertilizer into the ground.

The farmers then use chemicals to control weeds and pests, and loosen the soil with a tractor-pulled cultivator during the harvesting season.

U.S. industrial farmers may plant a thousand acres of just corn. The practice of specializing in a single crop is known as monoculture. To harvest the crop, farmers use a mechanical harvester that picks the ears of corn and shells them into a bin.

Little of the corn grown in the Corn Belt is for human consumption. Most of the corn grown in the U.S. is for cattle feed and industrial uses, such as corn syrup sweeteners.

Livestock

From alpacas in Peru to zebus in India, billions of domesticated animals around the world are raised and cared for in a variety of ways. In many countries, domesticated animals are an important source of food.

In Nigeria, for example, the Fulani people have long been pastoralists and nomads. They move with their cattle herds from one grazing area to another. The cattle feed on scrub and grasses in land unsuitable for farming. The Fulani rely on cattle for milk, but rarely slaughter their animals for meat.

Throughout the U.S., beef cattle are bred to grow quickly and yield large quantities of fatty meat. When they are five to 12 months old, the animals are shipped to feedlots. There, they are kept in pens and fed grain and vitamin supplements until they reach market size. Then they are slaughtered.

The two ways of raising livestock are confronting each other in low- and middle-income countries. In Uganda, Ankole cattle have been bred to withstand the variable climate—their long, curved horns help distribute heat and their digestive systems have adapted to poor nutrition and little water during dry seasons. However, the market for milk has driven many Ugandan farmers to import Holstein cattle. Holsteins are native to Northern Europe. Keeping them healthy in an equatorial region requires a high amount of antibiotics, vaccines, and other chemicals. The Ankole, which produce little milk and leaner meat, may be extinct within the century.

Many farmers throughout the world practice free-range poultry farming. The birds forage for food in farms or community yards, eating whatever they find: seeds, insects, household scraps, and surplus grain.

In many high-income countries, poultry production has become a major agricultural industry. Birds are given the same sort of vaccines and hormones used for cattle. Chickens are bred for either eggs or meat. One poultry house may contain more than a million birds. Often, machines automatically provide feed and water, collect the eggs, and remove waste.

Sustainability and Food Justice

In the decades following the beginning of the Green Revolution, agricultural food production has increased dramatically. Unfortunately, there are drawbacks to the farming methods and technologies that allow for this increase.

One problematic feature of industrial agriculture is land use: half of the habitable land on Earth is currently used for farming. Land that used to be home to biodiverse ecosystems has been cleared for agricultural use, and many commercial farms use monoculture farming. Though monoculture farms produce more staple crops like wheat and corn, they are more susceptible to disease, lack biodiversity, and deplete nutrients in the soil.

Another issue with industrial farming is the overuse of fertilizers, particularly fertilizers that use nutrients like nitrogen and phosphorus. Over the past 35 years, the use of nitrogen and phosphorus fertilizers has increased dramatically. Crops only use about one-third of the nitrogen and less than half of the phosphorus applied to them; the rest of that nitrogen and phosphorus becomes runoff that pollutes the surrounding ecosystem. This nutrient pollution creates “dead zones” in aquatic ecosystems through a process called eutrophication: algae feed on the nitrogen and phosphorus, causing algal blooms. When the excess algae die, the bacteria that decompose the dead algae use up the water’s oxygen supply, suffocating fish and other aquatic organisms.

Though irrigation allows farmers to grow crops on land that otherwise would not be usable for agriculture, it also poses a threat to the environment. Irrigation requires significant land and water use; around 70 percent of freshwater withdrawal around the world is attributed to agricultural irrigation, and only about half of this water can be reused. Building dams and reservoirs for irrigation has destroyed many ecosystems in and around lakes and rivers. Irrigation can also introduce excess salt to soil and groundwater, negatively impacting both drinking water and plants in the surrounding area.

Currently, food production is the second-largest contributor to greenhouse gas emissions. Land, water, and air alike are all threatened by industrial agriculture, yet an estimated two billion people around the world still suffer from malnutrition. The issue is not that the agriculture industry does not produce enough food, but rather that the food supply is unevenly distributed. Many people cannot afford to eat enough, and those that can afford sufficient nutrition frequently waste food; one trillion dollars’ worth of food is wasted around the world every year. Experts say that if corporations and consumers in the richest countries stopped wasting food, we could save enough to feed an extra two billion people—the same portion of the population that is currently malnourished.

The fight against hunger and the fight for sustainable food systems are deeply connected. In order to meet a growing global population’s nutritional needs, the agricultural sector needs to shift its focus to environmentally sustainable food production. This may require a switch from industrial agriculture to permaculture, an ecological design system that mimics naturally existing, biodiverse environments while optimizing food production. In the meantime, corporations and governments need to collaborate to minimize food waste and provide affordable nutrition to those that buy the majority of their food, while providing economic assistance to small subsistence farmers in rural areas of low- to middle-income countries. By protecting the land, water, and air, and by sharing knowledge and resources, people may yet find solutions for the problems of world hunger and industrial agriculture.