A crop is a plant or plant product that can be grown and harvested for profit or subsistence. By use, crops fall into six categories: food crops, feed crops, fiber crops, oil crops, ornamental crops, and industrial crops.

Food crops, such as fruit and vegetables, are harvested for human consumption. Grains, such as corn, wheat, and rice, are the world’s most popular food crops.

Food crops were the first crops to be harvested through agriculture. Agricultural development and the growth of civilizations led to the diversity of other types of crops.

Feed Crops

Feed crops, such as oats and alfalfa, are harvested for livestock consumption. These crops contain nutrients that animals need to develop. They are grown in agricultural fields but can also be found in natural meadows and pastures.

Forage crops are important for livestock farming. Animals feed directly on forages, such as grasses. Forages that are cut and fed to livestock while they are still fresh are called green chop. Alfalfa is a popular crop fed to livestock as green chop.

Some forages are cut, allowed to dry in the field, and stored. These are called hay crops.

Another type of forage crop is silage. Silage crops are harvested, then stored under conditions that allow the forage to break down (ferment) into acids. The wet, acidic silage is fed to livestock such as cattle.

Principle feed crops include corn, barley, wheat, and oats. Each of these crops has different properties that are better suited for some animals’ diets over others. Barley, which is harder to digest, is most often fed to beef and dairy cattle because they have a tough, four-chambered stomach. Hull-less barley, which is easier to digest, is fed to swine and poultry.

The production of feed crops has risen dramatically with increased demand for meat worldwide. Increased production of feed crops has changed the agricultural landscape.

The Food and Agriculture Organization (FAO) says 33 percent of arable land on Earth is used to produce food for livestock. This limits the production of crops for human consumption, especially for the world’s poorest people.

Forests have been cleared to create pastures where livestock can graze. Almost 70 percent of land cleared from the Amazon rainforest, for instance, has been turned over to grazing.

Fiber Crops

Fiber crops, such as cotton and hemp, are harvested for textile and paper products. Textiles, or cloth, are made from the dried and processed fibers of certain plants. Most fibers used to make textiles are taken from the stem or roots of plants such as flax. Flax is used to make linen.

Other parts of a plant can be harvested for fiber. Cotton, the most popular fiber crop in the world, is harvested from the light, fluffy “boll” of fiber that surrounds the plant’s seeds. Textiles made from bamboo are manufactured from the pulp of bamboo plants.

Pulp from other fiber crops can be used in a variety of products. Fiber pulp may be used instead of wood pulp to manufacture paper products.

The hemp plant is an interesting and controversial example of a fiber crop. The fibers of the hemp plant are strong and durable, perfect for products such as paper, textiles, ropes, nets, and sailcloth for ships. Hemp advocates see the plant as a versatile and ecological source of fiber.

But some varieties of the hemp plant are used to make marijuana, a psychoactive drug. Marijuana is illegal to grow and use in many parts of the United States. (The drug is legally grown and sold for medical or recrecational use in some places.) Opponents of hemp argue that increased harvesting of hemp crops will lead to increased production and use of marijuana.

Oil Crops

Oil crops, such as canola and corn, are harvested for consumption or industrial uses. Technologies developed in the past century have enabled crops to be processed and broken down into their primary components, including oil. Soybeans, for example, represented 61 percent of world oilseed production and 79 percent of all edible oil consumed in the United States in 2000.

Oil crops are harvested for use in cooking, such as olive oil and corn oil. Oil crops are also harvested for industrial use, such as oil paints, soaps, and lubrication for machinery.

Fuel made from oil crops is called biofuel. The demand for biofuels has grown in recent years. Rising gas prices, concerns about global warming, and a desire for energy self-sufficiency have led governments and businesses to invest in biofuel research.

There are two main types of biofuel that use oil crops: bioethanol and biodiesel.

Bioethanol is an alcohol made from fermented materials that come from sugar and starch crops. These crops include sugar cane, corn, and wheat. Bioethanol can be used as a fuel for vehicles, but it is usually used as a gasoline additive to improve vehicle emissions. Bioethanol is used widely in the United States and Brazil, where an abundance of corn and sugar cane crops facilitate its production.

Biodiesel is made by combining vegetable oils with alcohol. Nuts, such as coconuts, macadamias, and pecans, are excellent sources of oil used to manufacture biodiesel. Biodiesel can be used in diesel engines, such as those used by buses. Brazil, the United States, and the European Union (particularly Germany) manufacture and use biodiesel on a large scale.

Biofuels provide almost three percent of the world’s transport fuel. Many scientists and economists predict that number will rise as oil production decreases in the next century.

Ornamental Crops

Ornamental crops, such as dogwood and azalea, are harvested for landscape gardening. Ornamental crops are most often grown in nurseries, where they are purchased for residential or commercial settings.

Ornamental crop production has deep historical roots. The tulip crop of the Netherlands, for example, has become a symbol of that country.

Today, ornamental crop production is an important economic activity in many developing countries. Kenya, for example, is a major exporter of roses and carnations. Kenyan flower growers have situated their greenhouses near the shores of Lake Naivasha and Lake Victoria, where the soil is fertile and the water is abundant and fresh.

Kenya’s huge flower operations, however, are having a negative impact on lake ecosystems. Growers irrigate their flowers with lake water, dramatically lowering supplies of freshwater available for consumption and hygiene. Growers also apply heavy amounts of fertilizers and pesticides so their flowers can maintain their beauty throughout the export process. These chemicals often runoff into the lakes, endangering aquatic animal and plant life.

Industrial Crops

Industrial crops, such as rubber and tobacco, are harvested for their products’ use in factories or machines. Industrial crops include all crops used in the production of industrial goods, such as fiber and fuel products.

Rubber is produced naturally from a wide variety of plants, but predominantly from the Hevea tree indigenous to the Amazon region. Rubber is harvested for its latex. Latex is an extremely tough fluid found in the inner bark of the Hevea tree. Latex is obtained by tapping—cutting or shaving the bark with a sharp knife—and collecting the latex in cups. When mixed with chemicals, latex creates solid rubber blobs, called curds. Rubber curds are pressed between rollers to remove excess moisture and to form sheets. The sheets are packed and shipped for use in tires, machine belts, shoe soles, and other products.

Rubber has been used by civilizations for thousands of years. One of the earliest uses of rubber was to create balls for use in games in the Olmec Empire in what is today Mexico. Today, rubber is still used to manufacture durable toys, as well as boots, flooring, balloons, and medical supplies.

Hevea trees transplanted to southern Asia now produce most of the world’s rubber. The countries with the largest rubber crops are Thailand, Indonesia, and Malaysia. Industrialization around the world has increased the global demand for rubber. High demand for natural rubber has increased the environmental degradation of forests in southern Asia.

Harvesting Crops

Methods for growing and harvesting crops have developed over thousands of years. The earliest crops were grown in Mesopotamia around 5500 B.C.E. These crops, indigenous to an agriculturally rich area called the Fertile Crescent, were grown near local sources of freshwater so they could be irrigated relatively easily. Wheat, barley, and figs were among the first crops.

The development of agriculture led to more sophisticated methods of harvesting crops. Crop rotation was the most significant innovation. In crop rotation, one crop is planted one year, then a different crop is planted the next year on the same land. This helps preserve the soil and reduce the chance for disease.

Crop rotation and fertilization, which makes soil more productive, allowed farmers to grow more crops on less land. These innovations also allowed crops to be grown in areas where they might not grow naturally. Improved engineering allowed rivers to be dammed and diverted to provide water for crops. All of these developments increased the abundance of crops, which could be used for trade and industrial use.

Today, agriculture is the largest industry in the world. Millions of people harvest crops for subsistence or business purposes. Some tools used to harvest crops have not changed in a thousand years—plows, rakes, sickles. Most of all, harvesting crops still relies on human labor.

The tools and machinery used to harvest crops have grown much more complex and expensive, however. Fertilizers, which many farmers need to be economically competitive, cost more than many farmers in the developing world can afford. Machinery, such as tractors and plows, can cost hundreds of thousands of dollars.

GMOs

Genetically modified organisms (GMOs or GM foods) are common throughout the developed world. Biotechnology allows scientists to alter the DNA of microbes, plants, and animals. Businesses sell farmers genetically modified seeds. With these seeds, farmers can use toxic chemicals without harming the crop. Farmers who grow GM foods increase production with less labor and less land. Vegetables and fruits last longer and are less likely to bruise.

The heavy reliance on chemicals has disturbed the natural environment, however. Helpful species of animals may be killed along with harmful ones. Chemical use may also pose a health hazard to people, especially through runoff entering local aquifers and other water supplies. Critics argue that GM foods have less nutritional value and decrease biodiversity.

Organic and free-range food industries have grown in opposition to industrial farming. Agricultural scientists are looking for safer chemicals to use as fertilizers and pesticides. Some farmers use natural controls and rely less on chemicals.

Seed Banks

In order to preserve biodiversity, seed banks have been created around the world to store seed samples. Seed banks may specialize in a specific crop or in the crops of a region. The International Potato Center, based in Lima, Peru, houses 150 wild potato species and other tubers of Andean origin.

Native Seeds, founded in the southwestern United States, helps Native Americans locate seeds for growing traditional crops, such as orach, or “mountain spinach,” and amaranth, once widely used for food and fiber in Mexico.

The Svalbard Global Seed Vault, the world’s most diverse seed bank, was established in 2008. The Norwegian government built the Seed Vault into the side of a permafrost-covered mountain on the island of Spitsbergen, part of the Svalbard archipelago about 1,030 kilometers (620 miles) from the North Pole. The vault is designed to safely store the seeds of hundreds of thousands of plant varieties from crops grown throughout the globe. The Seed Vault offers “fail-safe” protection for the world’s agricultural inheritance against any natural, social, or economic disaster.

Today, the Seed Vault stores about one million seed samples. It has the capacity to hold 4.5 million samples.

Crops have a wide variety of uses and are an integral part of our existence and development. While advancements in crop science and technology have increased the production of some of our most basic foodstuffs, they also have had wide-ranging impacts on the environment.

The production of crops does not have to harm the environment. By protecting the land, water, and air, and by sharing knowledge and resources, people may find solutions for the problems of world hunger and global energy scarcities through the sustainable use of crops.