Crop Farming

I

Introduction

Crop Farming, extensive cultivation of plants to yield food, feed, or fiber; to provide medicinal or industrial ingredients; or to grow ornamental products. Crop farming developed in ancient times as hunters and gatherers of the Stone Age turned to the cultivation of favored species (see Agriculture). Modern crops were gradually derived from their wild ancestors through continual selection for larger seed size, improved fruit, and other desired traits.

Modern crops evolved in the regions of their ancient centers of origin. Wheat, barley, oats, millet, sugar beets, and most forage legumes and grasses were developed in the region encompassing the Middle East, North Africa, and southern Europe. Corn, potatoes, peanuts, sunflowers, and tobacco were cultivated in the Americas. Soybeans, onions, lettuce, and peas were first grown in China. Sugar cane and rice, most citrus fruits, and bananas came from southern Asia.

Crops spread evenly throughout the ancient world. Corn and potatoes were grown in both North and South America long before Europeans arrived, and wheat and barley were distributed throughout the Near East well before the time of the pharaohs of Egypt. Centuries later, as sailing ships spanned the globe, favorite crops were distributed worldwide by colonists who carried and planted seeds from their homelands in the lands where they settled. From the 16th through the 19th centuries, the opening of vast new lands through conquests, as well as the need to provide slaves and other large concentrations of workers with a ready supply of cheap food, stimulated the movement and cultivation of crops on a worldwide scale. In the 20th century, the decline of suitable new croplands and the dramatic increase in world population have given a new focus and a sense of urgency to the exploration and development of food crops.

Modern crop farming varies widely in its scope, ranging from intensively managed small plots to commercial farms covering thousands of acres. Successful crop farmers must be expert at selecting the kinds and varieties of plants that are adapted to their soils and climate. They must be skilled in preparing soil and in planting, growing, protecting, harvesting, and storing crops. They must be able to control weeds, insects, and diseases, and they need good marketing skills to gain reasonable returns from their crops.

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New applications of technologies in the 1990s are increasing crop production. Precision farming, also known as prescription farming, site specific farming, or variable rate farming, utilizes global positioning systems (GPS) and geographic information systems (GIS) in the satellite collection and transmission of data as farmers plant, fertilize, and harvest their crops.

Combines and other harvesting machines equipped with electronic scales, which are linked to a GPS, measure yield as a crop is being harvested. A computerized yield map, which locates to within one meter (one yard) those spots in a field where the yield is highest and lowest, is produced. The next time that field is planted and fertilized, the farmer adjusts seeding and fertilizer application rates according to information on the yield map. This increases crop production while reducing the use of both fertilizers and fuel.

GPS also help farmers comply with environmental regulations that require a buffer free of pesticides between areas where they are applied to crops and nearby streams. Pesticide spraying equipment can be preprogrammed to turn off when it reaches the buffer zones.

Biotechnology is also increasing agricultural productivity. Farmers in Georgia are producing a new, genetically engineered oilseed crop that grows from canola, an oilseed producing plant, to yield lauric oil, which comes naturally from coconuts and palm kernels. Scientists developed the new seed by transplanting a single gene from a laurel tree into canola plants. New hybrid (offspring from dissimilar parents) corn seed recently developed to resist the corn borer, an insect poisonous to that crop, is now under cultivation. Improved varieties of barley with new disease resistant genes represent another application of biotechnology that reduces the use of pesticides while increasing yield.

II

Grain Crops

The most important food-energy source for three-fourths of the world population is grains. Most grains are members of the grass family (see Grasses) that are grown for their large edible seeds. Chief among these are wheat, rice, corn (maize), barley, oats, rye, sorghum, and millet. All are widely used as food for humans, both directly and in processed forms. Corn, barley, oats, and sorghum also serve as livestock and poultry feeds; stalks and straw from these crops are important sources of fodder (feed) and bedding for livestock. Grains are among the oldest crops, with their cultivation dating from about 10,000 years ago.

Wheat, barley, oats, and rye are grown throughout much of the Temperate Zone world, most commonly in areas with moderate to low annual rainfall (25 to 76 cm/10 to 30 in), where they are more productive than crops that require more water. Higher rainfall, irrigation, and fertilization, however, boost the yields of these cereal grains. Rice is primarily a tropical or subtropical cereal, although Chinese and Japanese breeders have developed short-season strains adapted to temperate areas. Most rice is grown in water or in paddies with ample water supplies. Upland, or dryland, rice is grown in limited areas.

Sorghum historically has been a tropical grain, grown for food in Africa and Asia. In the past half century its use has spread so widely that it has become an important livestock feed in dryland (arid) areas such as the southwestern United States. Corn originated in subtropical climates, but is now grown predominantly in temperate climates that have rainfall of more than 63 cm (more than 25 in) per year. Rapid expansion of irrigation systems has made possible the extension of corn acreage into drier areas in the central and western United States.

Grain crops are well adapted to mechanization. In the temperate zones most grain production is on large farms, where machines till, plant, and harvest (see Agricultural Machinery). This is less true in the Tropics and in locations where terrain is too rough for machinery. In these areas grains are grown in small plantings. Here much of the planting, harvesting, and threshing continues to be done by hand or with primitive equipment.

The development in the 1960s of improved grain-crop varieties with higher yields, stronger pest resistance, and greater response to fertilizers has improved productivity throughout much of the world. In many areas of the Tropics, the new developments triggered the so-called green revolution, a dramatic increase in grain production. More work was needed, however, to adapt superior varieties to local conditions and to solve human problems associated with the distribution of their benefits. The energy shortage that began in 1973 led to a shortage of oil-based chemical fertilizers and of fuel to run irrigation pumps, which also placed constraints on further gains from the green revolution.

III

Forage Crops

Forage-crop farming serves as the basis for much of the world’s livestock industries. Forage crops are mowed, dried, and stored as hay; chopped and stored wet as silage; or fed directly to cattle as pasture or as freshly chopped forage. In tropical and subtropical regions, most livestock consume forages as pasture. In temperate zones, forages are commonly stored as hay or silage for winter use.

Common legume forages of the temperate zones include alfalfa; red, white, and alsike clovers; and birdsfoot trefoil. Popular grasses include timothy, orchard grass (cocksfoot), smooth bromegrass, tall fescue, and bluegrass. Forage-crop farmers normally grow one or more legumes in association with a grass. Bacteria in the root nodules of the legumes convert atmospheric nitrogen (see Nitrogen Fixation) into forms available to these plants and enrich the soil for the grasses as well, thereby reducing the need for fertilizer and increasing the yields and the quality of the forage.

IV

Fruit Crops

The temperate, subtropical, and tropical regions of the world all grow important fruit crops. Apples, pears, peaches, plums, nectarines, and cherries are the major temperate fruits. Oranges, lemons, limes, tangerines, olives, and figs are subtropical crops. The leading tropical fruits include bananas, avocados, mangoes, dates, pineapples, and papayas. Small fruits and berries are also widely grown, particularly in temperate regions. Most important are grapes, strawberries, blackberries, raspberries, blueberries, and cranberries.

Nearly all commercial fruit trees are propagated vegetatively—that is, without the use of seed (see Plant Propagation). Growers take cuttings or buds from the varieties that have desirable fruit qualities and graft these onto seedling rootstocks of the strains selected for adaptation to local soil and climatic conditions and for resistance to root-destroying diseases and insects. In recent years many fruit growers have shifted to the use of “dwarfing” rootstocks to reduce tree size. This procedure makes fruit harvesting easier and less costly, and it permits increased plant density and high yields per unit area of land.

Cultural practices differ for each fruit species, depending on the type of soil, climate, and fertilizer it needs. Close control of insects and diseases is essential in commercial plantings to produce high-quality fruit and profitable yields. Commercial growers began to rely heavily on chemical sprays in the 1960s, but after two decades of accelerating pest resistance and environmental damage, modern growers have shifted toward biological controls and careful monitoring of pest populations, spraying chemicals only at those times when the controls would be most effective (see Pest Control).

Most fruit crops are harvested by hand, but commercial fruit growers in the United States and Europe are mechanizing where practical in order to reduce labor and other costs. By the 1980s, mechanical harvesters picked many grape and cherry crops in the United States, and machines were adapted for use on apple and berry crops.

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