Crop Farming

I

Introduction

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

Modern crops evolved around their ancient centres of origin. Wheat, barley, oats, millet, sugar beet, 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. Soya beans, onions, lettuce, and peas were first grown in China. Sugar cane and rice, most citrus fruits, and bananas came from southern Asia.

Crops spread widely even in the ancient world. Corn and potatoes were grown throughout North and South America long before the Europeans arrived; and early wheat and barley were distributed throughout the Near East well before the time of the pharaohs. Later, as sailing ships spanned the globe, favoured crops became distributed worldwide by colonists, who carried seeds from their homelands and added them to the crops of the new land. Between the 16th and 19th centuries, the opening up 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 gave 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 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 also be able to control weeds, insects, and diseases, and have marketing skills to enable them to gain reasonable returns from their crops.

II

Grain Crops

The most important food-energy source for three-quarters of the world's population is grain. Most grains are members of the grass family, 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. Grains are among the oldest crops, with their cultivation dating back about 10,000 years.

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 mm/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 growers have developed short-season strains adapted to temperate areas. Most rice is grown in water or in paddy fields with ample water supplies. Upland, or dryland, rice is grown in limited areas. Historically, sorghum 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 areas such as the south-western United States. Corn originated in subtropical climates, but is now grown predominantly in temperate areas that have rainfall of more than 63 mm (25 in) per year.

Grain crops are well adapted to mechanization. In the temperate zones most grain production is on large farms, where agricultural machinery perform the tilling, planting, and harvesting. This is less true in the tropics and in locations where the terrain is too rough for machinery. In these areas grain is grown on small farms, and 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 lack 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 is concerned with the production of food for 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 by a process called 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 seeds (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 towards biological pest control and careful monitoring of pest populations, spraying chemicals only at those times when the controls would be most effective.

Most fruit crops are harvested by hand, but commercial fruit growers in Europe and the United States use mechanization where practical in order to reduce labour and other costs.