Agriculture is the process of producing food, feed, fiber and other desired products by the cultivation of certain plants and the raising of domesticated animals (livestock). The practice of agriculture is also known as farming, while scientists, inventors and others devoted to improving farming methods and implements are also said to be engaged in agriculture.
More people in the world are involved in agriculture as their primary economic activity than in any other, yet it only accounts for four percent of the world's GDP.
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Agriculture can refer to subsistence agriculture, the production of enough food to meet just the needs of the farmer/agriculturalist and his/her family. It may also refer to industrial agriculture, (often refered to as factory farming) long prevalent in "developed" nations and increasingly so elsewhere, which consists of obtaining financial income from the cultivation of land to yield produce, the commercial raising of animals (animal husbandry), or both.
Agriculture is also short for the study of the practice of agriculture—more formally known as agricultural science.
Increasingly, in addition to food for humans and animal feeds, agriculture produces goods such as cut flowers, ornamental and nursery plants, timber or lumber, fertilizers, animal hides, leather, industrial chemicals (starch, sugar, ethanol, alcohols and plastics), fibers (cotton, wool, hemp, and flax), fuels (methane from biomass, biodiesel) and both legal and illegal drugs (biopharmaceuticals, tobacco, marijuana, opium, cocaine). Genetically engineered plants and animals produce specialty drugs.
In the Western world, the use of gene manipulation, better management of soil nutrients, and improved weed control have greatly increased yields per unit area. At the same time, the use of mechanization has decreased labour requirements. The developing world generally produces lower yields, having less of the latest science, capital, and technology base.
Modern agriculture depends heavily on engineering and technology and on the biological and physical sciences. Irrigation, drainage, conservation and sanitary engineering, each of which is important in successful farming, are some of the fields requiring the specialized knowledge of agricultural engineers.
Agricultural chemistry deals with other vital farming concerns, such as the application of fertilizer, insecticides (see Pest control), and fungicides, soil makeup, analysis of agricultural products, and nutritional needs of farm animals.
Plant breeding and genetics contribute immeasurably to farm productivity. Genetics has also made a science of livestock breeding. Hydroponics, a method of soilless gardening in which plants are grown in chemical nutrient solutions, may help meet the need for greater food production as the world's population increases.
The packing, processing, and marketing of agricultural products are closely related activities also influenced by science. Methods of quick-freezing and dehydration have increased the markets for farm products (see Food preservation; Meat packing industry).
Mechanization, the outstanding characteristic of late 19th and 20th century agriculture, has eased much of the backbreaking toil of the farmer. More significantly, mechanization has enormously increased farm efficiency and productivity (see Agricultural machinery). Animals, including horses, mules, oxen, camels, llamas, alpacas, and dogs; however, are still used to cultivate fields, harvest crops and transport farm products to markets in many parts of the world.
Airplanes, helicopters, trucks and tractors are used in agriculture for seeding, spraying operations for insect and disease control, transporting perishable products, and fighting forest fires. Radio and television disseminate vital weather reports and other information such as market reports that concern farmers. Computers have become an essential tool for farm management.
According to the National Academy of Engineering in the US, agricultural mechanization is one of the 20 greatest engineering achievements of the 20th century. Early in the century, it took one American farmer to produce food for 2.5 people, where today, due to engineering technology (also, plant breeding and agrichemicals), a single farmer can feed over 130 people [1]. This comes at a cost, however, of large amounts of energy input, from unsustainable, mostly fossil fuel, sources.
Animal husbandry means breeding and raising animals for meat or to harvest animal products (like milk, eggs, or wool) on a continual basis.
In recent years some aspects of industrial intensive agriculture have been the subject of increasing discussion. The widening sphere of influence held by large seed and chemical companies, meat packers and food processors has been a source of concern both within the farming community and for the general public. There has been increased activity of some people against some farming practices, raising chickens for food being one example. Another issue is the type of feed-stock given to some animals that can cause Bovine Spongiform Encephalopathy in cattle.
The patent protection given to companies that develop new types of seed using genetic engineering has allowed seed to be licensed to farmers in much the same way that computer software is licensed to users. This has changed the balance of power in favor of the seed companies, allowing them to dictate terms and conditions previously unheard of. Some argue these companies are guilty of biopiracy.
Soil conservation and nutrient management have been important concerns since the 1950s, with the best farmers taking a stewardship role with the land they operate. However, increasing contamination of waterways and wetlands by nutrients like nitrogen and phosphorus are of concern in many countries.
Increasing consumer awareness of agricultural issues has led to the rise of community-supported agriculture, local food movement, slow food, and commercial organic farming, though these yet remain fledgling industries.
Archaeobotanists have traced the selection and cultivation of specific food plant characteristics, such as a semi-tough rachis and larger seeds, to just after the Younger Dryas (about 9,500 BC) in the early Holocene in the Levant region of the Fertile Crescent. Limited anthropological and archaeological evidence both indicate a grain-grinding culture farming along the Nile in the 10th millennium BC using the world's earliest known type of sickle blades. There is even earlier evidence for conscious cultivation and seasonal harvest: grains of rye with domestic traits have been recovered from Epi-Palaeolithic (10,000+ BC) contexts at Abu Hureyra in Syria, but this appears to be a localised phenomenon resulting from cultivation of stands of wild rye, rather than a definitive step towards domestication. It is not until ca. 8,500 BC, in middle-Eastern cultures referred to as Pre-Pottery Neolithic B (PPNB), where there is the first definite evidence for the emergence of a widespread subsistence economy that was dependent on domesticated plants and animals. In these contexts lie the origins of the eight so-called founder crops of agriculture: firstly emmer wheat, einkorn wheat, then hulled barley, pea, lentil, bitter vetch, chick pea and flax. These eight crops occur more or less simultaneously on PPNB sites in this region, although the consensus is that wheat was the first to be sown and harvested on a significant scale. There are many sites that date to between ca. 8,500 BC and 7,500 BC where the systematic farming of these crops contributed the major part of the inhabitants' diet. From the Fertile Crescent agriculture spread eastwards to Central Asia and westwards into Cyprus, Anatolia and, by 7,000 BC, Greece. Farming, principally of emmer and einkorn, reached northwestern Europe via southeastern and central Europe by ca. 4,800 BC (see, among others, Price, D. [ed.] 2000. Europe's First Farmers. Cambrige Universty Press; Harris, D. [ed.] 1996 The Origins and Spread of Agriculture in Eurasia. UCL Press).
The reasons for the earliest introduction of farming may have included climate change, but possibly there were also social reasons (e.g. accumulation of food surplus for competitive gift-giving). Most certainly there was a gradual transition from hunter-gatherer to agricultural economies after a lengthy period when some crops were deliberately planted and other foods were gathered from the wild. Although localised climate change is the favoured explanation for the origins of agriculture in the Levant, the fact that farming was 'invented' at least three times, possibly more, suggests that social reasons may have been instrumental. In addition to emergence of farming in the Fertile Crescent, agriculture appeared by at least 6,800 BC in East Asia (rice) and, later, in Central and South America (maize, squash). Small scale agriculture also likely arose independently in early Neolithic contexts in India (rice) and Southeast Asia (taro).
Full dependency on domestic crops and animals (i.e. when wild resources contributed a nutritionally insignificant component to the diet) was not until the Bronze Age. If the operative definition of agriculture includes large scale intensive cultivation of land, mono-cropping, organised irrigation, and use of a specialized labour force, the title "inventors of agriculture" would fall to the Sumerians, starting ca. 5,500 BC. Intensive farming allows a much greater density of population than can be supported by hunting and gathering and allows for the accumulation of excess product to keep for winter use or to sell for profit. The ability of farmers to feed large numbers of people whose activities have nothing to do with material production was the crucial factor in the rise of standing armies. The agriculturalism of the Sumerians allowed them to embark on an unprecedented territorial expansion, making them the first empire builders. Not long after, the Egyptians, powered by effective farming of the Nile valley, achieved a population density from which enough warriors could be drawn for a territorial expansion more than tripling the Sumerian empire in area.
The invention of a three field system of crop rotation during in the Middle Ages vastly improved agricultural efficiency.
After 1492 the world's agricultural patterns were shuffled in the widespread exchange of plants and animals known as the Columbian Exchange. Crops and animals that were previously only known in the Old World were now transplanted to the New and vice versa. Perhaps most notably, the tomato became a favorite in European cuisine, while certain wheat strains quickly took to western hemisphere soils and became a dietary staple even for native North, Central and South Americans.
By the early 1800s agricultural practices, particularly careful selection of hardy strains and cultivars, had so improved that yield per land unit was many times that seen in the Middle Ages and before, especially in the largely virgin lands of North and South America. With the rapid rise of mechanization in the 20th century, especially in the form of the tractor, the demanding tasks of sowing, harvesting and threshing could be performed with a speed and on a scale barely imaginable before. These advances have led to efficiencies enabling certain modern farms in the United States, Argentina, Israel, Germany and a few other nations to output volumes of high quality produce per land unit at what may be the practical limit.
In millions of metric tons, based on FAO estimates[2]:
Domestication of plants is done in order to increase yield, improve disease resistance and drought tolerance, ease harvest and to improve the taste and nutritional value and many other characteristics. Centuries of careful selection and breeding have had enormous effects on the characteristics of crop plants. Plant breeders use greenhouses and other techniques to get as many as three generations of plants per year so that they can make improvements all the more quickly.
Plant selection and breeding in the 1920s and '30s improved pasture (grasses and clover) in New Zealand. Extensive radiation mutagenesis efforts (i.e. primitive genetic engineering) during the 1950s produced the modern commercial varieties of grains such as wheat, corn and barley.
For example, average yields of corn (maize) in the USA have increased from around 2.5 tons per hectare (40 bushels per acre) in 1900 to about 9.4 t/ha (150 bushels per acre) in 2001, primarily due to improvements in genetics. Similarly, worldwide average wheat yields have increased from less than 1 t/ha in 1900 to more than 2.5 t/ha in 1990. South American average wheat yields are around 2 t/ha, African under 1 t/ha, Egypt and Arabia up to 3.5 to 4 t/ha with irrigation. In contrast, the average wheat yield in countries such as France is over 8 t/ha. Higher yields are due to improvements in genetics, as well as use of intensive farming techniques (use of fertilizers, chemical pest control, growth control to avoid lodging).
[Conversion note: 1 bushel of wheat = 60 pounds (lb) ≈ 27.215 kg. 1 bushel of corn = 56 pounds ≈ 25.401 kg]
Very recently, genetic engineering has begun to be employed in some parts of the world to speed up the selection and breeding process. The most widely used modification is a herbicide resistance gene that allows plants to tolerate exposure to glyphosate, which is used to control weeds in the crop. A less frequently used but more controversial modification causes the plant to produce a toxin to reduce damage from insects (c.f. Starlink).
There are specialty producers who raise less common types of livestock or plants.
Aquaculture, the farming of fish, shrimp, and algae, is closely associated with agriculture.
Apiculture, the culture of bees, traditionally for honey—increasingly for crop pollination.
See also : botany, List of domesticated plants, List of vegetables, List of herbs, List of fruit
Agricultural policy focuses on the goals and methods of agricultural production. At the policy level, common goals of agriculture include:
Agricultural machinery is one of the most revolutionary and impactful applications of modern technology. Given the truly elemental human need for food, agriculture has been an essential human activity almost from the beginning, and it has often driven the development of technology and machines. Over the last 250 years, advances in farm equipment have dramatically changed the way people are employed and produce their food worldwide.
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Doubtless, the first man to turn from the hunting and gathering lifestyle to farming did so by using his bare hands, and perhaps some sticks or stones. Tools such as knives, scythes, and wooden plows were eventually developed, and dominated agriculture for thousands of years. During this time, almost everyone worked in agriculture, because each family could barely raise enough food for themselves with the limited technology of the day.
With the coming of the Industrial Revolution and the development of more complicated machines, farming methods took a great leap forward. Instead of harvesting grain by hand with a sharp blade, wheeled machines cut a continuous swath. Instead of threshing the grain by beating it with sticks, threshing machines separated the seeds from the heads and stalks.
These machines required a lot of power, which was originally supplied by horses or other domesticated animals. With the invention of steam power came the steam-powered tractor, a multipurpose, mobile energy source that was the ground-crawling cousin to the steam locomotive. Agricultural steam engines took over the heavy pulling work of horses, and were also equipped with a pulley that could power stationary machines via the use of a long belt. The steam-powered behemoths could provide a tremendous amount of power, both because of their size and their low gear ratios. Their slow speed led farmers to comment that tractors had two speeds: "slow, and damn slow."
Gasoline, and later diesel engines became the main source of power for the next generation of tractors. These engines also contributed to the development of the self-propelled, combined harvester and thresher, or combine for short. Instead of cutting the grain stalks and transporting them to a stationary threshing machine, these combines cut, threshed, and separated the grain while moving continuously through the field.
Combines may have taken the harvesting job away from tractors, but tractors still do the majority of work on a modern farm. They are used to pull implements—machines that till the ground, plant seed, or perform a number of other tasks.
Tillage implements prepare the soil for planting by loosening the soil and killing weeds or competing plants. The best-known is the plow, the ancient implement that was upgraded in 1838 by a man named John Deere. Plows are actually used less frequently in the U.S. today, with offset disks used instead to turn over the soil and chisels used to gain the depth needed to retain moisture.
The most common type of seeder is called a planter and spaces seeds out equally in long rows, which are usually 2 to 3 feet apart. Some crops are planted by drills, which put out much more seed in rows less than a foot apart, blanketing the field with crops. Transplanters fully or partially automate the task of transplanting seedlings to the field. With the widespread use of plastic mulch, plastic mulch layers, transplanters, and seeders lay down long rows of plastic, and plant through them automatically.
After planting, other implements can be used to cultivate weeds from between rows, or to spread fertilizer and pesticides. Hay balers can be used to tightly package grass or alfalfa into a storable form for the winter months.
When was the horse collar invented?
Modern irrigation also relies on a great deal of machinery. A variety of engines, pumps and other specialized gear is used to provide water quickly and in high volumes to large areas of land. Similar types of equipment can be used to deliver fertilizers and pesticides.
And, besides the tractor, a variety of vehicles have been adapted for use in various aspects of farming, including trucks, airplanes, and helicopters, for everything from transporting crops and making equipment mobile, to aerial spraying and livestock herd management.
The basic technology of agricultural machines has changed little in the last century. Though modern harvesters and planters may do a better job or be slightly tweaked from their predecessors, the US$250,000 combine of today still cuts, threshes, and separates grain in essentially the same way it has always been done. However, technology is changing the way that humans operate the machines, as computer monitoring systems, GPS locators, and self-steer programs allow the most advanced tractors and implements to be more precise and less wasteful in the use of fuel, seed, or fertilizer. In the foreseeable future, some agricultural machines will be capable of driving themselves, using GPS maps and electronic sensors. Even more esoteric are the new areas of nanotechnology and genetic engineering, where submicroscopic devices and biological processes, respectively, are being used as machines to perform agricultural tasks in unusual new ways.
Agriculture may be one of the oldest professions, but the development and use of machinery has made the job title of farmer a rarity. Instead of every person having to work to provide food for themselves, less than 2% of the U.S. population today works in agriculture, yet that 2% provides considerably more food than the other 98% can eat. It is estimated that at the turn of the 20th century, one farmer in the U.S. could feed 25 people, where today, that ratio is 1:130. With continuing advances in agricultural machinery, the role of the farmer will become increasingly specialized, and rare.
Farm equipment is any kind of machinery used on a farm to help with farming. The best-known example of this kind of equipment is the tractor.
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A tractor (from Latin trahere "to pull") is a device intended for drawing, towing or pulling something which cannot propel itself and, often, powering it too. Most commonly the word is used to describe a vehicle intended for such a task on some other vehicle or object.
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The most common use of the term tractor is for the vehicles used on farms. The farm tractor is used for pulling agricultural machinery or trailers, for ploughing, harrowing and similar tasks. The classic farm tractor is a simple open vehicle with two very large driving wheels on an axle below and slightly behind a single seat (the seat and steering wheel consequently are in the center) and the engine in front of the driver with two steerable wheels below the engine compartment. This basic design has remained unchanged for a number of years, but now enclosed cabs are available for many models of farm tractor.
There are usually four foot-pedals, for the operator, on the floor of a tractor. The pedal on the left is the clutch. The operator presses on this pedal to disengage the transmission for either shifting gears or stopping the tractor. Two of the pedals on the right are the brakes. The left brake pedal stops the left rear wheel and the right brake pedal does the same with the right side. This independent left and right wheel braking augments the steering of the tractor when only the two rear wheels are driven. This is usually done when it is necessary to make a tight turn. The split brake pedal is also used in mud or soft dirt to control a tire that spins due to loss of traction. The operator presses both pedals together to stop the tractor. For tractors with additonal front-wheel drive, this operation often engages the 4-wheel locking differential to help stop the tractor when travelling at road speeds.
The pedal furthest to the right is the foot throttle. Unlike those in automobiles, it can also be controlled from a hand-operated lever ("hand throttle"). This helps provide a constant speed in field work. It also helps provide continuous power for stationary tractors that are operating an implement by shaft or belt. The foot throttle gives the operator more automobile-like control over the speed of the tractor for road work. When travelling on the road in the UK, it is mandatory to use the foot pedal to control engine speed.
Most farm tractors use a manual transmission. They have several gears which generally provide a range of speeds from less than a mile per hour up to about 25 miles per hour. Compared to other vehicles the tractor is quite slow. Slower speeds are necessary for most operations that are performed with a tractor. These slower speeds help give the farmer a larger degree of control in certain situations—such as field work. Older tractors generally require that the operator press in the clutch to shift the gears but many modern tractors can shift between certain gears without the need to depress the clutch. The former was a limitation of straight-cut gears in the gearbox, the latter an advance so that the operator can have more control over working speed than just the throttle.
Modern farm tractors range in size from 18 to 500 horsepower (15 to 400 kW). Tractors can be generally classified as two wheel drive, two wheel drive with front wheel assist, or four wheel drive (with articulated steering). Variations of the classic style include the diminutive lawn tractors and their more capable and ruggedly constructed cousins garden tractors, which tend to range from 10 to 25 horsepower and are used for smaller farm tasks, mowing grass, and landscaping. The size - especially with modern tractors - and the slower speeds are reasons motorists are urged to use caution when encountering a tractor on the roads.
Modern tractors have roll over protection systems (ROPS) to prevent an operator from being crushed in the event of a rollover. This is especially important in open-air tractors. In open-air tractors the ROPS is a steel beam that extends above the operator's seat. For tractors with operator cabs, the ROPS is part of the frame of the cab. Before ROPS were required many farmers died when their tractors rolled over on top of them. Row-crop tractors, before ROPS, were particularly dangerous because of their 'tricycle' design with the two front wheels spaced close together and pointed inward toward the ground. Many farmers were killed by rollovers while operating tractors along steep slopes. ROPS were first required by legislation in New Zealand in the 1960s.
Most tractors have a means to transfer the engine's power to another machine such as a baler or mower. Early tractors used belts wrapped around pulleys to power stationary equipment. Modern tractors use a power take-off shaft (PTO) to provide rotary power to machinery that may be stationary or pulled. Almost all modern tractors can also provide hydraulic and electrical power.
Farm implements can be attached to the rear of the tractor by either a drawbar or by a three-point hitch. The three-point hitch was invented by Harry Ferguson and has been a standard since the 1960s. Equipment attached to the three-point hitch can be raised or lowered hydraulically with a control lever. The equipment attached to the three-point hitch is usually completely supported by the tractor.
The durability and engine power of tractors made them very suitable for engineering tasks. Tractors can be attached with different engineering tools such as dozer blade, bucket, hoe, ripper and so on. The most common attachments for the front of a tractor are dozer blade or a bucket. When attached with engineering tools the tractor is called an engineering vehicle.
A bulldozer is a tracked-type tractor attached with blade in the front and a rope-winch behind. Bulldozers are very powerful tractors and have excellent ground-hold, as their main tasks are to push or drag things.
Bulldozers have been further modified over time to evolve into new machines which are capable of working in ways that the original bulldozer can not. One example is that loader tractors were created by removing the blade and substituting a large volume bucket and hydraulic arms which can raise and lower the bucket, thus making it useful for scooping up earth, rock and similar loose material to load it into trucks.
A front-loader or loader is a tractor with an engineering tool which consists of two hydraulic powered arms on either side of the front engine compartment and a tilting implement. This is usually a wide open box called a bucket but other common attachments are a pallet fork and a bale grappler.
Other modifications to the original bulldozer include the reduction in size of the machine to permit it to operate in small work areas where movement is limited. There are also tiny wheeled loaders, officially called Skid-steer loaders but nicknamed "Bobcat" after the original manufacturer, which are particularly suited for small excavation projects in confined areas.
The most common variation of the classic farm tractor is the loader-backhoe, also called a backhoe-loader. As the name implies, it has a loader assembly on the front and a backhoe on the back. When both the loader and the backhoe are permanently attached it is almost never called a tractor, not generally used for towing and usually does not have a PTO. When the backhoe is permanently attached, the machine usually has a seat that can swivel to the rear to face the hoe controls. Removable backhoe attachments almost always have a separate seat on the attachment itself.
Backhoe-loaders are very common and can be used for a wide variety of tasks: construction, small demolitions, light transportation of building materials, powering building equipment, digging holes, breaking asphalt and paving roads. Some buckets have a retractable bottom, enabling them to empty their load more quickly and efficiently. Retractable-bottom buckets are also often used for grading and scratching off sand. The front assembly may be a removable attachment or permanently mounted. Often the bucket can be replaced with other devices or tools.
Their relatively small frame and precise control make backhoe-loaders very useful and common in urban engineering projects such as construction and repairs in areas too small for larger equipment. Their versatility and compact size makes them one of the most popular urban construction vehicles.
The term tractor is applied also to:
In aircraft, a tractor configuration refers to the propellers being in front of the fuselage or wing. Conversely, if to the rear, it is a called a pusher configuration.
NASA and other space Agencies use very large tractors to ferry launch vehicles like booster rockets and space shuttles from their hangars to (and in rare cases, from) the launchpad .
Space technology has also trickled back down to agriculture in the form of GPS devices, and robust on-board computers installed as optional features on farm tractors. The spin-offs from the space race have actually facilitated automation in plowing and the use of driverless drone tractors that work in tandem with manned tractors on large corporate-scale farms.
A tractor is also the part of a computer printer that pulls paper into the device or pushes it along. This usually takes the form of a toothed gear that meshes with holes punched near the edge of the paper, or a belt or wheel with rubber or other high-friction surface that makes contact with the paper.
The Chisel Plow is common tool to get deep tillage with limited soil disruption. The main function of this plow it to loosen and airate the soils while leaving crop residue at the top of the soil. This plow can be used to reduce the effects of compaction and to help break up plowpan and hardpan. Unlike many other plows the chisel will not invert or turn the soil. This characteristic has made it a useful addition to no-till and limited-tillage farming practices which attempt to maximize the erosion prevention benefits of keeping organic mater and farming residues present on the soil surface through the year. Because of these attributes, the use of a chisel plow is considered by some to be more sustainable than other types of plow, such as the moldboard plow.
The chisel plow is typically set to run up to a depth of eight to
twelve inches however some models may run much deeper. Each of the
individual plows, or shanks, are typically set from nine inches to
twelve inches apart. Such a plow can encounter significant soil drag,
consequently a tractor
of sufficient power and good traction is required. When planning to
plow with a chisel plow it is important to bear in mind that 10 to 15
horsepower (7 to 11 kW) per shank will be required.
This article is about the agricultural tool. For other meaning, see Harrow (disambiguation)
In agriculture, a harrow is an implement for cultivating the surface of the soil, in this way it is distinct in its effect from the plough, which is used for deeper cultivation. Harrows were originally horse-drawn. In modern practice they are almost always tractor-mounted implements, drawn after the tractor.
Harrowing is often carried out on fields to follow the rough finish left by ploughing operations. The purpose of this harrowing is generally to break up clods and lumps of soil and to provide a finer finish, a tilth, that is suitable for seeding and planting operations. Harrowing may also be used in farming to remove weeds and to cover seed after sowing.
In modern sports grounds maintenance a light chain harrowing is often used to level off the ground, after heavy use, to remove and smooth out boot marks and indentations.
Harrows may be of several types and weights, depending on the intended purpose. They almost always consist of a rigid frame to which are attached disks, teeth, linked chains or other means of cultivation. In the colder climates the commonest types are the disk harrow and the chain harrow but in New Zealand and Australian dairy areas the tine harrow is common. Chain harrows are often used for lighter work such levelling the tilth or covering seed, while disk harrows are typically used for heavy work, such as following ploughing to break up the sod. In addition, there are various types of 'power harrow', in which the cultivators are power-driven from the tractor rather than depending on its forward motion.
A drag is a heavy harrow.
The following text is taken from the Household Cyclopedia of 1881:
The plough (American spelling: plow) is a tool used in farming for initial cultivation of soil in preparation for sowing seed or planting.
The plough can be regarded as a development of the pick, or of the spade. Ploughs were initially pulled by humans, later by oxen, and later still in some countries, by horses. Modern ploughs are, in industrialized countries, powered by tractors.
Ploughing has several beneficial effects. The major reason for ploughing is to turn over the upper layer of the soil. This may also incorporate the residue from the previous crop into the soil. Ploughing reduces the prevalence of weeds in the fields, and makes the soil more porous, easing later planting.
The early German word before sound-shift is plug and in Old Prussian plugis. After the German sound shift (p = pf) it became the modern German word Pflug.
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When agriculture was first developed, simple hand held digging sticks or hoes would have been used in highly fertile areas, such as the banks of the Nile where the annual flood rejuvenates the soil, to create furrows wherein seeds could be sown. In order to regularly grow crops in less fertile areas, the soil must be turned to bring nutrients to the surface.
The domestication of oxen in Mesopotamia, perhaps as early as the 6th millennium BC, provided mankind with the pulling power necessary to develop the plough. The very earliest ploughs were simple scratch-ploughs and consisted of a frame holding a vertical wooden stick that was dragged through the topsoil.
These were much later developed into mouldboard ploughs (American spelling: moldboard) that turned the soil in one run across the field, depositing the weeds and undecomposed remains of the previous crop under the soil and raising the rain-percolated nutrients back to the surface. This plough also allowed for ploughing while the ground was wet. The water was drained due to channels formed under the overturned earth. This important innovation, introduced into Europe around 600AD, allowed the heavy northern soils to be worked.
The mouldboard, carried below the frame, is tipped with a share, an asymmetric arrow-shaped device designed to slice through the ground horizontally as it moves forward. It also has a coulter, a sharpened blade or disc, attached to the frame of the plough to cut down through the ground, ahead of the share, and also to cut deepset and tough roots. A runner extending from behind the share to the rear of the plough controls the direction of the plough, because it is held against the bottom land-side corner of the new furrow being formed. The holding force is the weight of the sod, as it is raised and rotated, on the curved surface of the moldboard. Because of this runner, the mouldboard plough is harder to turn around than the scratch plough, and its introduction brought about a change in the shape of fields -- from mostly square fields into longer rectangular "strips" (hence the introduction of the furlong).
The first commercially successful iron plough was the Rotherham plough, developed by Joseph Foljambe in Rotherham, England, in 1730. It was durable and light, and was engineered after the mathematical principles of James Small, who designed a mouldboard that would cut, lift and turn over the strip of earth. (It should be noted that all the major components of the Rotherham plough had been well known in China for millenia, and diffusion of technology from China, probably by the Dutch, is highly likely).
Steel ploughs were developed during the Industrial Revolution and were lighter and more durable than ploughs made of iron or wood. The cast-steel plow was developed by U.S. blacksmith John Deere in the 1830s. By this time the hitch, to the draught animals, was adjustable so that the wheel at the front was held onto the ground. The first steel ploughs were walking ploughs, having two handles held by the ploughman to provide a degree of control over the depth and location of the furrow behind the draughting force. The ploughman often was also controlling the draught animal(s). Riding ploughs with wheels and a seat for the operator came later, and often had more than one share.
A single draught horse can normally pull a single-furrow plough in clean, light, soil but in heavier soils two animals are needed, one walking on the land and one in the furrow. For ploughs with two or more furrows, one or more horses have to walk on the loose, ploughed, sod -- and that makes hard going for them. It is usual to rest such animals every half hour for about ten minutes.
The Stump-Jump plough is an Australian invention of the 1870s, designed to cope with the breaking up of new farming land, that contains many tree stumps and rocks that would be very expensive to remove from paddocks. The plough uses a moveable weight to hold the ploughshare in position. When a tree stump or other obstruction such as a rock is encountered, the ploughshare is thrown upwards, clear of the obstacle, to avoid breaking the harness or linkage of the whole plough; ploughing can be continued when the weight is returned to the earth after the obstacle is passed.
A simpler system, developed later, uses a concave disk (or a pair of them) set at a large angle to the direction of progress, that uses the concave shape to hold the disk into the soil -- unless something hard strikes the circumference of the disk, causing it to roll up and over the obstruction. As the arrangement is dragged forward, the sharp edge of the disk cuts the soil, and the concave surface of the rotating disk lifts and throws the soil to the side. It doesn't make as good a job as the mouldboard plough (but this is not considered a disadvantage, because it helps fight the wind erosion), but it does lift and break up the soil.
Traditional ploughs can only turn the soil over in one direction, as dictated by the shape of the mouldboard. The resulting method of traversing an entire field leads to the ridge and furrow effect seen in some ancient fields.
Modern ploughs are reversible, having 2 sets of mouldboards: whilst one is working the land, the other is carried upside-down in the air. During the cultivation process, hydraulics are used to turn over the entire implement at each end of the field so that the second set of moulboards can be used. The field can then be traversed in such a way as to keep the land level, avoiding ridges and furrows.
The modern reversible plough is mounted on a tractor via a three-point hitch. These commonly have sets of 5 mouldboards, but semi-mounted ploughs, the lifting of which are supplemented by a wheel about half-way along its length, can have as many as 18. The hydraulic system of the tractor is used to lift and reverse the implement, as well as adjust furrow width and depth. The ploughman still has to set the draughting linkage from the tractor so that the plough is carried at the proper angle in the soil. This angle and depth can be controlled automatically by modern tractors.
On modern ploughs and some older ploughs, the mouldboard is separate from the share and runner, allowing these parts to be replaced without replacing the mouldboard. Abrasion eventually destroys all parts of a plough that contact the soil.
On a vehicle such as a tram, a plough is also the name commonly given to the pair of shoes, one pick-up and one return, both attached to a busbar, that draw power from a pair of live rails underneath the road.
The seed drill was invented by Jethro Tull in 1701: It allowed farmers to sow seeds in well-spaced rows at specific depths. Prior to this farmers simply cast seeds on the ground, by hand, for them to grow where they landed (broadcasting). Some of the broadcast seeds were cast on unprepared ground where they never germinated, germinated prematurely only to be killed by frost or died from lack of access to water and nutrients.
This invention gave farmers much greater control over the depth that the seed was planted and the ability to cover the seeds without back-tracking. This greater control meant that seeds germinated consistently and in good soil.
Over the years seed drills have become more advanced and sophisticated but the technology has remained substantially the same. The first seed drills were small enough to be drawn by a single horse but the availability of steam and, later, gasoline tractors saw the development of larger and more efficient drills that allowed farmers to seed even larger tracts in a single day.
Recent improvements to drills allow seed-drilling without prior
tilling or otherwise preparing the soil. This means that soils subject
to erosion or moisture loss are protected until the seed germinates and
grows enough to keep the soil in place.
