Agriculture encompasses a wide variety of specialties. Cultivation of crops on arable land and the pastoral herding of livestock on rangeland remain at the foundation of agriculture. In the past century a distinction has been made between sustainable agriculture and intensive farming. Modern agronomy, plant breeding, pesticides and fertilizers, and technological improvements have sharply increased yields from cultivation. Selective breeding and modern practices in animal husbandry such as intensive pig farming (and similar practices applied to the chicken) have similarly increased the output of meat. The more exotic varieties of agriculture include aquaculture and tree farming.
The major agricultural products can be broadly grouped into foods, fibers, fuels, raw materials, pharmaceuticals and illegal drugs, and an assortment of ornamental or otherwise exotic products. In recent years plants have been used to grow biofuels, biopharmaceuticals, bioplastics, and pharmaceuticals. Specific foods include cereals, vegetables, fruits, and meat. Fibers include cotton, wool, hemp, silk and flax. Raw materials include lumber and bamboo. Drugs include tobacco, marijuana, opium, cocaine, digitalis, curare, eugenol, reserpine, pyrethrins, taxol) and other useful materials such as resins. Biofuels include methane from biomass, ethanol, and biodiesel. Cut flowers, nursery plants, tropical fish and birds for the pet trade are some of the ornamental products.
The history of agriculture has played a major role in human history, as agricultural progress has been a crucial factor in worldwide socio-economic change. Wealth-building and militaristic specializations rarely seen in hunter-gatherer cultures are commonplace in societies which practice agriculture. So, too, are arts such as epic literature and monumental architecture, as well as codified legal systems. When farmers became capable of producing food beyond the needs of their own families, others in their society were freed to devote themselves to projects other than food acquisition. Historians and anthropologists have long argued that the development of agriculture made civilization possible.
In 2007, an estimated 35 percent of the world's workers were employed in agriculture (from 42% in 1996). However, the relative significance of farming has dropped steadily since the beginning of industrialization, and in 2003 – for the first time in history – the services sector overtook agriculture as the economic sector employing the most people worldwide. Despite the fact that agriculture employs over one-third of the world's population, agricultural production accounts for less than five percent of the gross world product (an aggregate of all gross domestic products).
Many governments have subsidized agriculture to ensure an adequate food supply. These agricultural subsidies are often linked to the production of certain commodities such as wheat, corn (maize), rice, soybeans, and milk. These subsidies, especially when done by developed countries have been noted as protectionist, inefficient, and environmentally damaging. In the past century agriculture has been characterized by enhanced productivity, the use of synthetic fertilizers and pesticides, selective breeding, mechanization, water contamination, and farm subsidies. Proponents of organic farming such as Sir Albert Howard argued in the early 1900s that the overuse of pesticides and synthetic fertilizers damages the long-term fertility of the soil. While this feeling lay dormant for decades, as environmental awareness has increased recently there has been a movement towards sustainable agriculture by some farmers, consumers, and policymakers. In recent years there has been a backlash against perceived external environmental effects of mainstream agriculture, particularly regarding water pollution, resulting in the organic movement. One of the major forces behind this movement has been the European Union, which first certified organic food in 1991 and began reform of its Common Agricultural Policy (CAP) in 2005 to phase out commodity-linked farm subsidies, also known as decoupling. The growth of organic farming has renewed research in alternative technologies such as integrated pest management and selective breeding. Recent mainstream technological developments include genetically modified food.
As of late 2007, several factors have pushed up the price of grain used to feed poultry and dairy cows and other cattle, causing higher prices of wheat (up 58%), soybean (up 32%), and maize (up 11%) over the year. Food riots have recently taken place in many countries across the world. An epidemic of stem rust on wheat caused by race UG99 is currently spreading across Africa and into Asia and is causing major concern. Approximately 40% of the world's agricultural land is seriously degraded. In Africa, if current trends of soil degradation continue, the continent might be able to feed just 25% of its population by 2025, according to UNU's Ghana-based Institute for Natural Resources in Africa.
Agricultural practices lie on a spectrum dependent upon the intensity and technology of the methods. At the one end lies the subsistence farmer who farms a small area with limited inputs and produces only enough food to meet the needs of his or her family. At the other end lies intensive agriculture which includes traditional labor intensive farming (e.g. South-East Asia rice paddies), and modern agriculture which includes industrial agriculture, organic farming and sustainable farming. Industrial agriculture involves large fields and/or numbers of animals, high resource inputs (pesticides, fertilizers, etc.), and a high level of mechanization. These operations achieve economies of scale and require large amounts of capital in the form of land and machinery.
The twentieth century saw changes in agricultural practice, particularly in agricultural chemistry and in mechanization. Agricultural chemistry includes the application of chemical fertilizer, chemical insecticides (see pest control), and chemical fungicides, analysis of soil makeup and nutritional needs of farm animals.
Mechanization has increased farm efficiency and productivity in most regions of the world, due especially to the tractor and various "gins" (short for "engine") such as the cotton gin, semi-automatic balers and threshers and, above all, the combine (see agricultural machinery). According to the National Academy of Engineering in the United States, 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. By 1999, due to advances in agricultural technology, a single farmer could feed over 130 people.
Other recent changes in agriculture include hydroponics, plant breeding, hybridization, gene manipulation, better management of soil nutrients, and improved weed control. Genetic engineering has yielded crops which have capabilities beyond those of naturally occurring plants, such as higher yields and disease resistance. Modified seeds germinate faster, and thus can be grown on an accelerated schedule. Genetic engineering of plants has proven controversial, particularly in the case of herbicide-resistant plants.
It has been suggested that genetic engineers may some day develop transgenic plants which would allow for irrigation, drainage, conservation, sanitary engineering, and maintaining or increasing yields while requiring fewer fossil fuel derived inputs than conventional crops. Such developments would be particularly important in areas which are normally arid and rely upon constant irrigation, and on large scale farms. These possibilities are questioned by ecologists and economists concerned with unsustainable GMO practices such as terminator seeds, and a January 2008 report shows that GMO practices have failed to address sustainability issues. While there has been some research on sustainability using GMO crops, at least one hyped and promonant multi-year attempt by Monsanto has been unsuccessful, though during the same period traditional breeding techniques yielded a more sustainable variety of the same crop. Additionally, a survey by the bio-tech industry of subsistence farmers in Africa to discover what GMO research would most benefit sustainable agriculture only identified non-transgenic issues as areas needing to be addressed.
The processing, packing and marketing of agricultural products are closely related activities also influenced by science. Methods of quick-freezing and dehydration have increased the markets for many farm products (see food preservation and meat packing industry).
Animals, including horses, mules, oxen, camels, llamas, alpacas, and dogs, are often used to help cultivate fields, harvest crops, wrangle other animals, and transport farm products to buyers. Animal husbandry not only refers to the breeding and raising of animals for meat or to harvest animal products (like milk, eggs, or wool) on a continual basis, but also to the breeding and care of species for work and companionship.
Airplanes, helicopters, trucks, tractors, and combines are used in Western (and, increasingly, Eastern) agriculture for seeding, spraying operations for insect and disease control, harvesting, aerial topdressing and transporting perishable products. 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.
In recent years, some aspects of intensive industrial agriculture have been the subject of increasing debate. 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. Another issue is the type of feed given to some animals that can cause bovine spongiform encephalopathy in cattle. There has also been concern over the effect of intensive agriculture on the environment.
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. The Indian activist and scientist Vandana Shiva argues that these companies are guilty of biopiracy.
Soil conservation and nutrient management have been important concerns since the 1950s, with the most advanced farmers taking a stewardship role with the land they use. However, increasing contamination of waterways and wetlands by nutrients like nitrogen and phosphorus are concerns that can only be addressed by "enlightenment" of farmers and/or far stricter law enforcement in many countries.
Agriculture was developed at least 10,000 years ago, and it has undergone significant developments since the time of the earliest cultivation. Evidence points to the Fertile Crescent of the Middle East as the site of the earliest planned sowing and harvesting of plants that had previously been gathered in the wild. Independent development of agriculture occurred in northern and southern China, Africa's Sahel, New Guinea and several regions of the Americas. Agricultural practices such as irrigation, crop rotation, fertilizers, and pesticides were developed long ago but have made great strides in the past century. The Haber-Bosch method for synthesizing ammonium nitrate represented a major breakthrough and allowed crop yields to overcome previous constraints. In the past century agriculture has been characterized by enhanced productivity, the substitution of labor for synthetic fertilizers and pesticides, selective breeding, mechanization, water pollution, and farm subsidies. In recent years there has been a backlash against the external environmental effects of conventional agriculture, resulting in the organic movement.
Developed independently by geographically distant populations, systematic agriculture first appeared in Southwest Asia with the bulk of domesticated neolthic crops and livestock now being traced to Turkey via DNA studies. The first grains of domesticated Turkish emmer wheat are found at Abu Hurerya dated to 13,500 BP. The only exceptions to this are barley, domesticated in two sites; in Levant, and East of the Zagros mountains in Iran. The eight so-called founder crops of agriculture appear: first emmer and einkorn wheat, then hulled barley, peas, lentils, bitter vetch, chick peas and flax.Bitter vetch and lentils along with almonds and pistachios appear in Franchthi Cave Greece simultaneously, about 9,000 BC. Neither are native to Greece, and they appear 2,000 years prior to domesticated wheat in the same location. This suggests that the cultivation of legumes and nuts preceded that of grain.
By 7000 BCE, small-scale agriculture reached Egypt. From at least 7000 BCE the Indian subcontinent saw farming of wheat and barley, as attested by archaeological excavation at Mehrgarh in Balochistan. By 6000 BCE, mid-scale farming was entrenched on the banks of the Nile. About this time, agriculture was developed independently in the Far East, with rice, rather than wheat, as the primary crop. Chinese and Indonesian farmers went on to domesticate mung, soy, azuki and taro. To complement these new sources of carbohydrates, highly organized net fishing of rivers, lakes and ocean shores in these areas brought in great volumes of essential protein. Collectively, these new methods of farming and fishing inaugurated a human population boom dwarfing all previous expansions, and is one that continues today.
By 5000 BCE, the Sumerians had developed core agricultural techniques including large scale intensive cultivation of land, mono-cropping, organized irrigation, and use of a specialized labour force, particularly along the waterway now known as the Shatt al-Arab, from its Persian Gulf delta to the confluence of the Tigris and Euphrates. Domestication of wild aurochs and mouflon into cattle and sheep, respectively, ushered in the large-scale use of animals for food/fiber and as beasts of burden. The shepherd joined the farmer as an essential provider for sedentary and semi-nomadic societies.
Maize, manioc, and arrowroot were first domesticated in the Americas as far back as 5200 BCE. The potato, tomato, pepper, squash, several varieties of bean, Canna, tobacco and several other plants were also developed in the New World, as was extensive terracing of steep hillsides in much of Andean South America.
In later years, the Greeks and Romans built on techniques pioneered by the Sumerians but made few fundamentally new advances. Southern Greeks struggled with very poor soils, yet managed to become a dominant society for years. The Romans were noted for an emphasis on the cultivation of crops for trade.
During the Middle Ages, Muslim farmers in North Africa and the Near East developed and disseminated agricultural technologies including irrigation systems based on hydraulic and hydrostatic principles, the use of machines such as norias, and the use of water raising machines, dams, and reservoirs. They also wrote location-specific farming manuals, and were instrumental in the wider adoption of crops including sugar cane, rice, citrus fruit, apricots, cotton, artichokes, aubergines, and saffron. Muslims also brought lemons, oranges, cotton, almonds, figs and sub-tropical crops such as bananas to Spain.
Another important development towards the end of this period was the discovery and subsequent cultivation of fodder crops which allowed over-wintering of livestock.
After 1492, a global exchange of previously local crops and livestock breeds occurred. Key crops involved in this exchange included the tomato, maize, potato, cocoa and tobacco going from the New World to the Old, and several varieties of wheat, spices, coffee, and sugar cane going from the Old World to the New. The most important animal exportations from the Old World to the New were those of the horse and dog (dogs were already present in the pre-Columbian Americas but not in the numbers and breeds suited to farm work). Although not usually food animals, the horse (including donkeys and ponies) and dog quickly filled essential production roles on western hemisphere farms.
By the early 1800s, agricultural techniques, implements, seed stocks and cultivars had so improved that yield per land unit was many times that seen in the Middle Ages. With the rapid rise of mechanization in the late 19th and 20th centuries, particularly in the form of the tractor, farming tasks could be done with a speed and on a scale previously impossible. 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 2005, the agricultural output of China was the largest in the world, accounting for almost one-sixth world share followed by the EU, India and the USA, according to the International Monetary Fund. Economists measure the total factor productivity of agriculture and by this measure agriculture in the United States is roughly 2.6 times more productive than it was in 1948.
|Top agricultural products, by crop types |
(million metric tons) 2004 data
|Vegetables and melons||866|
|Roots and Tubers||715|
|Fish (2001 estimate)||130|
Food and Agriculture Organization (FAO)
|Top agricultural products, by individual crops |
(million metric tons) 2004 data
|Oil Palm Fruit||162|
Food and Agriculture Organization (FAO)
Domestication of plants has, over the centuries increased yield, improved disease resistance and drought tolerance, eased harvest and improved the taste and nutritional value of crop plants. Careful selection and breeding have had enormous effects on the characteristics of crop plants. Plant breeders use greenhouses (known as glasshouses or hothouses in some areas) and other techniques to get as many as three generations of plants per year towards the continued effort of improvement. Plant selection and breeding in the 1920s and 1930s improved pasture (grasses and clover) in New Zealand. Extensive X-ray an ultraviolet induced mutagenesis efforts (i.e. primitive genetic engineering) during the 1950s produced the modern commercial varieties of grains such as wheat, corn (maize) and barley.
For example, average yields of corn (maize) in the USA have increased from around 2.5 tons per hectare (t/ha) (40 bushels per acre) in 1900 to about 9.4 t/ha (150 bushels per acre) in 2001. 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. Variation in yields are due mainly to variation in climate, genetics, and the level of intensive farming techniques (use of fertilizers, chemical pest control, growth control to avoid lodging).
After mechanical tomato-harvesters were developed in the early 1960s, agricultural scientists bred tomatoes that were more resistant to mechanical handling. These varieties have been criticized as being harder and having poor texture. More recently, genetic engineering has begun to be employed in large parts of the world to speed up the selection and breeding process. One widely used modification is a herbicide resistance gene that allows plants to tolerate exposure to glyphosate, a non-systemic (i.e kills all plants) chemical used to control weeds in a crop such as oilseed rape. Normally, expensive systemic herbicides would have to be applied to kill the weeds without harming the crop. Relatively cheap and safe glyphosate may be applied to the modified crops, efficiently killing weeds without harming the resistant crop. Another modification causes the plant to produce a toxin to reduce damage from insects (c.f. Starlink). This, in contrast, requires fewer insecticides to be applied to the crop.
According to the United Nations, the livestock sector (primarily cows, chickens, and pigs) emerges as one of the top two or three most significant contributors to our most serious environmental problems, at every scale from local to global. Livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the planet.It is one of the largest sources of greenhouse gases—responsible for 18% of the world's greenhouse gas emissions as measured in CO2 equivalents. By comparison, all transportation emits 13.5% of the CO2. It produces 65% of human-related nitrous oxide (which has 296 times the global warming potential of CO2) and 37% of all human-induced methane (which is 23 times as warming as CO2). It also generates 64% of the ammonia, which contributes to acid rain and acidification of ecosystems.
Genetic erosion in crops and livestock biodiversity is propelled by several major factors such as variety replacement, land clearing, overexploitation of species, population pressure, environmental degradation, overgrazing, policy and changing agricultural systems.
The main factor, however, is the replacement of local varieties of domestic plants and animals by high yielding or exotic varieties or species. A large number of varieties can also often be dramatically reduced when commercial varieties (including GMOs) are introduced into traditional farming systems. Many researchers believe that the main problem related to agro-ecosystem management is the general tendency towards genetic and ecological uniformity imposed by the development of modern agriculture.
In agriculture and animal husbandry, the green revolution popularized the use of conventional hybridization to increase yield many folds by creating "high-yielding varieties". Often the handful of breeds of plants and animals hybridized originated in developed countries and were further hybridized with local varieties in the rest of the developing world to create high yield strains resistant to local climate and diseases. Hybridization of local breeds to improve performance may lead to the loss of the local breed over time and consequently the loss of specific genetic material due to dilution. When viewed across the world as a whole, the consequent loss in genetic diversity and biodiversity could place agriculture in a situation unable to adapt to sudden changes in the future.
A Genetically Modified Organism (GMO) is an organism whose genetic material has been altered using the genetic engineering techniques generally known as recombinant DNA technology. Genetic engineering has vastly expanded the repertoire of genes available to breeders to create the desired properties in future germlines. However, it is hypothesised that these new strains will replace the wild-type species beyond their original fields, and that these genes may be transferred to other plant species that were not intended.
Besides these phases, the constellation of the zodiac through which the moon is passing is also observed. This is used to make further timing decisions for various farming operations. For instance, when the moon is in Cancer it is believed to be the best time to sow seeds and start planting, however when it is in Aries, a barren sign, planting should be avoided.
The moon's gravitation is known to affect large bodies of water on the earth such as seas and oceans creating tides. It is conjectured that it also produces effects on a smaller scale; affecting the water contained in soils and plants. This explains the mechanism buy which plants are affected by the phases of the moon.
One example of the chain reactions which could possibly be caused by peak oil issues involves the problems caused by farmers raising crops such as corn (maize) for non-food use in an effort to help mitigate peak oil. This has already lowered food production. This food vs fuel issue will be exacerbated as demand for ethanol fuel rises. Rising food and fuel costs has already limited the abilities of some charitable donors to send food aid to starving populations. In the UN, some warn that the recent 60% rise in wheat prices could cause "serious social unrest in developing countries." In 2007, higher incentives for farmers to grow non-food biofuel crops combined with other factors (such as over-development of former farm lands, rising transportation costs, climate change, growing consumer demand in China and India, and population growth) to cause food shortages in Asia, the Middle East, Africa, and Mexico, as well as rising food prices around the globe. As of December 2007, 37 countries faced food crises, and 20 had imposed some sort of food-price controls. Some of these shortages resulted in food riots and even deadly stampedes.
Another major petroleum issue in agriculture is the effect of petroleum supplies will have on fertilizer production. By far the biggest fossil fuel input to agriculture is the use of natural gas as a hydrogen source for the Haber-Bosch fertilizer-creation process. Natural gas is used because it is the cheapest currently available source of hydrogen. When oil production becomes so scarce that natural gas is used as a partial stopgap replacement, and hydrogen use in transportation increases, natural gas will become much more expensive. If other sources of hydrogen are not available to replace the Haber process, in amounts sufficient to supply transportation and agricultural needs, this major source of fertilizer would either become extremely expensive or unavailable. This would either cause food shortages or dramatic rises in food prices.
It has been suggested that rural communities might obtain fuel from the biochar and synfuel process, which uses agricultural waste to provide charcoal fertilizer, some fuel and food, instead of the normal food vs fuel debate. As the synfuel would be used on site, the process would be more efficient and may just provide enough fuel for a new organic-agriculture fusion.
It has been suggested that some transgenic plants may some day be developed which would allow for maintaining or increasing yields while requiring fewer fossil fuel derived inputs than conventional crops. The possibility of success of these programs is questioned by ecologists and economists concerned with unsustainable GMO practices such as terminator seeds, and a January 2008 report shows that GMO practices "fail to deliver environmental, social and economic benefits. While there has been some research on sustainability using GMO crops, at least one hyped and prominent multi-year attempt by Monsanto has been unsuccessful, though during the same period traditional breeding techniques yielded a more sustainable variety of the same crop. Additionally, a survey by the bio-tech industry of subsistence farmers in Africa to discover what GMO research would most benefit sustainable agriculture only identified non-transgenic issues as areas needing to be addressed. Nonetheless, some governments in Africa continue to view investments in new transgenic technologies as an essential component of efforts to improve sustainability.
For young agricultural workers aged 15–17, the risk of fatal injury is four times the risk for young workers in other workplaces Agricultural work exposes young workers to safety hazards such as machinery, confined spaces, work at elevations, and work around livestock.