Agriculture
Agriculture
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Agriculture
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General
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Agronomy
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Farm
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History
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Types
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Grazing
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Orchard
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Agriculture, also called farming or husbandry,
is the cultivation of animals, plants, fungi, and other life forms forfood, fiber, biofuel. drugs and other products used to sustain
and enhance human life.[1] Agriculture
was the key development in the rise of sedentary human civilization, whereby
farming of domesticated species
created foodsurpluses that
nurtured the development of civilization. The
study of agriculture is known as agricultural
science. Thehistory of agriculture dates back thousands of
years, and its development has been driven and defined by greatly
different climates, cultures,
and technologies. However, all farming generally relies on techniques to expand
and maintain the lands that are suitable for raising domesticated species. For
plants, this usually requires some form ofirrigation, although
there are methods of dryland
farming; pastoral herding
on rangeland is
still the most common means of raising livestock. In the developed world, industrial agriculture based on
large-scale monoculture has
become the dominant system of modern farming, although there is growing support
for sustainable agriculture (e.g.permaculture or organic
agriculture).
Until the Industrial Revolution, the vast majority of the human
population labored in agriculture. Pre-industrial agriculture was
typically subsistence agriculture in which farmers raised
most of their crops for their own consumption instead of for trade. A
remarkable shift in agricultural practices has occurred over the past century
in response to new technologies, and the development of world markets. This
also led to technological improvements in agricultural techniques, such as
the Haber-Bosch method
for synthesizing ammonium
nitrate which made the traditional practice of recycling nutrients with crop rotation and
animal manure less
necessary.
Modern agronomy, plant breeding,
and agrochemicals such
as pesticides and fertilizers, and
technological improvements have sharply increased yields from cultivation, but
at the same time have caused widespread ecological damage and negative human
health effects. Selective
breeding and modern practices in animal husbandry such as intensive pig farming have similarly increased
the output of meat, but have raised concerns about animal welfare and
the health effects of the antibiotics, growth hormones, and
other chemicals commonly used in industrial meat production.
The major agricultural
products can be broadly grouped into foods, fibers, fuels, and raw materials.
Specific foods include cereals, vegetables, fruits, and meat. Fibers include cotton, wool, hemp, silk and flax. Raw materials includelumber and bamboo. Other useful materials are produced by
plants, such as resins. Biofuels
include methane frombiomass, ethanol, and biodiesel. Cut flowers, nursery plants, tropical fish and birds for the pet
trade are some of the ornamental products. Agricultural food production and
water management is targeted as an increasingly global issue that is fostering
an important and growing debate.
In 2011, one third of the
world's workers were employed in agriculture, second only to the services
sector. Despite the size of its workforce, agricultural production accounts for
less than five percent of the gross
world product (an aggregate of all gross domestic products).
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The word agriculture is
a late Middle
English adaptation of Latin agricultūra, from ager,
"field", and cultūra, "cultivation" or
"growing".[2] Agriculture
usually refers to human activities, although it is also observed in certain
species of ant, termite and ambrosia beetle.[3] To
practice agriculture means to use natural resources to "produce
commodities which maintain life, including food, fiber, forest products,
horticultural crops, and their related services."[4] This
definition includeshorticulture (the
growing of plants), animal
husbandry and forestry.[4] A
distinction is sometimes made between forestry and agriculture, based on the
former's longer management rotations, extensive versus intensive management
practices and development mainly by nature, rather than by man. Even then, it
is acknowledged that there is a large amount of knowledge transfer and overlap
between silviculture (the
management of forests) and agriculture.[5]
Main
article: History of agriculture
A Sumerian harvester's sickle made from
baked clay (ca. 3000 BC).
Agricultural practices such
as irrigation, crop rotation, fertilizers, pesticides and animals were
developed a long time ago, but have made great progress in the past century.
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. Division
of labor in agricultural societies made commonplace
specializations rarely seen in hunter-gatherer cultures.
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. The total world population probably
never exceeded 15 million inhabitants before the development of agriculture.[6]
Forest gardening, a
plant-based food production system, is thought to be the world's oldest agroecosystem.[7] Forest
gardens originated in prehistoric times
along jungle-clad river banks and in the wet foothills of monsoon regions.
In the gradual process of a family improving their immediate environment,
useful tree and vine species were identified, protected and improved whilst
undesirable species were eliminated. Eventually superior foreign species were
selected and incorporated into the family's garden.[8]
Further
information: Neolithic
Revolution
Threshing of grain in
ancient Egypt
The Fertile Crescent of
the Near East first
saw the domestication of animals, starting the Neolithic Revolution. Between
10,000 and 13,000 years ago, the ancestors of modern cattle, sheep, goats and
pigs were domesticated in this area. The gradual transition from wild
harvesting to deliberate cultivation happened independently in several areas
around the globe.[9] Agriculture
allowed for the support of an increased population, leading to larger societies
and eventually the development of cities. It also created the need for greater
organization of political power (and the creation of social stratification), as decisions had to be made
regarding labor and harvest allocation and access rights to water and land.
Agriculture bred immobility, as populations settled down for long periods of
time, which led to the accumulation of material goods.[10]
Early Neolithic villages
show evidence of the ability to process grain, and the Near East is the ancient
home of the ancestors of wheat, barley and peas. There is evidence of the cultivation
of figs in
the Jordan Valley as long as 11,300 years ago,
and cereal (grain)
production in Syria approximately 9,000 years ago. During the same period,
farmers in China began to farm rice and millet, using man-made floods and fires as
part of their cultivation regimen.[9] Fiber
crops were domesticated as early as food crops, with China domesticating hemp, cottonbeing developed independently in Africa
and South America and the Near East domesticating flax.[11] The
use of soil amendments, including manure, fish, compost and ashes, appears to
have begun early, and developed independently in several areas of the world,
including Mesopotamia,
the Nile Valley and
eastern Asia.[12]
Squash was
grown in Mexico nearly 10,000 years ago, while maize-like plants, derived from
the wild teosinte began
to be seen at around 9,000 years ago. The derivation of teosinte into modern
corn was slow, however, and it took until 5,500[9] to
6,000 years ago to turn into what we know today as maize. It then gradually
spread across North America and was the major crop of Native Americans at the
time of European exploration.[13] Beans were domesticated around the same
time, and together these three plants formed the Three Sisters nutritional foundation of many
native populations in North and Central America. Combined with peppers, these
crops provided a balanced diet for much of the continent.[14] Grapes were first grown for wine approximately 8,000 years ago, in
the Southern
Caucasus, and by 3000 BC had spread to the Fertile Crescent, the
Jordan Valley and Egypt.[15]
Roman harvesting machine
Agriculture advanced to
Europe slightly later, reaching the northeast of the continent from the east
around 4000 BC. The idea that agriculture spread to Europe, rather than
independently developing there, has led to two main hypotheses. The first is a "wave
of advance", which holds that agriculture traveled slowly and steadily
across the continent, while the second, "population pulse" theory,
holds that it moved in jumps.[16] Around
5,000 years ago,sunflowers were
first cultivated in North America, while South America's Andes region was developing the potato.[9] A
minor center of domestication, the indigenous people of the eastern US appear
to have domesticated numerous crops, including tobacco.[17]
Between 2500 and 2000 BC,
the simplest form of the plough,
called the ard,
spread throughout Europe, replacing the hoe. This change in
equipment significantly increased cultivation ability, and affected the demand
for land, as well as ideas about property, inheritance and family rights.[18] Before
this period, simple digging
sticks or hoes were used. These tools would have also been
easier to transport, which was a benefit as people only stayed until the soil's
nutrients were depleted. However, through excavations in Mexico it has been
found that the continuous cultivating of smaller pieces of land would also have
been a sustaining practice. Additional research in central Europe later
revealed that agriculture was indeed practiced at this method. For this method,
ards were thus much more efficient than digging sticks.[19]
During the time of
the Greco-Romans,
scholars, including Plato (428-348
BC) and Aristotle (384-322
BC) documented farming techniques, including the use of fertilizers. Much of
what scholars believed about farming and plant nutrition at this time was later
found to be incorrect, but their theories provided the scientific foundation
for the development of agricultural theories through the Middle Ages. Ideas
about soil fertility and fertilization remained much the same from the time of
Greco-Roman scholars until the 19th century, with correspondingly low crop
yields.[12]
Agricultural calendar from
a manuscript of Pietro
de Crescenzi.
The Middle Ages saw
significant improvements in the agricultural techniques and technology. During
this time period, monasteries, originally developed in Greece and the Middle
East, spread throughout Europe and became important centers for the collection
of knowledge related to agriculture and forestry. The manorial system,
which existed under different names throughout Europe and Asia, allowed large
landowners significant control over both their land and its laborers, in the
form of peasants or serfs.[20]
By 900 AD in Europe,
developments in iron
smelting allowed for increased production, leading to
developments in the production of agricultural implements such as ploughs, hand
tools and horse
shoes. The plough was significantly improved, developing into
the mouldboard
plough, capable of turning over the heavy, wet soils of northern
Europe. This led to the clearing of forests in that area and a significant
increase in agricultural production, which in turn led to an increase in
population.[21] A
similar plough, which may have developed independently, was also found in China
as early as the 9th century.[22] At
the same time, farmers in Europe moved from a two field crop rotation to
a three field crop rotation in which one field of three was left fallow every
year. This resulted in increased productivity and nutrition, as the change in
rotations led to different crops being planted, including legumes such as
peas, lentils and beans. Inventions such as improved horse harnesses and
the whippletree also changed methods of cultivation.[21] Watermillswere
initially developed by the Romans, but were improved throughout the Middle
Ages, along with windmills,
and used to grind grains into flour, cut wood and process flax and wool, among
other uses.[23]
Crops were wheat, rye, barley, and oats. Peas, beans, and vetches became
common from the 13th century onward as a fodder crop for
animals and also for theirnitrogen-fixation fertilizing
properties. Crop yields peaked in the 13th century, and according to Bruce
Campbell and Mark Overton stayed more or less steady until the 18th century.[24] Though
the limitations of medieval farming were once thought to have provided a
ceiling for the population growth in the Middle Ages, recent studies by Campbell[25] and
David Stone[26] have
shown that the technology of medieval agriculture was always sufficient for the
needs of the people under normal circumstances, and that it was only during
exceptionally harsh times, such as the terrible weather of 1315–17, that the needs of the
population could not be met.[27]
The Harvesters. Pieter Bruegel. 1565.
_CNE-v1-p58-H.jpg)
Infrared image
of the above farms. Various colors indicate healthy crops (red), flooding
(black) and unwanted pesticides (brown).
After 1492, a global
exchange of previously local crops and livestock breeds
occurred. Key crops involved in this exchange included maize, potatoes, sweet potatoes and manioc traveling from the New World to
the Old, and several varieties of wheat, barley, rice and turnips going from the Old World to the
New. There were very few livestock species in the New World, with horses,
cattle, sheep and goats being completely unknown before their arrival with Old
World settlers. Crops moving in both directions across the Atlantic Ocean caused
population growth around the world, and had a lasting effect on many cultures.[28] Since
being introduced by Portuguese in the 16th century,[29] maize
andmanioc have
replaced traditional African crops as the continent's most important staple
food crops.[30]
After its introduction from
South America to Spain in the late 1500s, the potato became an important staple
crop throughout Europe by the late 1700s. The potato allowed farmers to produce
more food, and initially added variety to the European diet. The nutrition
boost caused by increased potato consumption resulted in lower disease rates,
higher birth rates and lower mortality rates, causing a population boom
throughout the British Empire, the US and Europe.[31] The
introduction of the potato also brought about the first intensive use of
fertilizer, in the form of guanoimported
to Europe from Peru, and the first artificial pesticide, in the form of
an arsenic compound
used to fightColorado potato beetles. Before the adoption of the
potato as a major crop, the dependence on grain caused repetitive regional and
national famines when the crops failed: 17 major famines in England alone
between 1523 and 1623. Although initially almost eliminating the danger of
famine, the resulting dependence on the potato eventually caused the European Potato Failure, a disastrous crop failure
resulting in widespread famine, and the death of over one million people in
Ireland alone.[32]
By the early 19th century,
agricultural techniques, implements, seed stocks and cultivar had so
improved that yield per land unit was many times that seen in the Middle Ages.
The work of Charles
Darwin and Gregor Mendel created
the scientific foundation for plant breeding that led to its explosive impact
over the past 150 years.[33] With
the rapid rise ofmechanization in the late 19th century and the
20th century, 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 modern farms to output volumes of
high-quality produce per land unit.[34]
In 1909 the Haber-Bosch method
to synthesize ammonium
nitrate was first demonstrated; it represented a major
breakthrough and allowed crop
yields to overcome previous constraints. In the years
after World
War II, the use of synthetic fertilizer increased rapidly, in sync
with the increasing world population.[35] In
the past century agriculture has been characterized by increased productivity,
the substitution of synthetic fertilizers and pesticides for labor, 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.[36]
The cereals rice, corn, and
wheat provide 60% of human food supply.[37] Between
1700 and 1980, "the total area of cultivated land worldwide increased
466%" and yields increased dramatically, particularly because of selectively
bredhigh-yielding varieties, fertilizers, pesticides, irrigation,
and machinery.[37] However,
concerns have been raised over the sustainability of
intensive agriculture. Intensive agriculture has become associated with
decreased soil quality in India and Asia, and there has been increased concern
over the effects of fertilizers and pesticides on the environment, particularly
as population increases and food demand expands. The monocultures typically
used in intensive agriculture increase the number of pests, which are
controlled through pesticides. Integrated pest management (IPM), which
"has been promoted for decades and has had some notable successes"
has not significantly affected the use of pesticides because policies encourage
the use of pesticides and IPM is knowledge-intensive.[37]
Since the late 19th
century, agricultural exploration expeditions have been mounted to find new
species and new agricultural practices in different areas of the world. Two
early American examples of expeditions include Frank N. Meyer's fruit- and
nut-collecting trip to China and Japan from 1916 to 1918[38] and
the Dorsett-Morse Oriental Agricultural Exploration Expedition to China, Japan,
and Korea from 1929–1931 to collect soybean germplasm to support the rise in
soybean agriculture in the United States.[39] In
the 21st century, plants have been used to grow biofuels, pharmaceuticals (including biopharmaceuticals),[40] and bioplastics.[41]
Main
article: Green
Revolution
Norman Borlaug,
father of the Green Revolution, is often credited with saving over a billion
people worldwide from starvation.
The Green Revolution refers
to a series of research, development, and technology
transfer initiatives, occurring between the 1940s and the late
1970s, that increased agriculture production around the world, beginning most
markedly in the late 1960s.[42] The
initiatives, led by Norman
Borlaug, the "Father of the Green Revolution" credited
with saving over a billion people from starvation, involved the development of
high-yielding varieties of cereal grains, expansion of irrigation
infrastructure, modernization of management techniques, distribution of
hybridized seeds, syntheticfertilizers,
and pesticides to
farmers.
Synthetic nitrogen, along
with mined rock
phosphate, pesticides and mechanization, have greatly increased crop yields in
the early 20th century. Increased supply of grains has led to cheaper livestock as
well. Further, global yield increases were experienced later in the 20th
century when high-yield varieties of common staple grains such as rice, wheat, and corn (maize) were introduced as a part of the Green
Revolution. The Green Revolution exported the technologies (including
pesticides and synthetic nitrogen) of the developed world to the developing
world. Thomas
Malthus famously predicted that the Earth would not be able to
support its growing population, but technologies such as the Green Revolution
have allowed the world to produce a surplus of food.[43]
Although the Green
Revolution significantly increased rice yields in Asia, yield increases have
not occurred in the past 15–20 years.[44] The
genetic "yield potential" has increased for wheat, but the yield
potential for rice has not increased since 1966, and the yield potential for
maize has "barely increased in 35 years".[44] It
takes a decade or two for herbicide-resistant weeds to emerge, and insects
become resistant to insecticides within about a decade.[44] Crop
rotation helps to prevent resistances.[44]
Clark's Sector Model (1950): The percent of the human
population working in primary
sector activities such as agriculture has decreased over time.
In the past century
agriculture has been characterized by enhanced productivity, the
use of syntheticfertilizers and
pesticides, selective
breeding, mechanization, water
contamination, and farm subsidies.
Proponents of organic
farming such as Sir Albert Howard argued
in the early 20th century 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 in the
21st century there has been a movement towards sustainable agriculture by some farmers,
consumers, and policymakers.
Since the 1990s, there has
been a backlash against perceived external environmental
effects of mainstream agriculture, particularly regarding water pollution,[45] 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,[46] 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.
In late 2007, several
factors pushed up the price of grains consumed by humans as well as 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. Contributing
factors included increased demand for grain-fed animal products from the
growing middle classes of countries such as China and India and the diversion
of food grain to biofuel production.[47][48] Food riots took place in several countries
across the world.[49][50][51] The International Fund for Agricultural Development posits
that an increase in smallholder
agriculture may be part of the solution to concerns about food
prices and overall food security. They in part base this on the experience of
Vietnam, which went from a food importer to large food exporter and saw a
significant drop in poverty, due mainly to the development of smallholder
agriculture in the country.[52]
An epidemic of stem rust on
wheat caused by race Ug99 is
currently spreading across Africa and into Asia and is causing major concern.[53][54][55] Approximately
40% of the world's agricultural land is seriously degraded.[56] 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.[57]
In 2009, the agricultural
output of China was the largest in the world, followed by the
European Union, India and the United States, according to the International Monetary Fund (see
below). Economists measure the total factor productivity of agriculture and by
this measure agriculture in the United States is roughly 1.7 times more
productive than it was in 1948.[58] Six
countries – the US, Canada, France, Australia, Argentina and Thailand – supply
90% of grain
exports.[59] Water deficits,
which are already spurring heavy grain imports in numerous middle-sized
countries, including Algeria, Iran, Egypt, and Mexico,[60] may
soon do the same in larger countries, such as China or India.[61]
The Food and Agriculture
Organization of the United Nations (FAO) leads international
efforts to defeat hunger and provides forum for the negotiation of global
agricultural regulations and agreements. Dr. Samuel Jutzi, director of FAO's
animal production and health division, states that lobbying by large
corporations has stopped reforms that would improve human health and the
environment. For example, proposals in 2010 for a voluntary code of conduct for
the livestock industry that would have provided incentives for improving
standards for health, and environmental regulations, such as the number of
animals an area of land can support without long-term damage, were successfully
defeated due to large food company pressure.[62]
As of 2011, the International Labour Organization states that
approximately one billion people, or over 1/3 of the available work force, are
employed in the global agricultural sector. Agriculture constitutes
approximately 70 percent of the global employment of children, and in many
countries employs the largest percentage of women of any industry.[63] In
2007, the services sector overtook the agricultural sector as the largest
employer. Between 1997 and 2007, the percentage of people employed in
agriculture fell by over four percentage points, a trend that is expected to
continue.[64] The
number of people employed in agriculture varies widely on a per-country basis,
ranging from less than 2 percent in countries like the US and Canada to over 80
percent in many African nations.[65]
These figures are
significantly lower than in previous centuries. During the 16th century in
Europe, for example, between 55 and 75 percent of the population was engaged in
agriculture, depending on the country. By the 19th century in Europe, this had
dropped to between 35 and 65 percent.[66] In
the same countries today, the figure is less than 10 percent.[65]
Rollover protection bar on a Fordsontractor.
Agriculture remains a
hazardous industry, and farmers worldwide remain at high risk of work-related
injuries, lung disease, noise-induced hearing loss, skin diseases, as well as
certain cancers related to chemical use and prolonged sun exposure. On industrialized farms, injuries frequently involve the
use of agricultural machinery, and a common cause of fatal
agricultural injuries in developed countries is tractor rollovers.[67] Pesticides
and other chemicals used in farming can also be hazardous to worker health, and
workers exposed to pesticides may experience illnesses or birth defects.[68] As
an industry in which families commonly share in work and live on the farm
itself, entire families can be at risk for injuries, illness, and death.[69] Common
causes of fatal injuries among young farm workers include drowning, machinery
and motor vehicle-related accidents.[69]
The International Labour
Organization considers agriculture "one of the most hazardous of all
economic sectors."[63] It
estimates that the annual work-related death toll among agricultural employees
is at least 170,000, twice the average rate of other jobs. In addition,
incidences of death, injury and illness related to agricultural activities
often go unreported.[70] The
organization has developed the Safety and Health in
Agriculture Convention, 2001, which covers the range of risks in the
agriculture occupation, the prevention of these risks and the role that
individuals and organizations engaged in agriculture should play.[63]
Rice cultivation at a paddy
field in Biharstate of India
The Banaue
Rice Terraces in Ifugao, Philippines.
Cropping systems vary among
farms depending on the available resources and constraints; geography and
climate of the farm; government policy; economic, social and political
pressures; and the philosophy and culture of the farmer.[71][72]
Shifting
cultivation (or slash and burn) is a
system in which forests are burnt, releasing nutrients to support cultivation
of annual and then perennial crops
for a period of several years.[73] Then
the plot is left fallow to regrow forest, and the farmer moves to a new plot,
returning after many more years (10–20). This fallow period is shortened if
population density grows, requiring the input of nutrients (fertilizer or manure) and some manual pest control. Annual
cultivation is the next phase of intensity in which there is no fallow period.
This requires even greater nutrient and pest control inputs.
Further industrialization
lead to the use of monocultures,
when one cultivar is
planted on a large acreage. Because of the low biodiversity,
nutrient use is uniform and pests tend to build up, necessitating the greater
use of pesticides and
fertilizers.[72] Multiple
cropping, in which several crops are grown sequentially in one year, and intercropping, when
several crops are grown at the same time are other kinds of annual cropping
systems known as polycultures.[73]
In subtropical and arid environments, the timing and extent
of agriculture may be limited by rainfall, either not allowing multiple annual
crops in a year, or requiring irrigation. In all
of these environments perennial crops are grown (coffee, chocolate) and systems
are practiced such as agroforestry.
In temperate environments,
where ecosystems were predominantly grassland or prairie, highly
productive annual cropping is the dominant farming system.[73]
The last century has seen
the intensification, concentration and specialization of agriculture, relying upon new
technologies of agricultural chemicals (fertilizers and pesticides), mechanization, and plant breeding (hybrids and GMO's). In the past few decades, a move
towards sustainability in agriculture has also
developed, integrating ideas of socio-economic justice and conservation of
resources and the environment within a farming system.[74][75] This
has led to the development of many responses to the conventional agriculture
approach, including organic
agriculture, urban agriculture, community supported agriculture, ecological or
biological agriculture, integrated
farming and holistic management, as well as an increased trend
towards agricultural diversification.
Important categories of
crops include grains and pseudograins, pulses (legumes), forage, and
fruits and vegetables. Specific crops are cultivated in distinctgrowing regions throughout
the world. In millions of metric tons, based on FAO estimate.
|
Top agricultural products, by crop types
(million tonnes) 2004 data |
|
|
Cereals
|
2,263
|
|
Vegetables
and melons
|
866
|
|
715
|
|
|
Milk
|
619
|
|
Fruit
|
503
|
|
Meat
|
259
|
|
133
|
|
|
Fish
(2001 estimate)
|
130
|
|
63
|
|
|
60
|
|
|
30
|
|
|
Top agricultural products, by individual crops
(million tonnes) 2011 data |
|
|
Sugar
cane
|
1794
|
|
Maize
|
883
|
|
Rice
|
722
|
|
Wheat
|
704
|
|
Potatoes
|
374
|
|
Sugar
beet
|
271
|
|
Soybeans
|
260
|
|
Cassava
|
252
|
|
Tomatoes
|
159
|
|
Barley
|
134
|
Main
article: Livestock
Ploughing rice paddies
with water
buffalo, in Indonesia.
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.
Livestock production systems can be defined based on feed source, as grassland –
based, mixed, and landless.[77]
Grassland based livestock
production relies upon plant material such as shrubland, rangeland, and pastures for feeding ruminant animals.
Outside nutrient inputs may be used, however manure is returned directly to the
grassland as a major nutrient source. This system is particularly important in
areas where crop production is not feasible because of climate or soil,
representing 30–40 million pastoralists.[73] Mixed
production systems use grassland, foddercrops and grain feed crops as feed for
ruminant and monogastic (one stomach; mainly chickens and pigs) livestock.
Manure is typically recycled in mixed systems as a fertilizer for crops.
Approximately 68% of all agricultural land is permanent pastures used in the
production of livestock.[78]
Landless systems rely upon
feed from outside the farm, representing the de-linking of crop and livestock
production found more prevalently in OECD member countries. In the U.S., 70%
of the grain grown is fed to animals on feedlots.[73] Some
of the practices used in commercial livestock production, including the usage
of growth
hormones, are controversial.[79] Synthetic
fertilizers are more heavily relied upon for crop production and manure
utilization becomes a challenge as well as a source for pollution.
Road leading across the
farm allows machinery access to the farm for production practices.
Tillage is the
practice of plowing soil to prepare for planting or for nutrient incorporation
or for pest control. Tillage varies in intensity from conventional to no-till. It may
improve productivity by warming the soil, incorporating fertilizer and
controlling weeds, but also renders soil more prone to erosion, triggers the
decomposition of organic matter releasing CO2, and reduces the
abundance and diversity of soil organisms.[80][81]
Pest control includes
the management of weeds, insects/mites,
and diseases. Chemical (pesticides),
biological (biocontrol),
mechanical (tillage), and
cultural practices are used. Cultural practices includecrop rotation, culling, cover crops, intercropping, composting,
avoidance, and resistance. Integrated pest management attempts to use all
of these methods to keep pest populations below the number which would cause
economic loss, and recommends pesticides as a last resort.[82]
Nutrient
management includes both the source of nutrient inputs for crop
and livestock production, and the method of utilization of manure produced by livestock. Nutrient
inputs can be chemical inorganic fertilizers, manure, green manure, compost and
minedminerals.[83] Crop
nutrient use may also be managed using cultural techniques such as crop rotation or
a fallow period.[84][85] Manure
is used either by holding livestock where the feed crop is growing, such as
in managed intensive rotational grazing, or by
spreading either dry or liquid formulations of manure on cropland or pastures.
Water management is
where rainfall is insufficient or variable, which occurs to some degree in most
regions of the world.[73] Some
farmers use irrigation to
supplement rainfall. In other areas such as the Great Plains in
the U.S. and Canada, farmers use a fallow year to conserve soil moisture to
use for growing a crop in the following year.[86] Agriculture
represents 70% of freshwater use worldwide.[87]
Main
article: Plant
breeding
.jpg)
Tractor and Chaser bin
Crop alteration has been
practiced by humankind for thousands of years, since the beginning of
civilization. Altering crops through breeding practices changes the genetic
make-up of a plant to develop crops with more beneficial characteristics for
humans, for example, larger fruits or seeds, drought-tolerance, or resistance
to pests. Significant advances in plant breeding ensued after the work of
geneticist Gregor Mendel. His work on dominant and recessive alleles, although
initially largely ignored for almost 50 years, gave plant breeders a better
understanding of genetics and breeding techniques. Crop breeding includes
techniques such as plant selection with desirable traits, self-pollination and
cross-pollination, and molecular techniques that genetically modify the
organism.[88]
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 selection and breeding in the 1920s and 1930s improved
pasture (grasses and clover) in New Zealand. Extensive X-ray and 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.[89][90]
The Green Revolution popularized
the use of conventional hybridization to
increase yield many folds by creating "high-yielding varieties". 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. Variations 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).[91][92][93]
Main
article: Genetic
engineering
See
also: Genetically modified food, Genetically modified crops, Regulation of the release of
genetic modified organisms, and Genetically modified food controversies
Genetically Modified Organisms (GMO) are organisms whose genetic material
has been altered by genetic engineering techniques generally known asrecombinant DNA technology. Genetic engineering has
expanded the genes available to breeders to utilize in creating desired
germlines for new crops. Increased durability, nutritional content, insect and
virus resistance and herbicide tolerance are a few of the attributes bred into crops
through genetic engineering.[94] For
some, GMO crops cause food
safety and food labeling concerns. Numerous countries have
placed restrictions on the production, import and/or use of GMO foods and
crops, which have been put in place due to concerns over potential health
issues, declining agricultural diversity and contamination of non-GMO crops.[95] Currently
a global treaty, the Biosafety
Protocol, regulates the trade of GMOs. There is ongoing discussion
regarding the labeling of foods made from GMOs, and while the EU currently
requires all GMO foods to be labeled, the US does not.[96]
Herbicide-resistant seed
has a gene implanted into its genome that allows the plants to tolerate
exposure to herbicides, including glyphosates. These
seeds allow the farmer to grow a crop that can be sprayed with herbicides to
control weeds without harming the resistant crop. Herbicide-tolerant crops are
used by farmers worldwide.[97] With
the increasing use of herbicide-tolerant crops, comes an increase in the use of
glyphosate-based herbicide sprays. In some areas glyphosate resistant weeds
have developed, causing farmers to switch to other herbicides.[98][99] Some
studies also link widespread glyphosate usage to iron deficiencies in some
crops, which is both a crop production and a nutritional quality concern, with
potential economic and health implications.[100]
Other GMO crops used by
growers include insect-resistant crops, which have a gene from the soil
bacterium Bacillus thuringiensis (Bt), which produces
a toxin specific to insects. These crops protect plants from damage by insects.[101] Some
believe that similar or better pest-resistance traits can be acquired through
traditional breeding practices, and resistance to various pests can be gained
through hybridization or cross-pollination with wild species. In some cases,
wild species are the primary source of resistance traits; some tomato cultivars
that have gained resistance to at least 19 diseases did so through crossing
with wild populations of tomatoes.[102]
Main
article: Environmental issues with agriculture
Agriculture imposes external costs upon
society through pesticides, nutrient runoff, excessive water usage, and
assorted other problems. A 2000 assessment of agriculture in the UK determined
total external
costs for 1996 of £2,343 million, or £208 per hectare.[103] A
2005 analysis of these costs in the USA concluded that cropland imposes
approximately $5 to 16 billion ($30 to $96 per hectare), while livestock
production imposes $714 million.[104] Both
studies, which focused solely on the fiscal impacts, concluded that more should
be done to internalize external costs. Neither included subsidies in their
analysis, but they noted that subsidies also influence the cost of agriculture
to society.[103][104] In
2010, the International Resource Panel of the United Nations Environment Programme published
a report assessing the environmental impacts of consumption and production. The
study found that agriculture and food consumption are two of the most important
drivers of environmental pressures, particularly habitat change, climate
change, water use and toxic emissions.[105]
A senior UN official and
co-author of a UN report detailing this problem, Henning Steinfeld, said
"Livestock are one of the most significant contributors to today's most
serious environmental problems".[106] 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 emission. Livestock expansion is cited as a key factor driving
deforestation, in the Amazon basin 70% of previously forested area is now
occupied by pastures and the remainder used for feedcrops.[107] Through
deforestation and land degradation, livestock is also driving reductions in
biodiversity.
Land transformation, the
use of land to yield goods and services, is the most substantial way humans
alter the Earth's ecosystems, and is considered the driving force in the loss
of biodiversity. Estimates of the amount of land transformed by humans vary from
39–50%.[108] Land degradation,
the long-term decline in ecosystem function and productivity, is estimated to
be occurring on 24% of land worldwide, with cropland overrepresented.[109] The
UN-FAO report cites land management as the driving factor behind degradation
and reports that 1.5 billion people rely upon the degrading land. Degradation
can be deforestation,desertification, soil erosion,
mineral depletion, or chemical degradation (acidification and salinization).[73]
Eutrophication,
excessive nutrients in aquatic ecosystems resulting
in algal blooms and anoxia, leads
to fish kills, loss of
biodiversity, and renders water unfit for drinking and other industrial uses.
Excessive fertilization and manure application to cropland, as well as high
livestock stocking densities cause nutrient (mainlynitrogen and phosphorus) runoff and leaching from agricultural land. These nutrients
are major nonpoint pollutants contributing to eutrophication
of aquatic ecosystems.[110]
Agriculture accounts for 70
per cent of withdrawals of freshwater resources.[111] Agriculture
is a major draw on water from aquifers, and
currently draws from these underground water sources at an unsustainable rate.
It is long known that aquifers in areas as diverse as northern China, the Upper Ganges and the western US are being
depleted, and new research extends these problems to aquifers in Iran, Mexico
and Saudi Arabian.[112] Increasing
pressure is being placed on water resources by industry and urban areas,
meaning that water
scarcity is increasing and agriculture is facing the challenge
of producing more food for the world's growing population with fewer water
resources.[113] Agricultural
water usage can also cause major environmental problems, including the
destruction of natural wetlands, the spread of water-borne diseases, and land
degradation through salinization and
waterlogging, when irrigation is performed incorrectly.[114]
Pesticide use has increased
since 1950 to 2.5 million tons annually worldwide, yet crop loss from pests has
remained relatively constant.[115] The
World Health Organization estimated in 1992 that 3 million pesticide poisonings
occur annually, causing 220,000 deaths.[116] Pesticides
select for pesticide
resistance in the pest population, leading to a condition
termed the 'pesticide treadmill' in which pest resistance warrants the
development of a new pesticide.[117]
An alternative argument is
that the way to 'save the environment' and prevent famine is by using pesticides and
intensive high yield farming, a view exemplified by a quote heading the Center
for Global Food Issues website: 'Growing more per acre leaves more land for
nature'.[118][119] However,
critics argue that a trade-off between the environment and a need for food is
not inevitable,[120] and
that pesticides simply replace good agronomic practices such as crop rotation.[117]
See
also: Climate change and agriculture
Climate change has
the potential to affect agriculture through changes in temperature, rainfall
(timing and quantity), CO2, solar radiation and
the interaction of these elements.[73][121] Extreme
events, such as droughts and floods, are forecast to increase as climate change
takes hold.[122] Agriculture
is among sectors most vulnerable to the impacts of climate change; water supply
for example, will be critical to sustain agricultural production and provide
the increase in food output required to sustain the world's growing population.
Transformational approaches will be needed to manage natural resources in
future. For example, policies, practices and tools promoting climate-smart
agriculture will be important, as will better use of scientific information on
climate for assessing risks and vulnerability. Planners and policy-makers will
need to help create suitable policies that encourage funding for such
agricultural transformation.[123]
Agriculture can both
mitigate or worsen global
warming. Some of the increase in CO2 in
the atmosphere comes
from the decomposition of organic matter in
thesoil, and much of
the methane emitted
into the atmosphere is caused by the decomposition of organic matter in wet
soils such as rice
paddies,[124] as
well as the normal digestive activities of farm animals. Further, wet or anaerobic soils also lose nitrogen through denitrification,
releasing the greenhouse
gases nitric
oxideand nitrous oxide.[125] Changes
in management can reduce the release of these greenhouse gases, and soil can
further be used to sequester some of the CO2in the
atmosphere.[124]
Some major organisations
are hailing farming within agroecosystems as
the way forward for mainstream agriculture. Current farming methods have
resulted in over-stretched water resources, high levels of erosion and
reduced soil fertility.
According to a report by the International Water Management Institute andUNEP,[126] there
is not enough water to continue farming using current practices; therefore how
we use critical water, land, and ecosystem resources
to boost crop yields must be reconsidered. The report suggested that we need to
assign value to ecosystems, recognize environmental and livelihood tradeoffs,
and balance the rights of a variety of users and interests. We would also need
to address inequities that result when such measures are adopted, such as the
reallocation of water from poor to rich, the clearing of land to make way for
more productive farmland, or the preservation of a wetland system that limits
fishing rights.[127]
Technological advancements
help provide farmers with tools and resources to make farming more sustainable.[128] New
technologies have given rise to innovations like conservation tillage, a
farming process which helps prevent land loss to erosion, water pollution and
enhances carbon sequestration.[129]
Main
article: Agricultural economics
See
also: Agricultural
subsidy and Rural economics
Agricultural economics
relates to the "production, distribution and consumption of [agricultural]
goods and services".[130] National
government policies can significantly change the economic marketplace for
agricultural products, in the form of taxation, subsidies, tariffs and
other measures.[131] Since
at least the 1960s, a combination of import/export restrictions, exchange
rate policies and subsidies have affected farmers in both the
developing and developed world. In the 1980s, it was clear that non-subsidized
farmers in developing countries were experiencing adverse affects from national
policies that created artificially low global prices for farm products. Between
the mid-1980s and the early 2000s, several international agreements were put
into place that limited agricultural tariffs, subsidies and other trade
restrictions.[132]
However, as of 2009, there
was still a significant amount of policy-driven distortion in global
agricultural product prices. The three agricultural products with the greatest
amount of trade distortion were sugar, milk and rice, mainly due to taxation. Among
the oilseeds, sesame had
the greatest amount of taxation, but overall, feed grains and oilseeds had much
lower levels of taxation than livestock products. Since the 1980s,
policy-driven distortions have seen a greater decrease among livestock products
than crops during the worldwide reforms in agricultural policy.[133] Despite
this progress, certain crops, such as cotton, still see subsidies in developed
countries artificially deflating global prices, causing hardship in developing
countries with non-subsidized farmers.[134]
In the United States, food
costs attributed to food
processing, distribution, and agricultural marketing have risen while the
costs attributed to farming have declined. This is related to the greater
efficiency of farming, combined with the increased level of value addition
(e.g. more highly processed products) provided by the supply chain. From 1960
to 1980 the farm share was around 40%, but by 1990 it had declined to 30% and
by 1998, 22.2%. Market
concentration has increased in the sector as well, with the top
20 food manufacturers accounting for half the food-processing value in 1995,
over double that produced in 1954. As of 2000 the top six US supermarket groups
had 50% of sales compared to 32% in 1992. Although the total effect of the increased
market concentration is likely increased efficiency, the changes
redistribute economic
surplus from producers (farmers) and consumers, and may have
negative implications for rural communities.[135]
See
also: List of countries by GDP sector composition and List of largest producing
countries of agricultural commodities
Political world map shaded
according to the agricultural portion of GDP for each country and spanning the
years 1970–2008.. This time covers the effects of the Green Revolution.
Below is a list of
countries by agricultural output in 2011.
|
Agricultural output in 2011
|
||||
|
Rank
|
Country
|
Output in
billions ofUS$ |
Composition
of GDP (%) |
% of Global
Agricultural Output |
|
—
|
4,249.237
|
6.1%
|
100.0%
|
|
|
1
|
737.113
|
10.1%
|
17.3%
|
|
|
—
|
316.398
|
1.8%
|
7.4%
|
|
|
2
|
303.382
|
18.1%
|
7.1%
|
|
|
3
|
181.128
|
1.2%
|
4.3%
|
|
|
4
|
144.589
|
5.8%
|
3.4%
|
|
|
5
|
126.006
|
14.9%
|
3.0%
|
|
|
6
|
93.179
|
39.0%
|
2.2%
|
|
|
7
|
82.173
|
1.4%
|
1.9%
|
|
|
8
|
81.417
|
4.4%
|
1.9%
|
|
|
9
|
71.584
|
9.2%
|
1.7%
|
|
|
10
|
59.529
|
4.0%
|
1.4%
|
|
|
11
|
54.034
|
11.2%
|
1.3%
|
|
|
12
|
49.286
|
3.3%
|
1.2%
|
|
|
13
|
47.198
|
1.7%
|
1.1%
|
|
|
14
|
45.971
|
13.3%
|
1.1%
|
|
|
15
|
45.037
|
3.9%
|
1.1%
|
|
|
16
|
44.764
|
10.0%
|
1.1%
|
|
|
17
|
44.008
|
20.9%
|
1.0%
|
|
|
18
|
41.776
|
1.9%
|
1.0%
|
|
|
19
|
33.944
|
14.4%
|
0.8%
|
|
|
20
|
33.442
|
12.0%
|
0.8%
|
|
|
–
|
Remaining
Countries
|
1,933.377
|
45.5%
|
|
Since the 1940s,
agricultural productivity has increased dramatically, due largely to the
increased use of energy-intensive mechanization, fertilizers andpesticides. The vast
majority of this energy input comes from fossil fuel sources.[136] Between
the 1960–65 measuring cycle and the cycle from 1986–90, theGreen Revolution transformed
agriculture around the globe, with world grain production increasing
significantly (between 70% and 390% for wheat and 60% to 150% for rice,
depending on geographic area)[137] as world population doubled.
Modern agriculture's heavy reliance on petrochemicals and mechanization has
raised concerns that oil shortages could increase costs and reduce agricultural
output, causing food shortages.[138]
|
Agriculture and food system share (%) of total energy
consumption by three industrialized nations |
|||
|
Country
|
Year
|
Agriculture
(direct & indirect) |
Food
system |
|
United
Kingdom[139]
|
2005
|
1.9
|
11
|
|
United
States[140]
|
1996
|
2.1
|
10
|
|
United
States[141]
|
2002
|
2.0
|
14
|
|
Sweden[142]
|
2000
|
2.5
|
13
|
Modern or industrialized
agriculture is dependent on fossil fuels in two fundamental ways: 1) direct
consumption on the farm and 2) indirect consumption to manufacture inputs used
on the farm. Direct consumption includes the use of lubricants and fuels to operate
farm vehicles and machinery; and use of gas, liquid propane, and electricity to
power dryers, pumps, lights, heaters, and coolers. American farms directly
consumed about 1.2 exajoules (1.1 quadrillion BTU) in 2002, or just over 1
percent of the nation's total energy.[138]
Indirect consumption is
mainly oil and natural gas used to manufacture fertilizers and pesticides,
which accounted for 0.6 exajoules (0.6 quadrillion BTU) in 2002.[138] The
natural gas and coal consumed by the production of nitrogen
fertilizer can account for over half of the agricultural energy
usage. China utilizes mostly coal in the production of nitrogen fertilizer,
while most of Europe uses large amounts of natural gas and small amounts of
coal. According to a 2010 report published by The Royal Society,
agriculture is increasingly dependent on the direct and indirect input of
fossil fuels. Overall, the fuels used in agriculture vary based on several
factors, including crop, production system and location.[143] The
energy used to manufacture farm machinery is also a form of indirect
agricultural energy consumption. Together, direct and indirect consumption by
US farms accounts for about 2 percent of the nation's energy use. Direct and
indirect energy consumption by U.S. farms peaked in 1979, and has gradually
declined over the past 30 years.[138] Food systems encompass
not just agricultural production, but also off-farm processing, packaging,
transporting, marketing, consumption, and disposal of food and food-related
items. Agriculture accounts for less than one-fifth of food system energy use
in the US.[140][141]
In 2007, higher incentives
for farmers to grow non-food biofuel crops[144] combined
with other factors, such as overdevelopment of former farm lands, rising
transportation costs, climate
change, growing consumer demand in China and India, and population growth,[145] caused food shortages in
Asia, the Middle East, Africa, and Mexico, as well as rising food prices around
the globe.[146][147] 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.[49][50][51]
M. King Hubbert's
prediction of world petroleum production rates. Modern agriculture is totally
reliant on petroleum energy.[148]
In the event of a petroleum
shortage (see peak oil for
global concerns), organic
agriculture can be more attractive than conventional practices
that use petroleum-based pesticides, herbicides, or fertilizers. Some studies
using modern organic-farming methods have reported yields as high as those
available from conventional farming.[149] In
the aftermath of the fall of the Soviet Union, with shortages of
conventional petroleum-based inputs, Cuba made use of mostly-organic practices,
including biopesticides,
plant-based pesticides and sustainable cropping practices, to feed its
populace.[150] However,
organic farming may be more labor-intensive
and would require a shift of the workforce from urban to rural areas.[151] The
reconditioning of soil to restore nutrients lost during the use of monoculture agriculture
techniques also takes time.[149]
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
might just provide enough fuel for a new organic-agriculture fusion.[152][153]
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.[154] The
possibility of success of these programs is questioned by ecologists and
economists concerned with unsustainable GMO practices such as terminator seeds.[155][156]
While there has been some
research on sustainability using GMO crops, at least one prominent multi-year
attempt by Monsanto
Company has been unsuccessful, though during the same period
traditional breeding techniques yielded a more sustainable variety of the same
crop.[157]
Main
article: Agricultural
policy
Agricultural
policy is the set of government decisions and actions relating
to domestic agriculture and imports of foreign agricultural products.
Governments usually implement agricultural policies with the goal of achieving
a specific outcome in the domestic agricultural product markets. Some
overarching themes include risk management and adjustment (including policies
related to climate change, food safety and
natural disasters), economic
stability (including policies related to taxes), natural
resources and environmental sustainability (especially water
policy), research and development, and market access for domestic commodities
(including relations with global organizations and agreements with other
countries).[158] Agricultural
policy can also touch on food quality,
ensuring that the food supply is of a consistent and known quality, food security,
ensuring that the food supply meets the population's needs, and conservation.
Policy programs can range from financial programs, such as subsidies, to
encouraging producers to enroll in voluntary quality assurance programs.[159]
 |
Main
article: Outline of agriculture
 |
·
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