Sustainable agriculture
From Wikipedia, the free encyclopedia
Sustainable agriculture is the act of farming using principles of ecology, the study of relationships between organisms
and their environment. The phrase was reportedly coined by Australian
agricultural scientist Gordon McClymont.[1] It has been defined as "an integrated
system of plant and animal production practices having a site-specific
application that will last over the long term" For Example:
·
Enhance environmental
quality and the natural resource base upon which the agricultural economy
depends
·
Make the most
efficient use of non-renewable resources and on-farm resources and integrate, where appropriate, natural
biological cycles and controls
·
Sustain the economic
viability of farm operations
Contents
Farming and natural resources
Sustainable
agriculture can be understood as an ecosystem approach to agriculture.[3] Practices that can cause long-term damage to
soil include excessive tilling of the soil(leading to erosion) and irrigation without adequate drainage (leading to salinization). Long-term experiments have provided some of the best data on how various practices
affect soil properties essential to sustainability. In the United States a
federal agency, USDA-Natural Resources Conservation Service, specializes in
providing technical and financial assistance for those interested in pursuing
natural resource conservation and production agriculture as compatible goals.
The
most important factors for an individual site are sun, air, soil, nutrients,
and water. Of the five, water and soil quality and quantity are most amenable to human intervention
through time and labor.
Although air and sunlight are available
everywhere on Earth, crops also depend on soil nutrients and the availability of water. When farmers grow and harvest crops, they remove some of these nutrients
from the soil. Without replenishment, land suffers from nutrient depletion and
becomes either unusable or suffers from reducedyields. Sustainable agriculture depends on
replenishing the soil while minimizing the use or need of non-renewable
resources, such as natural gas (used in converting
atmospheric nitrogen into synthetic fertilizer), or mineral ores (e.g.,
phosphate). Possible sources of nitrogen that would, in principle, be available
indefinitely, include:
2.
growing legume crops and forages such as peanuts or alfalfa that form symbioses
with nitrogen-fixing bacteria called rhizobia
3.
industrial production
of nitrogen by the Haber Process uses hydrogen, which is currently derived from natural gas, (but
this hydrogen could instead be made by electrolysis of water using electricity (perhaps from solar
cells or windmills)) or
4.
genetically
engineering (non-legume) crops to form nitrogen-fixing symbioses or fix
nitrogen without microbial symbionts.
The
last option was proposed in the 1970s, but is only recently becoming feasible.[4][5] Sustainable options for replacing other
nutrient inputs (phosphorus, potassium, etc.) are more limited.
More
realistic, and often overlooked, options include long-term crop rotations, returning to natural cycles that annually flood cultivated lands
(returning lost nutrients indefinitely) such as the Flooding of the Nile, the long-term use of biochar, and use of
crop and livestock landraces that are adapted to
less than ideal conditions such as pests, drought, or lack of nutrients.
Crops
that require high levels of soil nutrients can be cultivated in a more
sustainable manner if certain fertilizer management practices are adhered to.
Water
In
some areas sufficient rainfall is available for crop growth, but many other
areas require irrigation. For irrigation systems to be sustainable, they
require proper management (to avoid salinization) and must not use more water
from their source than is naturally replenishable. Otherwise, the water source
effectively becomes a non-renewable resource. Improvements in water well
drilling technology and submersible pumps, combined with the development of drip irrigation and low pressure pivots, have made it possible
to regularly achieve high crop yields in areas where reliance on rainfall alone
had previously made successful agriculture unpredictable. However, this
progress has come at a price. In many areas, such as the Ogallala Aquifer, the water is being used faster than it can
be recharged.
Several
steps must be taken to develop drought-resistant farming systems even in
"normal" years with average rainfall. These measures include both
policy and management actions: 1) improving water conservation and storage
measures, 2) providing incentives for selection of drought-tolerant crop
species, 3) using reduced-volume irrigation systems, 4) managing crops to
reduce water loss, or 5) not planting crops at all.[6]
Indicators
for sustainable water resource development are:
¤
Internal renewable water resources. This is the average annual flow of rivers
and groundwater generated from endogenous precipitation, after ensuring that
there is no double counting. It represents the maximum amount of water resource
produced within the boundaries of a country. This value, which is expressed as
an average on a yearly basis, is invariant in time (except in the case of
proved climate change). The indicator can be expressed in three different
units: in absolute terms (km3/yr), in mm/yr (it is a measure of the humidity of
the country), and as a function of population (m3/person per yr).
¤
Global renewable water resources. This is the sum of internal renewable water
resources and incoming flow originating outside the country. Unlike internal
resources, this value can vary with time if upstream development reduces water
availability at the border. Treaties ensuring a specific flow to be reserved
from upstream to downstream countries may be taken into account in the
computation of global water resources in both countries.
¤
Dependency ratio. This is the proportion of the global renewable water
resources originating outside the country, expressed in percentage. It is an
expression of the level to which the water resources of a country depend on
neighbouring countries.
¤
Water withdrawal. In view of the limitations described above, only gross water
withdrawal can be computed systematically on a country basis as a measure of
water use. Absolute or per-person value of yearly water withdrawal gives a
measure of the importance of water in the country's economy. When expressed in
percentage of water resources, it shows the degree of pressure on water
resources. A rough estimate shows that if water withdrawal exceeds a quarter of
global renewable water resources of a country, water can be considered a
limiting factor to development and, reciprocally, the pressure on water
resources can have a direct impact on all sectors, from agriculture to
environment and fisheries.[7]
Soil
Soil erosion is fast becoming one of the worlds greatest
problems. It is estimated that "more than a thousand million tonnes of
southern Africa's soil are eroded every year. Experts predict that crop yields
will be halved within thirty to fifty years if erosion continues at present
rates."[8] Soil erosion is not unique to Africa but is
occurring worldwide. The phenomenon is being calledPeak Soil as present large scale factory farming
techniques are jeopardizing humanity's ability to grow food in the present and
in the future.[9] Without efforts to improve soil management
practices, the availability of arable soil will become increasingly
problematic.[10]
Some
Soil Management techniques
6.
Protecting soil from
water run off(soil erosion)
Phosphate
Phosphate
is a primary component in the chemical fertilizer which is applied in modern
agricultural production. However, scientists estimate that rock phosphate
reserves will be depleted in 50–100 years and that Peak phosphorus will occur in about 2030.[11] The phenomenon of Peak phosphorus is expected to increase food prices as
fertilizer costs increase as rock phosphate reserves become more difficult to
extract. In the long term, phosphate will therefore have to be recovered and
recycled from human and animal waste in order to maintain food production.
Land
As
the global population increases and demand for food increases, there is
pressure on land resources. Land can also be considered a finite resource on
Earth. Expansion of agricultural land has an impact on biodiversity and contributes to deforestation. The Food and Agriculture Organisation of the United Nations estimates that in coming
decades, cropland will continue to be lost to industrial and urban development,
along with reclamation of wetlands, and conversion of forest to cultivation,
resulting in the loss of biodiversity and increased soil erosion.[12]
Energy for Agriculture
Energy
is used all the way down the food chain from farm to fork. In industrial
agriculture, energy is used in on-farm mechanisation, food processing, storage,
and transportation processes.[13] It has therefore been found that energy prices
are closely linked to food prices.[14] Oil is also used as an input in agricultural
chemicals. Higher prices of non-renewable energy resources are projected by the International Energy Agency. Increased energy prices as a result of fossil fuel resources
being depleted may therefore impact negatively on the global food security
unless action is taken to 'decouple' fossil fuel energy from food production, with
a move towards 'Energy-Smart' agricultural systems.[14]
Economics
Socioeconomic
aspects of sustainability are also partly understood. Regarding less
concentrated farming, the best known analysis is Netting's study on smallholder
systems through history.[15] The Oxford Sustainable Group defines sustainability in this context in a much broader form,
considering effect on all stakeholders in a 360 degree approach
Given
the finite supply of natural resources at any specific cost and location, agriculture
that is inefficient or damaging to needed resources may eventually exhaust the
available resources or the ability to afford and acquire them. It may also generate
negative externality,
such as pollution as well as financial and production costs.
The
way that crops are sold must be accounted for
in the sustainability equation. Food sold locally does not require additional energy for
transportation (including consumers). Food sold at a remote location, whether
at a farmers' market or the supermarket, incurs a different set of energy cost for
materials, labour,
andtransport.
Methods
What
grows where and how it is grown are a matter of choice. Two of the many
possible practices of sustainable agriculture are crop rotation and soil amendment, both designed to ensure that crops being
cultivated can obtain the necessary nutrients for healthy growth. Soil amendments would include
using locally available compost from community recycling centers. These
community recycling centers help produce the compost needed by the local
organic farms.
Many
scientists, farmers, and businesses have debated how to make agriculture
sustainable. Using community recycling from yard and kitchen waste utilizes a
local area's commonly available resources. These resources in the past were
thrown away into large waste disposal sites, are now used to produce low cost
organic compost for organic farming. Other practices includes growing a diverse
number of perennial crops in a single field, each of which would grow in
separate season so as not to compete with each other for natural resources.[16] This system would result in increased
resistance to diseases and decreased effects of erosion and loss of nutrients
in soil. Nitrogen fixation from legumes, for example, used in conjunction
with plants that rely on nitrate from soil for growth, helps to allow the land
to be reused annually. Legumes will grow for a season and replenish the soil
with ammonium and nitrate, and the next season other plants can be seeded and
grown in the field in preparation for harvest.
Monoculture, a method of growing only one crop at a time
in a given field, is a very widespread practice, but there are questions about
its sustainability, especially if the same crop is grown every year. Today it
is realized to get around this problem local cities and farms can work together
to produce the needed compost for the farmers around them. This combined with
growing a mixture of crops (polyculture)
sometimes reduces disease or pest problems [17] but polyculture has rarely, if ever, been
compared to the more widespread practice of growing different crops in
successive years (crop rotation) with the same overall crop diversity. Cropping systems that include a variety of
crops (polyculture and/or rotation) may also replenish nitrogen (if legumes are included) and may also use resources such
as sunlight, water, or nutrients more efficiently (Field Crops Res. 34:239).
Replacing
a natural ecosystem with a few specifically chosen plant varieties reduces the
genetic diversity found in wildlife and makes the organisms susceptible to
widespread disease.
The Great Irish Famine (1845–1849) is a well-known example of the dangers of monoculture. In practice, there is no single approach to
sustainable agriculture, as the precise goals and methods must be adapted to
each individual case. There may be some techniques of farming that are
inherently in conflict with the concept of sustainability, but there is widespread
misunderstanding on impacts of some practices. Today the growth of local
farmers' markets offer small farms the ability to sell the products that they
have grown back to the cities that they got the recycled compost from. By using
local recycling this will help move people away from the slash-and-burn techniques that are the characteristic feature
of shifting cultivators are often cited as inherently destructive, yet slash-and-burn
cultivation has been practiced in the Amazon for at least 6000 years;[18] serious deforestation did not begin until the
1970s, largely as the result of Brazilian government programs and policies.[19] To note that it may not have been slash-and-burn
so much asslash-and-char, which with the addition of organic matter produces terra preta, one of the richest soils on Earth and the
only one that regenerates itself.
There
are also many ways to practice sustainable animal husbandry. Some of the key
tools to grazing management include fencing off the grazing area into smaller
areas called paddocks,
lowering stock density, and moving the stock between paddocks frequently.[20]
Several
attempts have been made to produce an artificial meat, using isolated tissues
to produce it in vitro; Jason Matheny's work on this topic, which in the New Harvest project, is one of the most commented.[21]
Soil treatment
Soil steaming can be used as an ecological alternative to chemicals for soil
sterilization. Different methods are available to induce steam into the soil in
order to kill pests and increase soil health. Community and farm composting of
kitchen, yard, and farm organic waste can provide most if not all the required
needs of local farms. This composting could potentially be a reliable source of
energy.
Off-farm impacts
A
farm that is able to "produce perpetually", yet has negative effects
on environmental quality elsewhere is not sustainable agriculture. An example
of a case in which a global view may be warranted is over-application of
synthetic fertilizer or animalmanures, which can improve productivity of a farm but can pollute
nearby rivers and coastal waters (eutrophication). The
other extreme can also be undesirable, as the problem of low crop yields due to
exhaustion of nutrients in the soil has been related to rainforest destruction, as in the case of slash and burn farming for livestock feed.In Asia, specific
land for sustainable farming is about 12.5 acres which includes land for animal
fodder, cereals productions lands for some cash crops and even recycling of
related food crops.In some cases even a small unit of aquaculture is also
included in this number (AARI-1996)
Sustainability
affects overall production, which must increase to meet the increasing food and
fiber requirements as the world's human population expands to a projected 9.3
billion people by 2050. Increased production may come from creating
new farmland, which may ameliorate carbon dioxide
emissions if done through reclamation of desert as in Israel and Palestine,
or may worsen emissions if done through slash and burn farming, as in Brazil.
International policy
Sustainable
agriculture has become a topic of interest in the international policy arena,
especially with regards to its potential to reduce the risks associated with a
changing climate and growing human population.
The Commission on
Sustainable Agriculture and Climate Change, as part of its recommendations for policy makers on achieving
food security in the face of climate change, urged that sustainable agriculture
must be integrated into national and international policy. The Commission
stressed that increasing weather variability and climate shocks will negatively
affect agricultural yields, necessitating early action to drive change in
agricultural production systems towards increasing resilience. It also called
for dramatically increased investments in sustainable agriculture in the next
decade, including in national research and development budgets, land
rehabilitation, economic incentives, and infrastructure improvement.[22]
Urban planning
There
has been considerable debate about which form of human residential habitat may
be a better social form for sustainable agriculture.
Many
environmentalists advocate urban developments with high population density as a
way of preserving agricultural land and maximizing energy efficiency. However,
others have theorized that sustainable ecocities,
or ecovillages which combine habitation and farming with
close proximity between producers and consumers, may provide greater
sustainability[citation needed].
The
use of available city space (e.g., rooftop gardens, community gardens, garden sharing, and other forms of urban agriculture) for cooperative food production is another
way to achieve greater sustainability[citation needed].
One
of the latest ideas in achieving sustainable agriculture involves shifting the
production of food plants from major factory farming operations to large,
urban, technical facilities called vertical farms. The advantages of vertical farming include year-round production, isolation from
pests and diseases, controllable resource recycling, and on-site production
that reduces transportation costs[citation needed]. While a vertical farm has
yet to become a reality, the idea is gaining momentum among those who believe
that current sustainable farming methods will be insufficient to provide for a
growing global population.[23]
Criticism
Efforts
toward more sustainable agriculture are supported in the sustainability
community, however, these are often viewed only as incremental steps and not as
an end. Some foresee a true sustainable steady state economy that may be very different from today's: greatly reduced energy
usage, minimal ecological footprint, fewer consumer packaged goods, local purchasing with short food supply chains, little processed foods, more home and community gardens, etc.[24][25][26]Agriculture would be very different in this
type of sustainable economy.
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