![Contour line 8 gener 2007](https://upload.wikimedia.org/wikipedia/commons/8/83/Contour_line_8_gener_2007.jpg)
Contour bunding or contour farming or Contour ploughing is the
farming
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...
practice of
plowing
A plough or plow ( US; both ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms are drawn by tractors. A plough may have a wooden, iron or ...
and/or planting across a slope following its elevation
contour line
A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional grap ...
s. These contour lines create a water break which reduces the formation of rills and gullies during times of heavy precipitation, allowing more time for the water to settle into the soil. In contour plowing, the ruts made by the plow run perpendicular rather than parallel to the slopes, generally furrows that curve around the land and are level. This method is also known for preventing tillage erosion.
Tillage
Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoein ...
erosion is the soil movement and erosion by tilling a given plot of land. A similar practice is contour bunding where stones are placed around the contours of slopes. Contour ploughing helps to reduce
soil erosion
Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and ...
.
Soil erosion prevention practices such as this can drastically decrease negative effects associated with soil erosion such as reduced crop productivity, worsened water quality, lower effective reservoir water levels, flooding, and
habitat destruction
Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
. Contour farming is considered an active form of
sustainable agriculture
Sustainable agriculture is farming in sustainable ways meeting society's present food and textile needs, without compromising the ability for current or future generations to meet their needs. It can be based on an understanding of ecosystem ser ...
.
History
The
Phoenicians
Phoenicia () was an ancient Semitic-speaking peoples, ancient thalassocracy, thalassocratic civilization originating in the Levant region of the eastern Mediterranean, primarily located in modern Lebanon. The territory of the Phoenician city-st ...
first developed the practice of contour farming and spread it throughout the
Mediterranean
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...
. However, the Romans preferred cultivation in straight furrows and this practice became standard.
Modern history
This was one of the main procedures promoted by the US Soil Conservation Service (the current
Natural Resources Conservation Service
Natural Resources Conservation Service (NRCS), formerly known as the Soil Conservation Service (SCS), is an agency of the United States Department of Agriculture (USDA) that provides technical assistance to farmers and other private landowners an ...
) during the 1930s. The
US Department of Agriculture
The United States Department of Agriculture (USDA) is the United States federal executive departments, federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, ...
established the Soil Conservation Service in 1935 during the
Dust Bowl
The Dust Bowl was a period of severe dust storms that greatly damaged the ecology and agriculture of the American and Canadian prairies during the 1930s. The phenomenon was caused by a combination of both natural factors (severe drought) an ...
when it became apparent that soil erosion was a huge problem along with
desertification
Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid. It is the spread of arid areas caused by ...
.
The extent of the problem was such that the 1934 "Yearbook of Agriculture" noted that ''Approximately 35 million acres
42,000 km²of formerly cultivated land have essentially been destroyed for crop production. . . . 100 million acres
05,000 km²now in crops have lost all or most of the topsoil; 125 million acres
06,000 km²of land now in crops are rapidly losing topsoil.'' This can lead to large scale
desertification
Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid. It is the spread of arid areas caused by ...
which can permanently transform a formerly productive landscape to an arid one that becomes increasingly intensive and expensive to farm.
The Soil Conservation Service worked with state governments and universities with established agriculture programs such as the
University of Nebraska
A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, the ...
to promote the method to farmers. By 1938, the introduction of new agricultural techniques such as contour plowing had reduced the loss of soil by 65% despite the continuation of the drought.
Demonstrations showed that contour farming, under ideal conditions, will increase yields of row crops by up to 50%, with increases of between 5 and 10% being common. Importantly, the technique also significantly reduces soil erosion, fertilizer loss, and overall makes farming less energy and resource intensive under most circumstances. Reducing fertilizer loss not only saves the farmer time and money, but it also decreases risk of harming regional freshwater systems. Soil erosion caused from heavy rain can encourage the development of rills and gullies which carry excess nutrients into freshwater systems through the process of
eutrophication
Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...
Contour plowing is also promoted in countries with similar rainfall patterns to the United States such as western
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
and
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
.
The practice is effective only on slopes with between 2% and 10% gradient and when rainfall does not exceed a certain amount within a certain period. On steeper slopes and areas with greater rainfall, a procedure known as
strip cropping
Strip cropping is a method of farming which involves cultivating a field partitioned into long, narrow strips which are alternated in a crop rotation system. It is used when a slope is too steep or when there is no alternative method of preventin ...
is used with contour farming to provide additional protection. Contour farming is most effective when used with other soil conservation methods like
strip cropping
Strip cropping is a method of farming which involves cultivating a field partitioned into long, narrow strips which are alternated in a crop rotation system. It is used when a slope is too steep or when there is no alternative method of preventin ...
,
terrace farming, and the use of
cover crop
In agriculture, cover crops are plants that are planted to cover the soil rather than for the purpose of being harvested. Cover crops manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife i ...
s. The proper combination of such farming methods can be determined by various climatic and soil conditions of that given area. Farming sites are often classified into five levels: insensitive, mild, moderate, high and extreme, depending on the regions soil sensitivity. Contour farming is applied in certain European countries such as Belgium, Italy, Greece, Romania, Slovenia and Spain in areas with higher than 10% slope.
P. A. Yeomans'
Keyline Design
Keyline design is a landscaping technique of maximizing the beneficial use of the water resources of a tract of land. The "keyline" is a specific topographic feature related to the natural flow of water on the tract. Keyline design is a system o ...
system is critical of traditional contour plowing techniques, and improves the system through observing normal land form and
topography
Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps.
Topography is a field of geoscience and planetary sci ...
. At one end of a contour the slope of the land will always be steeper than at the other. Thus when plowing parallel runs paralleling any contour the plow furrows soon deviate from a true contour. Rain water in these furrows will thus flow sideways along the falling "contour" line. This can often concentrate water in a ways that exacerbates erosion instead of reducing it. Yeomans was the first to appreciate the significance of this phenomenon. Keyline cultivation utilizes this "off contour" drift in cultivating furrows to control the movement of rain water for the benefit of the land. ( See Chapter 7 in
Priority One
Prioritization is an action that arranges items or activities in order of importance.
Priority may refer specifically to:
Law
* Priority or right of way on the road, see Traffic § Priority (right of way)
** Priority signs, a traffic sign that ...
History of Twentieth Century Soil Conservation and Keyline.)
Contour bunding has been widely adopted in
Burkina Faso
Burkina Faso (, ; , ff, 𞤄𞤵𞤪𞤳𞤭𞤲𞤢 𞤊𞤢𞤧𞤮, italic=no) is a landlocked country in West Africa with an area of , bordered by Mali to the northwest, Niger to the northeast, Benin to the southeast, Togo and Ghana to the ...
after it was suggested by British
Oxfam
Oxfam is a British-founded confederation of 21 independent charitable organizations focusing on the alleviation of global poverty, founded in 1942 and led by Oxfam International.
History
Founded at 17 Broad Street, Oxford, as the Oxford Co ...
worker
Bill Hereford
Bill(s) may refer to:
Common meanings
* Banknote, paper cash (especially in the United States)
* Bill (law), a proposed law put before a legislature
* Invoice, commercial document issued by a seller to a buyer
* Bill, a bird or animal's beak
Plac ...
in the beginning of the 1980s.
See also
*
George Washington Carver
George Washington Carver ( 1864 – January 5, 1943) was an American agricultural scientist and inventor who promoted alternative crops to cotton and methods to prevent soil depletion. He was one of the most prominent black scientists of the ea ...
*
Soil conservation
Soil conservation is the prevention of loss of the topmost layer of the soil from erosion or prevention of reduced fertility caused by over usage, acidification, salinization or other chemical soil contamination.
Slash-and-burn and other unsust ...
*
Tillage erosion
Tillage erosion is a form of soil erosion occurring in cultivated fields due to the movement of soil by tillage. There is growing evidence that tillage erosion is a major soil erosion process in agricultural lands, surpassing water and wind erosion ...
References
External links
NRCS Conservation Practice Standard 330-Contour Farming''4 page pdf file''
American Experience page on the dust bowlEncyclopædia Britannica page on contour farmingNatural Resources Conservation Service page on sustainable farming*
Pearce, F. (2002) Africans go back to the land as plants reclaim the desert,
New Scientist
''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publishe ...
21. September, page 4.
Looking after our land - Soil and Water Conservation in Dryland Africa- Detailed instructions for contour bund construction.
BBC News - Sahara desert frontiers turn greenArticle on Water Erosion from Penn State College of Agricultural Sciences
Article on Tillage Erosion from Penn State College of Agricultural Sciences
{{Use dmy dates, date=April 2017
Agricultural soil science