Contour plowing
Encyclopedia
Contour line
A contour line of a function of two variables is a curve along which the function has a constant value. In cartography, a contour line joins points of equal elevation above a given level, such as mean sea level...
s. The rows formed slow water run-off during rainstorms to prevent soil erosion and allow the water time to settle into the soil. In contour plowing, the ruts made by the plow run perpendicular rather than parallel to slopes, generally resulting in furrows that curve around the land and are level. A similar practice is contour bunding
Bunding
Bunding, also called a bund wall, is the area within a structure designed to prevent inundation or breaches of various types.-Liquid containment:...
where stones are placed around the contours of slopes.
History
The Phoenicians first developed the practice of contour farming and spread it throughout the Mediterranean. However, the Romans preferred cultivation in straight furrows and this practice became standard in Europe and Britain.Modern history
This was one of the main procedures promoted by the U.S. Soil Conservation Service (the current Natural Resources Conservation ServiceNatural Resources Conservation Service
The Natural Resources Conservation Service , formerly known as the Soil Conservation Service , is an agency of the United States Department of Agriculture that provides technical assistance to farmers and other private landowners and managers.Its name was changed in 1994 during the Presidency of...
) during the 1930s. The U.S. Department of Agriculture established the Soil Conservation Service in 1935 during the dust bowl
Dust Bowl
The Dust Bowl, or the Dirty Thirties, was a period of severe dust storms causing major ecological and agricultural damage to American and Canadian prairie lands from 1930 to 1936...
when it became apparent that soil erosion was a huge problem.
The extent of the problem was such that the 1934 "Yearbook of Agriculture" noted that Approximately 35 million acres [142,000 km²] of formerly cultivated land have essentially been destroyed for crop production. . . . 100 million acres [405,000 km²] now in crops have lost all or most of the topsoil; 125 million acres [506,000 km²] of land now in crops are rapidly losing topsoil.
The Soil Conservation Service worked with state governments and universities with established agriculture programs such as the University of Nebraska 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.
Contour plowing is also promoted in countries with similar rainfall patterns to the United States such as western Canada and Australia.
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 is used with contour farming to provide additional protection.
P. A. Yeomans
P. A. Yeomans
Percival Alfred Yeomans was an Australian inventor known for the Keyline system for the development of land and increasing the fertility of that land. As a mining engineer and gold assayer, Yeomans had developed a keen sense of hydrology and equipment design...
' Keyline Design
Keyline Design
Keyline design is a technique for maximizing beneficial use of water resources of a piece of land. The Keyline refers to a specific topographic feature linked to water flow...
system is critical of traditional contour plowing techniques, and improves the system through observing normal land form and topography
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
. 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 History of Twentieth Century Soil Conservation and Keyline.)
Contour bunding has been widely adopted in Burkina Faso
Burkina Faso
Burkina Faso – also known by its short-form name Burkina – is a landlocked country in west Africa. It is surrounded by six countries: Mali to the north, Niger to the east, Benin to the southeast, Togo and Ghana to the south, and Côte d'Ivoire to the southwest.Its size is with an estimated...
after it was suggested by British Oxfam
Oxfam
Oxfam is an international confederation of 15 organizations working in 98 countries worldwide to find lasting solutions to poverty and related injustice around the world. In all Oxfam’s actions, the ultimate goal is to enable people to exercise their rights and manage their own lives...
worker Bill Hereford in the beginning of the 1980s.
External links
- NRCS Conservation Practice Standard 330-Contour Farming 4 page pdf file
- American Experience page on the dust bowl
- Encyclopaedia Britannica page on contour farming
- Purdue University article on contour farming
- Natural Resources Conservation Service page on sustainable farming
- Manitoba Soil Conservation Resource Manual
- Priority One. Together We Can Beat Global Warming
- Pearce, F.Fred PearceFred Pearce is an English author and journalist based in London. He has been described as one of Britain's finest science writers and has reported on environment, popular science and development issues from 64 countries over the past 20 years. He specializes in global environmental issues,...
(2002) Africans go back to the land as plants reclaim the desert, New ScientistNew ScientistNew Scientist is a weekly non-peer-reviewed English-language international science magazine, which since 1996 has also run a website, covering recent developments in science and technology for a general audience. Founded in 1956, it is published by Reed Business Information Ltd, a subsidiary of...
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 green