Shifting cultivation

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Shifting cultivation


Shifting cultivation refers to a practice whereby a tract of land is alternately used for crop production and then allowed to return to native vegetation for a period of years. Typically, the land is cleared of vegetation, crops are grown for two or three years, and then the land abandoned for a period of 10 or more years. To facilitate land clearing prior to cultivation, the vegetation is cut and the debris burned. The practice is also called slash-and-burn agriculture or swidden agriculture.

Shifting cultivation is most common in the tropics where farming techniques are less technologically advanced. The soils are usually low in plant nutrients. For two or three years following land clearing, the nutrients brought to, or near, the soil surface by deep rooting trees, shrubs, and other plants support cultivated crops. With native management, the available nutrients are removed by the cultivated crops or leached so that after a few years the soil will support only minimal plant growth. It is then allowed to return to native vegetation which slowly concentrates the nutrients in the surface soil again. After a period of years the cycle repeats. Erosion is often severe on sloping land during the cultivated phase. On some soils, particularly in the tropics, the soil structure becomes massive and hard.

See also Leaching; Soil compaction; Soil organic matter

[William E. Larson ]


RESOURCES

BOOKS

Ramakrishnan, P. S. Shifting Agriculture and Sustainable Development: An Interdisciplinary Study from North-Eastern India. Park Ridge, NJ: Parthenon Publishing Group, 1992.

Vasey, D. E. An Ecological History of Agriculture. Ames, IA: Iowa State University Press, 1992.

PERIODICALS

Monastersky, R. "Legacy of Fire: The Soil Strikes Back." Science News 133 (April 9, 1988): 231.

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shifting cultivation (slash-and-burn agriculture) The traditional agricultural system of semi-nomadic people, in which a small area of forest is cleared by burning, cultivated for 1–5 years, and then abandoned as soil fertility and crop yields fall and weeds encroach. Ideally vegetation succession subsequently returns the plot to climax woodland, and soil fertility is gradually restored. Shifting cultivation of this type was once practised world-wide but in modern times it has been primarily associated with tropical rain-forest areas. The system is best suited to low population densities. With increasing population pressure, abandoned plots are often cleared again before a full climax community has been restored, leading eventually to nutrient depletions of the system and degradation of forest to open savannah-type woodland, or scrub.

views updated

shifting cultivation(slash-and-burn agriculture) The traditional agricultural system of semi-nomadic people, in which a small area of forest is cleared by burning, cultivated for 1–5 years, and then abandoned as soil fertility and crop yields fall and weeds encroach. Ideally vegetation succession subsequently returns the plot to climax woodland, and soil fertility is gradually restored. Shifting cultivation of this type was once practised worldwide but in modern times it has been primarily associated with tropical rain-forest areas. The system is best suited to low population densities. With increasing population pressure, abandoned plots are often cleared again before a full climax community has been restored, leading eventually to nutrient depletion of the system and degradation of forest to open savannah-type woodland or scrub.