chernozem

A very black topsoil, rich in humus, typical of cool to temperate semiarid regions, such as the grasslands of European Russia.

[Russian chernozëm : chërnyĭ, black + Old Russian zemĭ, earth.]

A zonal soil with a deep A horizon, rich in humus from decomposed grass, and dark in colour.

Also known as black earths, chernozems develop on mid-latitude continental interiors where grassland is, or was, the natural vegetation.

Chernozem development is associated with temperate continental climates which have marked wet and dry seasons. There is sufficient moisture to permit the decay of the grass litter into humus, but not enough for leaching to be significant. The B horizon is lighter brown, but is often absent. The lower horizons are often rich in calcium compounds. In US soil classification chernozems fall into the category of mollisols, sub-order boroll.

The black earths, or mollisols (Seventh Approximation), are the richest soils on the planet. Known as chernozems in the Russian language (chernaya, meaning "black," and zemlya, meaning "earth"), they are found in semiarid grasslands, or steppes, which are wedged between arid deserts and humid forests. In the Soviet successor states, black earths stretch west to east from Moldavia and Volyno-Podolia in western Ukraine to the Russian North Caucasus and deep into Siberia as a steadily narrowing wedge to Irkutsk near Lake Baikal. Transitional between areas with a soil moisture surplus (forests) and areas with a conspicuous soil moisture deficit (deserts), grassland soils are only slightly leached during sporadic thunderstorms. The relative lack of precipitation ensures that solubles like calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg) are accessible to the uppermost humus layer (horizon) of the soil. The A-horizon consists of grass litter and extensive root systems that draw on a thick black to chestnut-brown humus zone that is rich in ionized colloids and natural fertility. The underlying B-horizon often possesses nodules of calcium carbonate, which during frequent droughts rises to the A-horizon through capillary action. Windblown silts known as loess further enrich chernozems by imparting a loamy soil texture.

Chernozems form in areas of cold winters and hot summers that are conducive to rapid evaporation. The resultant imbalance encourages the capillary rise of soluble nutrients from the B- to the A-horizon. Grasses thrive in these conditions, but their matted root systems create a sod that could not be breached by early wooden plows. Accordingly, until the invention of the steel-tipped plow in the 1800s, settlers considered grasslands useless. Requiring irrigation, the black earths now make up the great commercial grain belts.

Bibliography

Strahler, Arthur N. (1969). Physical Geography, 3rd ed. New York: Wiley.

—VICTOR L. MOTE

Chernozem field in Black Dirt Region of Orange County, NY, USA

Chernozem (Ukrainian: Чорнозем, Russian: чернозём, black soil), also known as "black land"^[1] or "black earth", is a black-coloured soil containing a very high percentage of humus^[2] — 3% to 15%, and high percentages of phosphoric acids, phosphorus and ammonia. Chernozem is very fertile and produces a high agricultural yield.

There are two "Chernozem belts" in the world: from Northeast Ukraine across the Black Earth Region and Southern Russia into Siberia, and in the Canadian Prairies. Similar soil types occur in Texas. It has a large depth, often more than 40 inches (1 m) and up to 250 inches (6 metres) in Ukraine. The terrain can also be found in small quantities elsewhere (for example, on 1% of Polish territory). It also exists in Northeast China, near Harbin.

Chernozemic soils are a soil type in the Canadian system of soil classification and the United Nations' FAO soil classification.

Chernozemic soil type equivalents, in Canadian, FAO, and USA soil taxonomy. Source: Pedosphere.com.

Canadian	FAO	United States
Chernozemic	Kastanozem, Chernozem, Greyzem, Phaeozem	Borolls
Brown Chernozem	Kastanozem (aridic)	Aridic Boroll subgroups
Dark Brown Chernozem	Kastanozem (Haplic)	Typic Boroll subgroups
Black Chernozem	Chernozem	Udic Boroll subgroups
Dark Grey Chernozem	Greyzem	Boralfic Boroll subgroups, Albolls

See also

• Terra preta
• Dark earth

References

1. ^ "blackland". Merriam-Webster Online Dictionary. 2008. http://www.merriam-webster.com/dictionary/blackland. Retrieved 2008-07-07. 
2. ^ "chernozem". Merriam-Webster Online Dictionary. 2008. http://www.merriam-webster.com/dictionary/chernozem. Retrieved 2008-07-07. 

External links

• Pedosphere.com

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