Chernozem
Chernozem (from ; "black ground"), also called black earth or black soil, is a black-colored soil containing a high percentage of humus (4% to 16%) and high percentages of phosphoric acids, phosphorus, and ammonia. Chernozem is very fertile and can produce high agricultural yields with its high moisture storage capacity. Chernozems are a Reference Soil Group of the World Reference Base for Soil Resources (WRB). Distribution. The name comes from the Russian terms for black and soil, earth or land ("chorny" + "zemlya"). The soil, rich in organic matter presenting a black color, was first identified by Russian geologist  Vasily Dokuchaev in 1883 in the tallgrass steppe or prairie of European Russia. Chernozem cover about 230 million hectares of land. There are two "chernozem belts" in the world. One is the Eurasian steppe which extends from eastern Croatia (Slavonia), along the Danube (northern Serbia, northern Bulgaria (Danubian Plain), southern and eastern Romania (Wallachian Plain and Moldavian Plain), and Moldova), to northeast Ukraine across the Central Black Earth Region of Central Russia, southern Russia into Siberia. The other stretches from the Canadian Prairies in Manitoba through the Great Plains of the US as far south as Kansas. Similar soil types  occur in Texas and Hungary. Chernozem layer thickness may vary widely, from several centimetres up to 1.5 metres (60 inches) in Ukraine, as well as the Red River Valley region in the Northern US and Canada (location of the prehistoric Lake Agassiz). The terrain can also be found in small quantities elsewhere (for example, on 1% of Poland). It also exists in Northeast China, near Harbin. The only true chernozem in Australia is located around Nimmitabel, with some of the richest soils in the nation. Previously, there was a black market for the soil in Ukraine, where it is known  as chornozem (). The sale of agricultural land has been illegal in Ukraine since 1992 until the ban was lifted in 2020, but the soil, transported by truck, was able to be sold and bought. According to Kharkiv-based "Green Front" NGO, the black market for illegally acquired chernozem in Ukraine was projected to reach approximately US$900 million per year in 2011. Canadian and United States soil classification. Chernozemic soils are a soil type in the Canadian system of soil classification and the World Reference Base for Soil Resources. History. Theories of Chernozem origin: As seen in the list above , the 19th and 20th-century discussions on the pedogenesis of Chernozem originally stemmed from climatic conditions from the early Holocene to roughly 5500 BC. However, no single paleo-climate reconstruction could accurately explain geochemical variations found in Chernozems throughout central Europe. Evidence of anthropomorphic origins of stable pyrogenic carbon in Chernozem led to improved formation theories. Vegetation burning could explain Chernozem's high magnetic susceptibility, the highest of the major soil types. Soil magnetism increases when soil minerals goethite and ferrihydrite convert to maghemite on exposure to heat. Temperatures sufficient to elevate maghemite on a landscape scale indicates the influence  of fire. Given the rarity of such natural phenomenon in the modern-day, magnetic susceptibility in Chernozem likely relates to control of fire by early humans. Humification can darken soils (melanization) absent a pyrogenic carbon component. Given the symphony of pedogenic processes that contribute to the formation of dark earth, the term Chernozem summarizes different types of black soils with the same appearance but different formation histories.