by Andrei SMAGIN, Dr. Sc. (Biol.), Professor of the faculty of Soil Science, Lomonosov Moscow State University, head of the laboratory of control of substance circulation and fluxes of energy in pedosphere of the Institute of Ecological Soil Science, Moscow State University Unique soils, possessing superpowerful humic horizons, are widely spread in the steppes and forest steppes of Eurasia, in the prairies of North America and some other regions of the world. They represent chernozems, universally recognized standard of fertility. Today they make up more than 15 percent of cultivated by man lands, though they lost almost one third of their organic substance as compared with the 19th century level. What are the reasons of such degradation and is it possible to break a dangerous tendency? Black earths occupy an area of 2.3 • 106 km2, which makes up approximately 2.5 percent of biologically productive lands of the Earth. Their large-scale assimilation for production of grain cultures in Eurasian and North American continents began, probably, in late 18th-early 19th cent. due to the development of serf landownership in the Russian Empire and slave plantationship (farming) in the USA. At present these territories are ploughed up or occupied by pastures, only in reserves have been preserved small plots of initial wild steppes (prairies). Chernozems are not accidentally recognized as an apix of bonitation scale of soil quality: their humic-accumulative horizons, with more than 1 m vigor, have a stable granular structure and besides, a neural or weakly-alkaline reaction of the medium (pH), absorption capacity up to 35-55 mole/kg, humus content more than 8-10 percent--properties, providing unprecedentedly high стр. 23 fertility. Unfortunately, today we observe their degradation everywhere: the level of organic substance content, fixed in late 19th cent. by the great Russian scientist, founder of genetic soil science Vasily Dokuchaev, who ha ... Читать далее