SOIL RELATIONS 239 



all the southeast portion of European Russia, and ex- 

 tends northeast and southwest. North of it lies the 

 non-chernozem, which includes the gray forest lands. 

 The area of the chernozem is said to be about 270,000,000 

 acres. Within it there are occasional small forest tracts, 

 as might be expected, and also other variations in the 

 form of calcareous districts, especially on the west of the 

 Volga River. In the direction of the Caspian Sea, as the 

 climate increases in dryness, are numerous salt marshes 

 and other alkaline wastes, and nearer to the sea great 

 stretches of drifting sand. These are well known char- 

 acteristics of all dry steppes, but are mentioned to indi- 

 cate similarity to our western Great Plains. 



It should be stated that the chernozem in the south- 

 west really begins in the plains of Hungary, where 

 the excellent Hungarian winter wheats are grown. In 

 the east it also extends across the Ural River far into 

 Siberia. 



251. Soil divisions of the chernozem. Dockuchaev, 

 in mapping the soils of the chernozem, divides it into 

 three parts, the southwestern, the central, and the dis- 

 trict east of the Volga, (a) In the southwestern 

 part the soils are dark brown, with humus 4.5 per cent, 

 soil thickness 32-36 inches, maximum 5 feet, and usual 

 subsoil sandy-clay loess. (6) In the central part there are 

 black soils with humus 8.9 per cent, soil thickness 26-28 

 inches, maximum 45 inches, and a usual subsoil of sandy- 

 clay loess, more rarely a mixture of efflorescent chalk 

 with a cretaceous clay, (c) In the part east of the Volga, 

 the soils are black, with humus 9-10 per cent, soil thick- 

 ness 24-26 inches, maximum 38 inches, derived from 

 Permian and Triassic rocks. Adjoining the last-named 

 part there is in western Siberia a continuation of the 



