EUSSIAN SOIL INVESTIGATIONS. 809 



The chernozem territory is au undulating- plain with occasionally 

 exten.si\'e elev^ations and furrowed by ravines and river valleys. 

 There is no doubt that in prehistoric times it was flatter and more 

 uniform than at present. The climate is preeminently continental, 

 but with less pronounced characteristics than in the zone of the dry 

 steppes. The annual rainfall fluctuates between -iO and 50 cm., 30 cm. 

 occurring- during- the period of plant growth. Agriculture suffers 

 occasionally from droughts and from high w'inds which are sometimes 

 intensely cold and at other seasons hot and di-y. It is believed that at 

 an early period of the history of the steppes, when their surface was 

 more uniform and retained the cover of dead vegetation, the moisture 

 conditions of the soil during winter were better than they are at pres- 

 ent, although it is not likely that there was ever an excess of water. 

 The chernozem zone of southern Russia has never been an uninter- 

 rupted swamp, as has been maintained by some scientists who believe 

 the chernozem to be derived from the decomposition of peat. It was a 

 prairie with a luxuriant growth of grass. Its natural plant cover 

 consisted mainly of thick tall grasses interspersed here and there with 

 bushes and shrubs. There were originally no forests except on the 

 sandy strips and in the river valleys. The investigations of Ruprecht, 

 Middendorf, Krasnov, Tanfilyev, Korzhinski, and other geobotanists 

 have explained the complex character of the vegetation of these 

 steppes meadows.^ 



Chernozem is as a rule formed by the admixture of humus with loess, 

 but it is also sometimes derived from other parent rocks. In general, 

 it may be stated that calcareous formations which 3deld fine particles 

 on weathering- are more favorable than other rocks to the formation 

 of chernozem. In addition to this, there must be a particular com- 

 bination of topography, vegetation, climatic conditions, etc., favorable 

 to the accumulation of hunms in the soil. Chernozem is usually black, 

 the shade varying in intensity and passing- sometimes into chocolate 

 and cinnamon. Its average depth is about a meter, but this varies, 

 the sandy chernozems being generallv deeper than the clayey. The 

 structure of the uncultivated soil is granular, the aggregates being 

 from 2 to 4 mm. in diameter. As the soil merges into the subsoil this 

 structure disappears and the soil becomes more compact and irregular 

 in color, graduall}" assuming a brown color as it merges into the parent 



^ The list of plants growing on these steppes includes Adonis vernalis, A. wolgensis, 

 Pxonia tenuifolia, Lavatcra thuringiaca, Linnm pereiuw, L. flavum, Medicago fahxtia, 

 Aster amellus, TrlfoliumspY)., Oxgtrojns pilosa, Onobrychis mtlva, Vicia tenuifolia (and 

 others), Centaur ea mar Hchalliana, C. rathenica, Scorzonern jjurpiirea, Hicracium virosum, 

 Campanula sibirica, Echium rubrum, Lychnis chalcedonica, Tliymus marschallianus, Salvia 

 pratensis, S. nutans (and others), Nepeta nuda, Phlomis tnberosa, Ajuga genevensis, 

 Euphorbia procera, Asparagus officinalis, Poa pratensis, Festuca ovina, Siipa pennata, 

 S. capillata, and others. 



17622— No. 2 



