808 EXPERIMENT STATION RECORD. 



and over the coast of the Black Sea. In Asiatic Russia these soils 

 cover parts of Uralsk, Turgai, Akmollinsk, and Semipalatinsk. The 

 annual rainfall of this soil zone varies from 30 to -iO cm., one-third of 

 which occurs during the three summer months. The natural vegeta- 

 tion consists mainly of drought-resisting grasses and other plants 

 which dry up early in the season and are driven about over the steppes 

 b}" the winds. The predominating parent rocks of these soils are 

 brownish, greenish gra}", and reddish Post-Tertiary clays, compact, 

 frequently marly, and containing gypsum and soluble salts in some 

 instances. In other cases they are loess-like or sandy. Rock fragments, 

 pebbles, etc., are also found in the soils. The conditions in this soil 

 zone are not favorable to rapid weathering. Light brown or brown- 

 gray soils, poorer in humus, occupy the southern or more strictly 

 desert portion of the belt. The chestnut soils, richer in humus, and 

 merging into the chernozem, are found in the northern portion. The 

 upper horizon of the first class of steppe soils is not more than 1 ft. 

 in depth and gradually merges into the subsoil. The humus content 

 is variable, but averages about 2 per cent. The humus is very slightly 

 soluble in water except when alkaline salts are present. The richness 

 of the humus in nitrogen is a characteristic feature of these soils. In 

 a sample of steppe soil which contained only 1 per cent of humus there 

 was found 0.12 per cent of nitrogen, equivalent to 12 per cent of nitro- 

 gen in humus. A similar observation has been made by Hilgard 

 regarding the nitrogen content of the humus in soils of the arid region 

 of America (E. S. R., 6, p. 197), The amount of zeolites found varied 

 from 8 to 12 per cent. The amount of matter soluble in cold 1 per 

 cent hydrochloric acid, excluding the carbonates, was 1^ to 2 per cent. 

 The upper horizon of the chestnut soils is from 1 to li ft. deep. These 

 soils contain on the average from 3 to 4 per cent of humus, the amount 

 sometimes being as high as 5 per cent. From 2 to 3 per cent of the 

 soil is soluble in cold 1 per cent hydrochloric acid. A bulk analysis 

 of subsoil from this zone showed silica 68.2 per cent, alumina 11.56 

 per cent, iron oxid 3.56 per cent, lime 1.63 per cent, magnesia 1.92 

 per cent, potash 1.98 per cent, soda 1.36 per cent, carbon dioxid 3.74 

 per cent, and phosphoric acid 0.15 per cent. Similar soils are found 

 in California, Colorado, New Mexico, and other parts of the arid 

 region of the United States. 



Chernozem. — The southern third of European Russia is preemi- 

 nentl}^ a region of chernozem. The area occupied by it reaches 

 approximately 216,000,000 to 270,000,000 acres. The chernozem 

 zone extends from the southwestern boundaries of Russia, over the 

 basins of the Dnieper, Don, and part of the Volga, to the southern 

 half of the Ural Mountains. It also extends beyond the Ural River 

 and into Asiatic Russia, although it does not form a continuous belt 

 over the mountainous region of eastern Siberia. All of the chernozem 

 soils of Russia are found between 11 and 57° north latitude. 



