RUSSIAN SOIL INVESTIGATIONS. 817 



marked contrast witn the .surrounding light gray podzol soils. They 

 are known under the local terms of ''rendzina'' or "borowina,"" The 

 upper horizon of the rendzina is most frequently gra}', without a 

 cinnamon tint, not rarely spotted with white undecomposed chalk; 

 lowei" down the color becomes lighter and the soil graduidl}' merges 

 into the marly, sticky clay which is mixed with chalky gravel. Still 

 lower lies the white parent rock — chalk or limestone. The content of 

 hunnis varies from 3 to 5 per cent and more; its solubility from one 

 one-hundredth to one one-hundred-and-thirtieth. The amount of cal- 

 cium carbonate varies from 8 to IT per cent and more. The clayey 

 character of the mineral matter renders the soil sticky in Avet weather 

 and hard in a drought. However, lighter sandy rendzinas also occur. 



Marsh or stvamp soils. — Soils of this type extend largelv throughout 

 the whole northern half of Russia, but are of little economic impor- 

 tance. In the basin of the Pripet Ri\er they occupy more than 2,000 

 square kilometers. Throughout the podzol soil areas spots and strips 

 of grassy marsh soils are formed under the influence of excessive 

 .stagnating water. The vegetation consists of species of Carex, 

 Scirpus. Phragmites, Acorus, Menyanthes, Parnassia, Nasturtium, 

 Ranunculus, Butomus, Sagittaria, etc. The roots of these plants 

 penetrating into the slimy mineral rock over.saturated with water, 

 give humus which slowly oxidizes and Avhich accumulates in large 

 amounts (4 to 20 per cent). The borders of the marshes are frequently 

 cultivated and are known as " black earth"" in contrast to the adjacent 

 light sod and podzol soils. 



The thickness of the dark-colored horizon varies from 2 to 8 and 

 more decimeters. The solubility of the humus of the soil as a whole 

 is not great (g^ro to -^^j^)^ but rapidly increases with the depth in the 

 .soil, being one-tenth at a depth of 1 meter. The abundance of mois- 

 ture which dissolves humus acids favors the decoloration and leaching 

 of the lower horizons of the soil, making them very similar to the 

 podzols. Under the marshes are frequently found white, light gray, 

 or bluish, and grayish-white .slime, either clayey or sandy. The total 

 quantity of nitrogen in the upper horizon varies from 0.3 to 4 per 

 cent. 



In the mineral part of the soil the proportion of the clay and sand 

 is variable. Brown veins and concretions of limonite, vivianite, iron 

 sulphid, etc., are usually present. A considerable amount of carbon- 

 ate and sulphate of calcium are also characteristic of many marshy 

 .soils which contain animal remains (shells of mollusks. etc.). 



1N('<):\I1'I.ETE OK AZONAL SOILS. 



To this cla.ss belong the crude and skeleton soils originating from 

 compact, pebbly, conglomerate, and sandy rocks, and morainic and 

 alluvial soils, which are more or less widely distributed throughout 



