Chernozems; General Conclusions - Major Soil Groups of the World - page 450

boundaries more or less parallel to the latitudes. They have escaped the
depletion phenomena that begin further north in the Phaeozems (kind
of precursors of continental Luvisols). They also have kept clear of the
phenomena of calcification and salinization that take place further south
in Kastanozems and Solonchaks. In short, Chernozems correspond to
very fertile regions. They are a little cold but are perfectly well suited
to certain crops: wheat, potato, etc. This applies in particular to Ukraine,
the wheat granary of Russia and in the heartland of North America, the
Corn Belt (Dakota, Minnesota, Montana, Nebraska, Iowa, etc.).
The complete climatosequence of continental soils comprises, from
north to south: Cryosols, Podzols, Albeluvisols, Luvisols, Phaeozems,
Chernozems, Kastanozems, Solonchaks, Solonetz and, lastly, sandy
deserts. Figure 14.2 presents the terms of this progression that concerns
us here. The Chernozem, which corresponds to a P - PET not very far
from zero, is therefore the least differentiated vertically.
Fig. 14.2 Typical sequence in the continental areas. From left to right: Phaeozem or
Luvic Chernozem of Poland with the beginnings of clay depletion from the surface and
start of a light-coloured horizon ( photo : G. Trouche); typical Chernozem of Germany, rich
in organic matter ( photo : Elke Schulz); Kastanozem with accumulation of CaCO 3 in the B
horizon ( photo : A. Ruellan); and, lastly, Solonchak with accumulation of salts on the surface
( photo : A. Ruellan).
Figure 14.3 illustrates the distribution of these soils in North America,
East Europe and Asia. It has been drawn from the FAO Soil Map of the
World.
In Eastern Europe and Asia, zonality is almost perfect. On the other
hand, it is much less discernible in North America because of all kinds of
disruptions: less massive continent, therefore less shielded from marine
influence, more heterogeneous geological substratum, mountain ranges
oriented north to south, etc. It was better to be Russian than American