THE MIAMI SERIES OF SOILS. 43 
what remote from lines of pronounced stream drainage, are usually 
wet and poorly drained. This is due both to the level surface of the 
soil and to the great depth of the massive, stiff glacial clay from 
which the soil itself has been formed. Thus, both the surface drain- 
age and the internal soil and subsoil drainage are deficient over such 
areas. In the more rolling portions, such as comprise extensive areas 
in southern Michigan, west-central Ohio, and eastern Indiana, the 
drainage of the type is unusually good, and for this reason it was fre 
qnently selected for settlement in pioneer days. In no case is the 
drainage of the Miami clay loam excessive. 
Erosion constitutes a soil problem only in the steeper sloping 
areas of the Miami clay loam where the land breaks sharply from the 
general upland level down to the valley of some deeply incised 
stream course. Such areas are usually maintained in forests or 
woodlots, or at most are occupied for permanent pasture, so that 
the erosion problem upon this type is scarcely worthy of serious 
consideration. 
The organic-matter content of the surface soil varies with the 
slope of the type and with its condition of natural drainage. In 
lower lying hollows and at the lower altitudes there is a tendency 
toward the accumulation of organic matter, resulting in the darker 
brown to black coloring of the surface soil and frequently in a more 
mealy and friable structure. In such locations the material grades 
toward the soils of the Clyde series, the silty clay member of which is 
generally associated with this type. Over the greater part of the 
area of the Miami clay loam the surface soil is brown or gray in 
color. In such areas a moderate amount of organic matter is present 
within the surface soil and the best conditions for crop production 
are thus indicated. On steep slopes, where erosion has been active, 
the surface soil is frequently absent and the brown, pale-yellow, ash- 
colored or blue subsoil material is exposed. Very little organic 
matter is present in the surface material of such areas, and the in- 
corporation of organic manures is necessary. In general, the or- 
ganic-matter content of the Miami clay loam, particularly in for- 
ested regions, is about the average for upland glacial soils. 
All areas of the Miami clay loam mapped lie within the coo 1 , 
temperate region of central United States, which is supplied with 
abundant but not excessive rainfall. This fact, coupled with the 
fine texture and dense structure of the soil material itself, restricts 
the use of the soil to the production of general farm crops, particu- 
larly the small grains and grasses. Thus the Miami clay loam is a 
general farming soil rather than a special-purpose soil, and its crop 
adaptations are such as to encourage the production of small grains. 
The increased yields of the general farm crops secured upon such 
tracts of this type as have been adequately tile drained indicate that 
