THE MIAMI SERIES OF SOILS. 43 



what remote from lines of pronoimced 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 

 m southern Michigan, west-central Ohio, and eastern Indiana, the 

 drainage of the type is unusually good, and for this reason it was fre- 

 quently 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 cool 

 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 



