SOILS OF THE EASTERN UNITED STATES AND THEIR USE XXXIV. 



THE MAKION SILT LOAM. 



GEOGRAPHICAL DISTRIBUTION. 



The Marion silt loam is an extensively developed prairie soil 

 occurring in southern Illinois and in east-central Missouri. Four 

 soil surveys, located in these two States, have included 694,040 acres 

 of this type within their limits. A considerable area of the type is 

 to be found to the south of the region in which it has 'thus far been 

 mapped in southern Illinois, and it is probable that the total area 

 of this soil amounts to several million acres. 



CHARACTER OF SOIL AND SUBSOIL. 



The surface soil of the Marion silt loam to an average depth of 

 12 inches is a gray, ash-colored, or yellowish-white silty loam which 

 normally consists of 70 to 80 per cent of silt with which is mingled 

 an appreciable quantity of fine and very fine sand and about 10 per 

 cent of clay. This is underlain by a layer of white, powdery, siliceous 

 silt, containing numerous small concretions of hydrated iron oxide. 

 In some instances this layer is fully a foot thick; in others it is 

 almost wanting. The deeper subsoil consists of a hard, intractable, 

 silty clay having a mottled gray and brownish-yellow color. When 

 dry this clay becomes checked and jointed, but when wet it is sticky 

 and dense. At varying depths this material rests upon a gravelly 

 bowlder clay which underlies the entire region. The total depth of 

 the soil and subsoil, over the underlying till, varies from 2 or 3 feet 

 to 10 or 15 feet. 



The Marion silt loam is easily distinguished from the other soils 

 of the region in which it occurs by the gray or ash-colored surface 

 soil and the almost universal presence of the " hardpan " layer. 

 The other silty soils of the region are prevalently dark brown or 

 yellowish brown at the surface, and their subsoils are far less com- 

 pact and impervious. 



SURFACE FEATURES AND DRAINAGE. 



Throughout the region in which the Marion silt loam predomi- 

 nates in south-central Illinois the surface of the country consists 

 of a broad, nearly level upland interrupted only by low, rolling 

 morainal ridges and by the broad shallow valleys of the main 



26446 12 3 



