4 SOILS OF THE EASTERN UNITED STATES. 



streams and the narrower trenches of their local tributaries. The 

 surface of this plain is chiefly occupied by the Marion silt loam, and 

 in some regions it comprises nearly 90 per cent of entire counties. 

 It is the dominant soil of the gray prairies, and is only interrupted 

 by the darker colored silty soils covering the morainal ridges and 

 distributed along the bluffs of larger streams like the Mississippi 

 River. In east- central Missouri the surface of the Marion silt loam 

 is considerably more rolling, and it is even found upon some of the 

 steeper slopes adjacent to the larger streams. 



In general the Marion silt loam is marked by an almost flat surface 

 which only locally is interrupted by slopes or more rolling topog- 

 raphy. 



The absolute elevation of the Marion silt loam above sea level 

 ranges from an altitude of approximately 500 feet in south-central 

 Illinois to elevations of about 750 feet in Missouri. It is usually 

 found at an elevation of 1C to 50 feet above the channels of the 

 streams which flow through the prairie. 



The natural drainage of the Marion silt loam is poor. In fact, 

 the first settlers upon these prairies found them to be wet and swampy, 

 with many ponds and bogs scattered over the surface. The drainage 

 conditions have been improved considerably since that time, but even 

 now, after the heavy rains of winter and spring, water stands for 

 considerable periods over the more level surfaces remote from natural 

 drainage channels. The almost level surface, the dense and slightly 

 pervious subsoil, and the general presence of a " hardpan " layer 

 at the surface of the subsoil, all tend to prevent adequate surface or 

 internal drainage of the type. Improvement in this respect con- 

 stitutes one of the greatest needs of the Marion silt loam. 



In some restricted areas, where the Marion silt loam adjoins the 

 deeper-cut stream channels, some difficulty is experienced with soil 

 erosion. The surface soil is removed by the rains of winter and 

 spring, exposing the white silty " hardpan " layer at the surface and 

 practically destroying the agricultural value of the soil. Such areas 

 are confined to the steeper slopes and constitute only a small per- 

 centage of the total extent of the type. 



LIMITATIONS IN USB. 



The physical characteristics of the Marion silt loam decidedly 

 restrict its uses for agricultural purposes. The compact condition 

 of the subsoil, the presence of the " hardpan " layer, and the general 

 deficiency in natural drainage all tend to limit variety in agricul- 

 ture and nearly all of the deeper-rooting crops are produced only at 

 a disadvantage. This excludes corn from profitable cultivation and 

 restricts the Marion silt loam to the growing of winter wheat, oats, 



