_ 



THE MEMPHIS SILT LOAM. 5 



tures and the consequent topography, together with their resultant 

 effects upon agriculture, constitute the fundamental basis for this 

 separation. The materials are practically the same, except that in 

 the case of the Richland silt loam the surface brown silty loam 

 material normally extends to a depth of 10 or 15 inches, while in the 

 case of the typical Memphis silt loam it has a depth varying from 2 

 to 12 inches. 



Along the eastern margin of the region in which this silty material 

 is developed, where the total depth of the loess is less than 3 feet, the 

 presence of the red or reddish-yellow sands and gravels of an older 

 formation gives rise to a type of soil known as the Lexington silt 

 loam, distinguished by the presence of this sand and gravel in the 

 deeper subsoil. 



SURFACE FEATURES AND DRAINAGE. 



The usual topography of the typical Memphis silt loam is rolling 

 to hilly. The type occurs along the rivers. At places more remote 

 from the bluff-line the surface becomes slightly rolling to undulating, 

 and in all of the more remote upland occurrences of the type there 

 are considerable areas of practically flat land, which in the later 

 classification will probably be classed as the Richland silt loam, be- 

 cause of this topographic difference. 



The Memphis silt loam follows the bluff-lines bordering the Mis- 

 sissippi drainage in Missouri, southern Illinois, and in western Ken- 

 tucky, Tennessee, and Mississippi. This bluff rises to an altitude 

 of 150 to 250 feet above the adjoining bottom lands or above the 

 waters of the river itself, which frequently wash the foot of the 

 bluff. For a considerable distance back from the bluff-line the front 

 of the escarpment is broken at frequent intervals by deep V-shaped 

 valleys, through which the short tributary streams flow down to 

 the main drainage courses of the bottom land. At greater intervals 

 the larger streams have cut broad valleys through the soft loessial 

 deposit or have formed basins and amphitheaters that open out into 

 the Mississippi bottoms. Away from the crest of the escarpment 

 the surface of the country consists of sharp ridges and cross ridges 

 separated from one another by narrow, steep-sided valleys. The 

 crests of these ridges are frequently level and are occupied by tilled 

 fields. They become broader as one passes away from the bluff-line 

 until they merge into the level plateau of the more remote upland, 

 covered principally by the Richland silt loam. All of the minor 

 streams which flow into the larger tributaries or directly down to the 

 Mississippi itself have cut back rapidly into the soft, unconsolidated 

 materials of the Memphis silt loam, giving rise to a network of 

 minor stream channels and gullies, spreading out like the branches 

 of a tree. With every heavy rainstorm each of these valleys or 



