4 SOILS OF THE EASTERN UNITED STATES. 



CHARACTERISTICS OF SOIL AND SUBSOIL. 



The surface soil of the Memphis silt loam in its characteristic de- 

 velopment is a brown or brownish-yellow silt loam, containing nearly 

 80 per cent of silt and 15 to 20 per cent of clay, with very small 

 amounts of coarser material, although a little very fine sand is not in- 

 frequently present. The depth of this surface soil varies materially 

 in the different parts of any area where it may be developed. Upon 

 all the steeper and more hilly portions of the type the surface cover- 

 ing is from 2 to 4 or 5 inches thick, while upon the more level areas, 

 where erosion has not been so active, the surface brown loam may 

 attain a depth of 8 to 15 inches. It grades downward into a choco- 

 late-brown to yellow silt loam, which is a little more stiff and com- 

 pact than the surface soil, through the presence of a slightly higher 

 content of clay. 



This material usually extends to a depth of 3 feet or more, and in 

 the majority of cases rests directly upon the soft but compact yellow 

 silt, sometimes mottled with gray, which constitutes the characteristic 

 section of the loess wherever it is fully developed. In other instances, 

 and particularly near the eastern margins where the total thickness 

 of the loess dwindles to 3 or 4 feet, the deep subsoil may be somewhat 

 modified by the presence of small amounts of medium to coarse sand, 

 with occasional pebbles and noncontinuous bands of gravel. In such 

 instances the entire section is liable to be distinguished by a brown 

 or chocolate color. In the less eroded areas where weathering has 

 proceeded uninterruptedly to greater depths, the subsoil is reddish- 

 yellow to a deep chocolate brown. In such instances it is frequently 

 somewhat more stiff and clayey through the breaking down of the silt 

 particles and may locally be known as yellow or red " clay," depend- 

 ing upon the prevalent color tone. 



The Memphis silt loam is usually sharply contrasted with all of 

 the soils in the region where it occurs. In the first place, it is the 

 one great silty soil which extends from southern Illinois southward 

 through the Coastal Plain region to the Gulf of Mexico, being con- 

 trasted with the more sandy or more clayey soils derived from other 

 formations in the general region. It is widely known by a number 

 of popular terms, such as the " brown loam " or the soil of the " Cane 

 Hills " and " Flat Hills " regions where it occurs. 



It has been found desirable in all of the more recent surveys to 

 separate this material on the basis of the topography and prevalence 

 or absence of erosion into two soil types. Of these the more eroded, 

 or the rolling and hilly section commonly found in the " Cane Hills *' 

 district, constitutes the characteristic Memphis silt loam, while the 

 less eroded brown loam of the " Flat Hills " section has in several 

 instances been mapped as the Richland silt loam. The erosion fea- 



