THE WABASH CLAY. 5 



SURFACE FEATURES AND DRAINAGE. 



The Wabash clay occupies level or depressed areas within the 

 broader alluvial bottom lands. The arable areas of the type, in 

 general, are found in almost absolutely level tracts lying somewhat 

 back from the front lands along the main stream channels, and usu- 

 ally somewhat above the level of the lowest depressions found in 

 the bayous and hollows of the bottoms. In addition to this agricul- 

 turally available land included within the type, there are numerous 

 long, narrow areas of the Wabash clay to be found within the beds 

 of old bayous and in other depressions throughout the bottoms. 

 These latter areas are usually flooded each season. They retain an 

 excess of moisture until far into the summer and are consequently 

 not well suited to agricultural purposes in their natural condition. 

 It is within these latter areas that the characteristic " gumbo " soil 

 is also most frequently encountered. Such areas constitute the region 

 of deposition of the finest sediments carried by the overflow waters. 



The range of the elevation of the surface of the Wabash clay varies 

 from 5 or 6 feet above sea level in the extreme southern portion of the 

 Mississippi Delta to altitudes of 800 or 1,000 feet or even more in 

 the upper drainage tributaries of the Mississippi. The Wabash clay 

 is usually from 5 to 15 feet above the normal level of the streams 

 along which it lies, and the type is consequently subject to frequent 

 overflow, unless artificially protected. Lying so near water level, it 

 is also frequently poorly drained, and this characteristic is more 

 marked because of the stiff, tenacious, impervious nature of the heavy 

 clay subsoil. Thus the Wabash clay is difficult to bring under agri- 

 cultural occupation, and the expense involved in reclamation is 

 frequently heavy. 



The Wabash clay is rarely subject to any form of erosion except 

 through the change in direction of the channels of the main streams, 

 which frequently erode their banks upon the convex curve to rede- 

 posit the materials at lower points in the flood plain. Erosion, how- 

 ever, is not a serious difficulty in connection with the tillage of the 

 Wabash clay, except in a few localities where open ditches and water 

 furrows are improperly constructed. 



LIMITATIONS IN USE. 



The stiff plastic character of the materials constituting the Wabash 

 clay presents serious difficulties in its tillage. Only in such areas as 

 granulate naturally while water is being evaporated from the surface 

 soil is it easy to secure the proper breaking and preparation of the 

 land. Even in such cases, and to a more marked degree in the dense 

 " gumbo " or " beeswax " soils, extreme care must be taken in plow- 

 ing the land to perform that operation when the ground is neither 



