SOILS OF THE EASTERN UNITED STATES AND THEIR USE-XVIII. 



THE WABASH SILT LOAM. 



GEOGRAPHICAL DISTRIBUTION. 



The Wabash silt loam is a widely distributed type of alluvial soil 

 occurring in the bottom lands of all of the larger south-flowing 

 rivers throughout the Central Prairie States and extending south- 

 ward along their courses to their confluence with the main drainage 

 lines. The type is therefore encountered in a large number of dif- 

 ferent areas with no considerable acreage in any particular case. It 

 has been mapped in 28 different areas found in 9 States and aggre- 

 gating 801,756 acres. It is probable that additional surveys in the 

 same general region will show the existence of considerably larger 

 areas, since practically all of the broader bottom lands along the 

 streams throughout the Prairie States contain large or small develop- 

 ments of this important soil type. 



CHARACTERISTICS OF SOIL AND SUBSOIL. 



The depth of the surface soil of the Wabash silt loam varies to a 

 considerable degree in the different areas where it has been encoun- 

 tered. It is rarely less than 8 or 10 inches and may extend to a total 

 depth of 3 feet, or even more. Within these limits there is every 

 variation, even in small areas. The surface soil is a mellow, brown 

 silty loam which becomes almost black in depressed portions of the 

 type, where there has been a tendency toward accumulation of the 

 mucky surface soil. On the other hand it becomes a lighter brown 

 or a yellowish brown upon the low ridges or undulations which pos- 

 sess the best drainage and are not subject to annual overflow. This 

 material grades downward without any perceptible boundary into the 

 subsoil, which becomes lighter in color with increased depth and at 

 36 inches or more is usually a light-brown, drab, or mottled yellow and 

 gray heavy silty loam. Owing to the alluvial origin of the type, there 

 are minor variations in texture and it frequently occurs that a drab 

 or gray clay may be encountered at the greatest depths, while veins 

 and pockets of sand are encountered here and there in the surface soil 

 or subsoil. There is also a tendency toward the accumulation of some 

 fine sand on the low ridges already mentioned. 



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