8 
IOWA ACADEMY OF SCIENCE 
SOILS OF WESTERN IOWA. 
The Bureau of Soils of the United States Department of Agri- 
culture has made a study of the soil types in Pottawattamie 
eounty. The general account of these soils is given in the 
Bulletin of Bureau of Soils, The Soils of the United States.^^ 
There are seven different types of soil of general distribution 
along western Iowa. On the low bottoms along the Missouri 
river there are numerous large areas of ‘‘Wabash silt clay’’ 
which is commonly known as “Gumbo.” In the old lake beds 
there is a good deal of a fine “Sandy loam.” Around some of 
the lakes and on sand-bars of the Missouri river there is a pure 
“'sand.” Bordering the “Gumbo” and resembling it to a cer- 
tain extent but generally on slightly higher ground is found the 
“Wabash Silt Loam” which is a very dark and heavy soil but 
is not as sticky as “gumbo.” On the second bottoms is found 
the “LaCrosse silt Loam” which is a chocolate-colored clay. 
This merges into , a lighter colored soil called the Marshall silt 
Loam and a still lighter colored soil which forms the bulk of the 
clay bluffs along the Missouri river is the “Knox silt Loam.” 
Most of the timbered areas are found on the “Marshall silt 
loam” or the “LaCrosse silt loam.” However the “sand” and 
“fine sandy loam” are generally characterized by a growth of 
Salix fUiviatilis, Salix nigra and Populus delt aides. These same 
species are generally found on the gumbo soils with addition of 
Salix missouriensis, Salix amygdaloides and acer saccharinum. 
The bur oak spreads beyond the usual belt of timber, often 
growing in clumps of two or three together. The buck brush 
( Symphoricarpos otcid.entalis), and common sumach usually 
fringe the borders of woods and often occur in patches on the 
slopes of hills and ravines. These shrubs undoubtedly precede 
the growth of trees, making humus. The under growth, especi- 
ally on the edge of the forest, consists of prickly ash {Zanthox- 
ylum americanum) , which frequently forms thickets in the drier 
and more exposed places. The Symphoricarpos occidentalis may 
be common. Here too occurs the common prairie rose {Rosa 
pratincola). In woods, especially near the base of the hills in 
somewhat more open spaces, there is an abundance of the wild 
grape {Vitis vidpina) and the Virginia creeper {Psedera 
vitacea), while an occasional black haw {Viburnum lentago) is 
2iSoils of the United States. Bull. 96, Bureau of Soils, U. S. Dept, of 
Agriculture. Curtis F. Marbut, Hugh H. Bennett, J. B. Dapham and M. H. 
Bapham. 791 f. 13, 1 pi. 1913. 
