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BUREAU OF CHEMISTRY AND SOILS, 1927 
under a heavy forest cover. Small areas of prairie land, which is 
extensively developed in Fond du Lac County, bordering Winnebago 
County on the south, occur in the southwestern part. These small 
prairie areas originally supported a heavy growth of grass, and 
conditions were favorable for the development and preservation of 
a fair supply of organic matter, which is responsible for the dark 
color of the prairie soils. The upland soils within the forested part 
of the county accumulated a much smaller supply of organic matter, 
which came chiefly from decaying leaves, roots, and twigs, and these 
soils are light colored. Under cultivation the dark-colored surface 
layer of the forested upland soils, which in few places extends to a 
greater depth than 2 inches, is soon lost, and cultivated fields show 
a grayish-brown color. 
  All the upland soils have been leached and have become acid to a 
greater or less degree, and much of the lime which was originally 
present has disappeared, so that the surface soil, or A horizon, of 
most of these soils shows a slight or medium acid reaction, but the 
soils have some lime in the lower part of the subsoil, or B horizon 
and almost everywhere a fair supply in the parent material, or d 
horizon. 
  The soils of this county may be broadly classed in two groups, the 
well-drained soils and the poorly drained soils. The well-drained 
soils may be divided into a dark-colored, or prairie, subgroup and a 
light-colored, or forested, subgroup. The dark-colored prairie soils 
are correlated in the Parr series, and the light-colored forested soils 
in the Superior, Kewaunee Bellefontaine, Miami, Plainfield, and 
Coloma series. The forested soils may also be divided on the broad 
basis of texture, soils of the Plainfield and Coloma series being 
mostly sandy soils, and soils of the other upland series being mainly 
heavier soils. The group of poorly drained soils may be divided into 
two subgroups, poorly drained, dark-colored mineral soils of mod- 
erate organic-matter content, such as the Clyde, Poygan, and Mau- 
mee soils, and soils composed dominantly of organic matter. 
  The well-drained normally developed soils of the region have 
reached the stage of maturity in which the three horizons are evident. 
These include the soils of the Superior, Kewaunee, Miami, Belle- 
fontaine, and Parr series. In virgin areas the forested soils have a 
thin dark-colored surface layer, an inch or two thick, consisting of 
leaf mold, grass roots, and other organic matter, but the dark color 
and much of the organic matter are lost when the soil is cultivated. 
The surface soil, or A horizon, is light colored, usually loam, silt 
loam, or silty clay loam in texture, as heavy soils predominate, has 
been leached of its lime and is slightly acid to a depth ranging from 
8 to 12 inches, and the finest particles have been carried downward 
and depositeil in the B horizon. 
  The B horizon, commonly called the subsoil, is the zone of accumu- 
lation and is everywhere heavier than the surface soil. In this county 
it is usually clay or clay loam in texture. This heavy zone of 
accumulation, or the zone of illuviation, extends to a depth ranging 
from 28 to 36 inches, where it rests on the C horizon, or parent 
material. 
  The C horizon is usually looser, somewhat lighter in texture, and, 
in the heavier soils, is rich in lime.