18 
SOIL SURVEY OF BUFFALO COUNTY. 
organic matter than typical. While a number of such minor 
variations occur, this soil, taken as a whole, is remarkably uni¬ 
form. 
Extent and Distribution .—The Knox silt loam, with its steep 
phase, is one of the most important soil types in Buffalo County. 
It occurs in all parts of the county and occupies the limestone 
ridge tops of the entire upland portion of the survey. It lies at 
a higher level than any other type and includes all of the lands 
above the rough stony escarpments. It also covers many of the 
valley slopes descending to the level valley terrace soils. 
Topography and Drainage .—The topography of the Knox silt 
loam as it occurs on the ridge tops may be classed, in most cases, 
as undulating to gently rolling. On the narrower ridges and at 
the heads of valleys it becomes more rolling and grades into the 
steep phase, while over portions of the broader ridges the surface 
is nearly level. That part of the typical soil occupying the lower 
slopes and lower outlying ridges is gently rolling, but often 
grades abruptly into the steep phaze or Rough Stony land. 
On account of the fine texture and the peculiar structure of 
this soil a considerable proportion of the type is subject to ero¬ 
sion, and care must be exercised in selecting crop rotations and in 
the cultivation of all slopes, even though the slope is gentle. 
Some erosion will take place even on rather gentle slopes where 
intertilled crops are grown or where the ground is left bare and 
not cultivated for a considerable time. Wherever the slopes are 
so steep that intertilled crops can only be grown at intervals, 
or where no crops other than grass can be grown without danger 
of serious erosion, such slopes have been included with the steep 
phase. 
Owing to the character of the topography, the natural surface 
drainage of the type is good, so that tile drains will doubtless 
never be necessary except possibly on some of the broader ridges, 
where the surface is more nearly level than elsewhere. 
Origin .—The Knox silt loam has the uniform silty texture, 
the buff-colored subsoil, and other held characteristics of a loes- 
sial formation, though it is considered that part of the material 
has been derived from the underlying rock, the lower Magnesian 
limestone. The material forming this soil is sometimes found to 
be in a slightly acid condition. The subsoil is less acid than the 
soil, and frequently shows no acidity at all. 
