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Soil
Survey of Otter Tail County, Minnesota |
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How
This Survey Was Made
This survey was made to provide information
about the soils and miscellaneous areas
in the survey area.
The information includes a description of the soils and miscellaneous areas and
their location and a discussion of their suitability, limitations, and management
for specified uses. Soil scientists observed the steepness, length, and shape
of the slopes; the general pattern of drainage; the kinds of crops and native
plants; and the kinds of bedrock. They dug many holes to study the soil profile,
which is the sequence of natural layers, or horizons, in a soil. The profile
extends from the surface down into the unconsolidated material in which the soil
formed. The unconsolidated material is devoid of roots and other living organisms
and has not been changed by other biological activity. The soils and miscellaneous
areas in the survey area are in an orderly pattern that is related to the geology,
landforms, relief, climate, and natural vegetation of the area. Each kind of
soil and miscellaneous area is associated with a particular kind or segment of
the landscape. By observing the soils and miscellaneous areas in the survey area
and relating their position to specific segments of the landscape, soil scientists
develop a concept, or model, of how the soils were formed. Thus, during mapping,
this model enables the soil scientists to predict with a considerable degree
of accuracy the kind of soil or miscellaneous area at a specific location on
the landscape. Individual soils on the landscape commonly merge into one another
as their characteristics gradually change. To construct an accurate map, however,
soil scientists must determine the boundaries between the soils. They can observe
only a limited number of soil profiles. Nevertheless, these observations, supplemented
by an understanding of the soil vegetation- landscape relationships, are sufficient
to verify predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied.
They noted soil color, texture, size and shape of soil aggregates, kind and amount
of rock fragments, distribution of plant roots, reaction, and other features
that enable them to identify soils. After describing the soils in the survey
area and determining their properties, the soil scientists assigned the soils
to taxonomic classes (units). axonomic classes are concepts. Each taxonomic class
has a set of soil characteristics with precisely defined limits. The classes
are used as a basis for comparison to classify soils systematically. Soil taxonomy,
the system of taxonomic classification used in the United States, is based mainly
on the kind and character of soil properties and the arrangement of horizons
within the profile. After the soil scientists classified and named the soils
in the survey area, they compared the individual soils with similar soils in
the same taxonomic class in other areas so that they could confirm data and assemble
additional data based on experience and research. While a soil survey is in progress,
samples of some of the soils in the area generally are collected for laboratory
analyses and for engineering tests. Soil scientists interpret the data from these
analyses and tests as well as the field-observed characteristics and the soil
properties to determine the expected behavior of the soils under different uses.
Interpretations for all of the soils are field tested through observation of
the soils in different uses and under different levels of management. Some interpretations
are modified to fit local conditions, and some new interpretations are developed
to meet local needs. Data are assembled from other sources, such as research
information, production records, and field experience of specialists. For example,
data on crop yields under defined levels of management are assembled from farm
records and from field or plot experiments on the same kinds of soil. Predictions
about soil behavior are based not only on soil properties but also on such variables
as climate and biological activity.
Soil conditions are predictable over long periods of time, but they are not predictable
from year to year. For example, soil scientists can predict with a fairly high
degree of accuracy that a given soil will have a high water table within certain
depths in most years, but they cannot predict that a high water table will always
be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of
soil in the survey area, they drew the boundaries of these bodies on aerial photographs
and identified each as a specific map unit. Aerial photographs show trees, buildings,
fields, roads, and rivers, all of which help in locating boundaries accurately.
The descriptions, names, and delineations of the soils in this survey area do
not fully agree with those of the soils in adjacent survey areas. Differences
are the result of a better knowledge of soils, modifications in series concepts,
or variations in the intensity of mapping or in the extent of the soils in the
survey areas.
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©Copyright 2001- County of Otter Tail, Minnesota. U.S.A.
All Rights Reserved.
This web site is maintained by the Otter
Tail County GIS Office.
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