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What is Soil Survey?

This definition is from the Soil Science Society of America:

soil survey - (i) The systematic examination, description, classification, and mapping of soils in an area. Soil surveys are classified according to the kind and intensity of field examination. (ii) The program of the National Cooperative Soil Survey that includes developing and implementing standards for describing, classifying, mapping, writing, and publishing information about soils of a specific area.

Expanded Definition and Uses

photo of soil scientist comparing soil to a color bookSoil survey, or soil mapping, is the process of classifying soil types and other soil properties in a given area and geo-encoding such information. It applies the principles of soil science, and draws heavily from geomorphology, theories of soil formation, physical geography, and analysis of vegetation and land use patterns. Primary data for the soil survey are acquired by field sampling and by remote sensing. Remote sensing principally uses aerial photography but LiDAR and other digital techniques steadily gaining in popularity. In the past, a soil scientist would take hard-copies of aerial photography, topo-sheets, and mapping keys into the field with them. Today, a growing number of soil scientists bring a rugidized tablet computer and GPS into the field with them. The tablet may be loaded with digital aerial photos, LiDAR, topography, soil geo-data-bases, mapping keys, and more.

The information in a soil survey can be used by the public as well as the scientific community. For example, farmers and ranchers can use it to help determine whether a particular soil type is suited for crops or livestock and what type of soil management might be required. An architect or engineer might use the engineering properties of a soil to determine whether or not it was suitable for a certain type of construction. A homeowner may even use the information for maintaining or constructing their garden, yard, or home.

Soil Survey Components

Typical information in a county soil survey includes:

  • A brief overview of the county’s geography.
  • A general soil map with a brief description of each of the major soil types found in the county along with their characteristics.
  • Detailed aerial photographs with specific soil types outlined and indexed.
  • Photographs of some of the typical soils found in the area.
  • Tables containing general information about the various soils such as total area, comparisons of production of typical crops and common range plants. They also include extensive interpretations for land use planning such as limitations for dwellings with and without basements, shallow excavations, small commercial buildings, septic tank adsorptions, suitability for development, construction, and water management.
  • Tables containing specific physical, chemical, and engineering properties such as soil depth, soil texture, particle size and distribution, plasticity, permeability, available water capacity, shrink-swell potential, corrosion properties, and erodibility.

The term soil survey may also be used to describe the published results. In the United States, these surveys were once published in book form for individual counties by the National Cooperative Soil Survey. Today, soil surveys are no longer published in book form; they are published to the web and can be freely accessed by the public on NRCS’ Web Soil Survey (WSS) site, where a person can create a custom soil survey. By making the data and information available online, it allows for the rapid flow of the latest soil information to the user. In the past it could take years to publish a paper soil survey sometime making the published information almost obsolete. Many of the published manuscripts have been scanned for historical purposes.

Understanding the Value

Soil scientists collecting a sample to be sent to the laboratory for analysis.Soil lies beneath each activity.

Soil surveys commonly identify the more important soil characteristics that determine the limitations and qualities of the soil. These interpretations are designed to warn of possible soil related hazards in an area. Knowledge of soil landscapes, soil formation, and the various soil properties and function has expanded with a classification system oriented to the interpretations of the soil survey. Various divisions and subdivisions of the basic system of classification called soil taxonomy provide a basis for application of the information to engineering and agricultural uses of the soil. Information about soil properties provides a basis for assessing risks and hazards when making land use decisions. Additionally, during the soil inventory process, we learn the relationship of various landscapes features to soil geography. Identifying and mapping soil landscape relationships strengthen soil interpretations and the associated interpretations involving hydrology and landscape stability. The separation of geology and soils is not a clear division, but rather the interpretations enhance the delivery of information through the connection of soils to the landscape and the corresponding geology.

Helpful Tools

As part of NRCS’ website, current soil survey data and information in digital form is available to assist with analysis, evaluations, and decision making tasks for both the professional and private citizen. Please visit the Tools page for links to many types of tools and applications.