Soil Surveys Explained
What is a Soil Survey?
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How can I stand on the ground every day and not feel its power? How can I live my life stepping on this stuff and not wonder at it? ---
William Bryant Logan, Dirt-The Ecstatic Skin of the Earth
Soil surveys provide a scientific inventory of one of our most basic and important natural resources-- the soil. The National Cooperative Soil Survey Program is actually a nationwide partnership of Federal, regional, State, and local agencies. The Natural Resources Conservation Service (NRCS), in cooperation with its partners, has the leadership role for conducting soil surveys on private lands across the country. The Vermont NRCS Soils Program works with:
Vermont Agricultural Experiment Station
Vermont Center for Geographic Information
Vermont Agency of Natural Resources
United States Forest Service
Soil surveys provide a variety of users with information about soils and how to manage them properly. Modern soil surveys can be used for such diverse activities as farm planning, forest management, analysis of urban sprawl, watershed modeling, sewage disposal, highway construction, and ecological research. Soil surveys contain interpretative information for agricultural, forestry and urban uses. The survey also highlights limitations and hazards inherent in the soil. A soil survey is a fundamental tool for sound soil and water management, crop production, and land use.
Vermont users of the soil survey find it an invaluable reference to answer questions about:
Important Agricultural Soils (Prime & Statewide rated soils + Primary Agricultural Soils)
On-site Sewage Ratings
Areas prone to flooding
Many people assume that soils are all more or less alike. They are unaware that great differences in soil properties can occur within even short distances. Soils may be seasonally wet or subject to flooding (see Figure 1). They may be shallow to bedrock. They may be too unstable to be used as a foundation for buildings or roads. Very clayey or wet soils are poorly suited to septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations.
A soil survey makes these types of interpretive data easily available to prevent inappropriate uses of soils. By matching land use to soil properties ecological stability is maintained. It is essential to understand soils, know where they occur on the landscape and evaluate their unique properties and limitations.
A multitude of processes are utilized to create soil maps. Initially, the two primary techniques are
field observations from traversing the land
aerial photograph interpretation.
When in the field, soil scientists observe slopes, vegetation, and every feature they believe might affect use of the soil. Additionally, using soil augers and spades they expose soil profiles to determine the characteristics of the soil which results in the soil being classified to the series level. Boundaries of the individual soil areas are drafted on distorted aerial photographs, which permits the mapper to see a three-dimensional view of the landscape by using a stereo-scope. Other available maps of the survey area are consulted such as surficial and bedrock geology maps, flood hazard maps, and vegetation zone maps. While a soil survey is in progress, samples of soils are taken as needed for laboratory measurements and engineering tests.
The St. Johnsbury MLRA soil survey office has pioneered using the Soil Inference Engine developed by a Dartmouth professor, Xun Shi, to integrate GIS technologies into the soil survey mapping process.