COUNTY SOIL SURVEY REPORTS
LABORATORY EXERCISE #7
OBJECTIVES
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Use a soil survey report to evaluate soil resources.
Understand soil survey reports and how to utilize the information that is provided.
Be able to answer all the Study Questions at the end of this laboratory exercise.
INTRODUCTION
Soil Surveys contain information that can be used in land-planning programs for a given
county. The survey contains predictions of soil behavior for selected land uses. The survey
also highlights limitations and hazards inherent in the soil, improvements needed to overcome
the limitations, and the impact of selected land uses on the environment.
The soil survey is designed for many different users. Farmers, foresters, and agronomists can
use it to evaluate the potential of the soil and management needed for maximum food and fiber
production. Planners, community officials, engineers, developers, builders, and home buyers can
use the survey to plan land use, select sites for construction, and identify special practices needed
to insure proper use of the soil. Conservationists, teachers, students, and specialists in
recreation, wildlife management, waste disposal, and pollution control can use the survey to help
them understand, protect, and enhance the environment. Taxes may even be determined from
Soil Surveys. In many states, taxes on farm land are based on soil type and Soil Surveys are used
to figure the land's tax value.
The Natural Resources Conservation Service (NRCS) of the USDA prepares Soil Surveys by first
identifying the soils in the county. This is done by dividing the landscape into areas containing
similar pedons and polypedons. Usually the landscape areas are divided on the basis of slope,
erosion, and soil series and recorded on an aerial photograph.
http://websoilsurvey.nrcs.usda.gov/app/
The actual process of mapping or surveying consists of walking over the landscape at regular
intervals and taking notes of soil differences and all related surface features, such as slope
gradient, evidence of erosion, land use, vegetative cover, and cultural features. Boundaries are
drawn directly on aerial photos representing, in most places, changes from one soil type to
another. These areas within the soil boundaries are termed map units. The symbol within the
mapping unit is identified on the Soil Legend. Each mapping unit consists of a specific soil
series, with the textural class of the A horizon and the slope of the soil also identified. Mapping
units change whenever there is a change in one or more of the 5 soil forming factors. The soils
that are identified and mapped are listed in the Soil Legend which is located just before the
separate map sheets. The locations of these soils are given on the individual map sheets, which
are found in the last half of the report.
It would be nice if individual mapping units contained only the soil identified by the mapping
unit symbol but it is normally not the case. Many times these other types of soils can be found
within the mapping unit boundary. These other soils are not shown because they do not take up
enough area to show up on the map. Generally a mapping unit must be at least 1 to 2 acres in size
in order to be mapped. However, the different soils that can be expected within each mapping
unit are included in the mapping unit descriptions given in the Soil Survey.
To use a Soil Survey, a specific area must first be identified on the map sheets. First refer to
the "Index to Map Sheets" which is found on the same sheet as the Soil Legend. The index
consists of a county map which is overlain by a grid. Each square of the grid represents one
aerial photo (map sheet). The number of the grid is also the number of
that specific map sheet. To determine what soils occupy a specific site in the county, first find
that area on the Index to Map Sheet. Then turn to the specific map sheet.
Once you have found the proper map sheet, you may determine what soils are on the piece of
land in question. The potential land uses and limitations for each mapping unit may be found in
he different tables located throughout the Soil Survey.
Most counties have published soil surveys that can be obtained from your local NRCS. If hardcopy soil survey reports cannot be easily obtained, one could use the Web Soil Survey (WSS) to
locate their region of interest. The Web Soil Survey provides soil data and information for more
than 95% of the nation’s counties and hopes to have all of the soil survey’s on-line in the future.
The site is operated by the USDA Natural Resources Conservation Service (NRCS) and can be
found at http://websoilsurvey.nrcs.usda.gov/app/. In this lab, we will utilize the Web Soil Survey
to become more familiar with soil survey information available to us.
LABORATORY ACIVITY – ONLINE VERSION
1. To become familiar with the contents of a county soil survey we will utilize the
Web Soil Survey (WSS). First, click on the link to the homepage for WSS http://websoilsurvey.nrcs.usda.gov/app/. You should have the following
screen:
2. Second, we will begin web soil survey. Click on the green button that says
“Start WSS” at the top of the homepage:
3. It will take a few seconds for the web soil survey to load, depending on your
internet connection. Once it has loaded you will see that the first screen is
described as the “Area of Interest (AOI)”. This is the default page that allows
you to navigate to your area of interest by several methods such as: address,
state & county, soil survey area, latitude & longitude, PLSS, etc.
4. Let’s try navigating to our area of interest by selecting “State and County”. Left-click on
“State and County” and the following screen should pop up. Choose “North Carolina” as the
state and “Wake” as the county by using the scroll button on the right. Then click “View”.
5. It will take a few second to load, so be patient. A new screen will pop up showing you Wake
County with the surrounding towns labeled in green and the interstates (I-40, I-95, I-440)
labeled in blue.
6. Even though we have a new map, we still haven’t selected an area of interest. We know this
because the other three folders on our screen are grayed out. We have three other folders:
Soil Map, Soil Data Explorer, and Shopping Cart. These are the folders where the soils
information is kept. Once we have selected an area of interest, we will be able to click on
these folders and access the soil information.
7. Let us zoom into an area of North Raleigh using Zoom In tool on the Toolbar.
Zoom In
Zoom Out
Pan
Previous View
Define Area of Interest by Rectangle
Help
Define Area of Interest by Polygon
Zoom to Full Extent
Identify
8. Choose the “Zoom In” Tool on the left-hand side. Now click on the map in the northern area
of Raleigh, near the major road labeled as “50”.
9. Now choose the “Select AOI by Rectangle” Tool (see step #7 for help). After you choose the
proper tool, move your mouse’s cursor near the major road labeled as “50” again. Left-click
your mouse and drag your mouse so that you make a small rectangle. Once you let go of the
left side of the mouse, you will have chosen an area of interest. It will take a few seconds for
the screen to refresh. You should have something similar to the following screen capture.
Your three folders labeled Soil Map, Soil Data Explorer, and Shopping Cart should be black
instead of gray now. If they aren’t then repeat Step #9.
10. Notice that you can now see which soil survey version you are looking viewing. We are
looking at Wake County, North Carolina (NC183) Version 7 revised March 20, 2007.
11. Left-click on the Soil Map Folder tab at the top of the screen. It will take a few seconds for
the soils map to appear. On the right-hand side, we can see our soils map. On the left-hand
side, we can see our map unit legend, which includes information about map unit symbol,
map unit name, acres in our AOI, and the percent of our AOI. At the bottom left-hand corner
are the totals for our AOI.
12. Left-click on one of the blue Map Unit Names to learn more about that map unit. You
should get something similar to the following screen capture. It will give information about
the map unit setting (temperature and rainfall), composition, setting (landform position and
shape), properties (drainage class, frequency of flooding, available water capacity), land
capability classes, and what a typical profile looks like. Spend a few minutes to review the
information given.
13. Once you have finished reviewing the information, close out the window by left clicking on
the “X” in the upper right-hand corner of the Map Unit Description box.
14. To change the display features on the physical map, click the Legend tab on the left-hand
side of the soils map. Scroll through the Legend to see which layers you would like to stay
or add. You can select or deselect by left clicking on the check marks/boxes next to the
legend item. When you have finished with the legend, left-click the Legends tab again with
your mouse to close the legend.
15. To see where the soil map units appear on the soil map, select the “Zoom In” tool and leftclick on the soils map. The Soil Map Unit Symbols will appear on the map.
16. Now that we have explored the Soil Map tab, we can answer Questions #1-5 in the
Laboratory Questions section at the end of this lab.
17. Now, let’s take a look at the Soil Data Explorer tab. Left-click on the Soil Data Explorer tab
and your screen should look like the following.
18. With the Soil Data Explorer, we have four subfolders that include: Intro to Soils, Suitabilities
and Limitations for Use, Soil Properties and Qualities, and Soil Reports. The default once
we open Soil Data Explorer is the Suitabilities and Limitations for Use subfolder. On the
left-hand side, you see that we have a listing of Suitabilities and Limitations Ratings that
include building site development, construction materials, disaster recovery planning, land
classifications, land management, recreational development, vegetative productivity, etc.
19. Open Building Site Development by left-clicking the grey button with two arrows to the right
Building Site Development. The folder opens and you see many subheadings. Let’s explore
Dwellings With Basements. Left-click on Dwellings With Basements. Then select View
Rating (see the screen capture below for help).
20. Now you see that your Soil Map is color-coded according to the limitations of the soils for
dwellings with basements. Red means severe limitations, yellow is moderate, and green
lacks any limitations. You also notice that your soil map units have a rating listed with the
map unit name. Scroll through to see which soil map units have severe limitations.
21. Let’s look at Local Roads and Streets. This subcategory is also under the Building Site
Development category. Left-click on Local Roads and Streets, press View Rating. Scroll
through the map units to see which soils are considered severely limited.
22. Let’s look at septic tank suitability. Under the category of Sanitary Facilites, open Septic
Tank Absorption Fields. Choose View Rating and scroll through your map units. You
should now be able to answer Question #6.
23. Let’s look at how our soils will do with recreational development. Under the category of
Recreational Development, explore the soil suitability of your soils for picnic areas, camp
areas, and playgrounds. Answer Question #7.
24. To determine which soil unit has the best tree productivity, let us look under the category of
Vegetative Productivity. In this category, we can determine the soil’s productivity with
respect to crops, irrigated crops, non-irrigated crops, trees, etc. Choose the Forest
Productivity (Cubic Feet per Acre per Year) option. Now we can answer Question #8.
LABORATORY ACTIVITY
NAME: ___________________________________________
LABORATORY SECTION:
1. Explain briefly how this soil survey was made (look at the introduction material for
assistance).
2.
What type of soils are found in the major associations in your Area of Interest?
3.
Describe the climatic conditions found in your County.
4. Soil capability classifications are ratings of soils based on the soils agricultural capability.
There are 8 classes with Class I having the fewest limitations and Class VIII having very severe
limitations. There are suborders, depending on the limitation (e=erosion, w=wetness, s=shallow
soils, c=climate). A soil with a soil capability classification of 2e, would have only slight
limitations due to erosion problems. Looking at some of your soil map units, what are some of
your soil capability classifications?
5.
What soil is of the largest extent in your Area of Interest? Give its classification.
6. Describe the rating system and the criteria for dwellings with basements, local roads and
streets, and septic tanks fields (what are some of the limitations)?
7.
What soils are good for camp areas, picnic areas, playgrounds, or paths and trails?
Explain the reason for your answers.
8.
Which soil series is rated best for production of loblolly pine?