Classifying Soil Types

Soil characteristics can help to predict crop performance, therefore it is useful to classify soils. The basis of soil classification is that environments that share comparable soil forming factors produce similar types of soil. The soil type at a given site is the long term consequence of all of the environmental factors, including geological ones, which have prevailed at that site. Knowing the soil type, therefore, gives us information about the above ground environment at the site as well as the substrate for plant growth.

Soils are classified by a taxonomic system, like plant taxonomy, based on relationships between soil types. Soil taxonomy has six hierarchical levels of classification as follows: orders, suborders, great groups, subgroups, families, and series.

Note the Workbook section on soils, p [13-15] . The remainder of Section 4.1 will help you complete p [13].

The MNG Case Study Site Assessment Workbook [] provides example soil survey information.

Soil Surveys

Beginning early in the 20th Century, the US Soil Conservation Service (now the Natural Resource Conservation Service, NRCS) began an extensive process of classifying and characterizing agricultural and other soils throughout the US. According to the NRCS, a soil survey is a “detailed report on the soils of an area”. NRCS soil surveys are available in print from local NRCS offices, local conservation offices and other sources described in the Soil Survey Resource box, below. A NRCS soil survey consists of:

• Aerial photographs (maps) showing the boundaries among different soil types
• Descriptions of each soil type
• Tables of soil properties and features related to the performance of agricultural and forest management for each soil type

Soil survey map (aerial photo) from Soil Survey of Tompkins County, NY. Red lines on the aerial photograph circumscribe different soil type denoted by abbreviations which correspond to the names soil types described in corresponding text and tables.

Locating and Using NRCS Published Soil Surveys

Surveys for your site may be available on the NRCS website [] . If it is not, use the list of surveys by state to find out where you can obtain a print or CD version of the survey for your location [] .

To use a published NRCS (SCS) soil survey (print or online):

• Locate your site using the locator map on the NRCS website (“Area of Interest” tab), CD or printed version of the survey and find the detailed aerial photo/map that applies to your site.
• Use your knowledge of roadways and streams to pinpoint the exact location of your site on the map. Note soil survey abbreviations (e.g. VoB, Ar, CaB, etc.). Use the chart at the beginning of the map section to find the full name of the soil types that apply to your site.
• Write down the names and locations of these soils on your HWWFF Site Assessment Map (a copy of your Base map), outlining the approximate location of each soil type. You’ll want to know locations of different soil types on your site for sections 4.2 & 4.3 on soil sampling.
• In the text portion of the published soil survey, find the complete description of your soil types, including its drainage and other characteristics, and their consequences for agriculture, forestry and other land uses.

Adapted from How to use Soil Surveys and Aerials Photos in Logging Operations, by Jim Ochterski, full text in resource box below.