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Describing Soil Profiles

An open soil pit will be available for students to observe the soil profile. In general, the soil will be described and evaluated according to the guidelines and procedures outlined in Extension Circular 406R - Land Judging for Farms and Homesites (http://www.wvu.edu/%7Eagexten/landrec/judging/index.html). Students should study this circular and be familiar with the following sections: (1) Definition of Soil Characteristics, (2) Limiting Factors, and (3) Factors Affecting Suitability. In addition, students should be able to determine slope by using a clinometer, soil color by using Munsell Color Charts, soil texture by the feel method, and soil structure from pit observations. The following boxes describe the agents that give soil its colors and provide some information regarding use of the Munsell Soil Color Chart.

Coloring Agents

Gray colors will exist in soils that are not well drained. These gray colors are developed by the reduction and movement of iron in wet areas of the soil. As iron moves, the reddish or brownish color disappears, leaving behind gray colors. In general, these spots of gray color are called mottles.

Soil Color

The hue is determined by the numbers and letters in the upper right-hand corner of the page. The page given above represents hue 10YR. Most soils in West Virginia have hues of 10YR. The value is represented by the numbers given on the left side of the page, and they are read vertically. Chroma is given across the bottom of the page and is read horizontally. So, an example of a proper Munsell designation is 10YR 5/6. Students should refer to the Soil Survey of Lewis County to determine how these colors are used in profile descriptions.

Reading Colors

Soil texture is defined as the relative proportion of sand, silt, and clay. Particle sizes for each fraction are as follows:
  1. 1. Rock Fragments >2 mm
  2. Sand 2 - 0.05 mm
  3. Silt 0.05 - 0.002 mm
  4. Clay < 0.002 mm
Soil texture is important because it affects:
  1. Water-holding capacity
  2. Ability to store nutrients
  3. Movement of water into and through the soil (pollutant leaching potential)
  4. Erodibility
  5. Shrink-swell potential

Soil texture will be determined in the field by the feel method. Texture classes in the United States are represented by the texture triangle presented below. Flowcharts to assist in determining texture can be found at: http://cmase.pbworks.com/f/Soil+Texture+By+Feel.pdf.

Additional information may be found at:



Texture Triangle

Soil structure is defined as the combination or arrangement of primary particles into secondary units called peds. Soil structure is important because it affects water infiltration and movement through the soil, heat transfer, and aeration. Additions of organic matter will improve soil structure.

Types of structure in soils include granular, blocky, prismatic, columnar, and platy. Soils without a specific type of structure are called structureless and may be single grain or massive.

Additional information may be found at:




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