Soil Surveys: How-To

For erosion insight and trail grades see this page 

USDA Web Soil Survey- find your soil type on an interactive USDA soil map

4 DIY soil survey methods

How do you know what’s in your trail site soil horizon? By taking samples and testing them:

METHOD 1: the Ribbon Test

Roll a handful of moist soil into a tube shape with both hands. Squeeze it between your thumb and forefinger to form the longest and thinnest ribbon possible.

Texture Feel Ribbon
Sand Grainy Can’t form a ribbon
Loam Soft with some graininess Thick and very short
Silt Floury Makes flakes rather than a ribbon
Sandy Clay Substantial graininess Thin, fairly long—50 to 76 mm (2 to 3 inches)—holds its own weight
Clay Smooth Very thin and very long—76 mm (3 inches)

The tread surface should match the inte

METHOD 2: USDA guide to texture by feel (shown below the horizons)

Soil_profileSoilHorizons

First let me say that trail tread should be on the subsoil/mineral soil B and/or parent rock C, or bedrock R, a little A is OK. O should be removed during construction if it exists (in desert climates it may be very thin or non-existent). Enough use can start to displace O depending on its depth and user numbers. This approach however, can create a trough, and a berm that won’t allow water to escape the trail. It’s best to remove O and the outside berm as well to establish outslope that will allow water to sheet flow off the trail, not down it.

soil-particle-size3METHOD 3: Mason Jar Method (link to protocol)

soil-particle-sizesoil-particle-size2

625px-SoilTexture_USDA1) Divide the layer type depth or thickness by the total depth or thickness 2) multiply by 100 to find the percentages 3) locate the soil type in the chart to the left using the percentages

 

 

 

 

 

 

 

METHOD 4: 

areforum.org/USCS.pdf

UNIFIED SOIL CLASSIFICATION SYSTEM: FIELD METHOD

METHOD 5:

  1. LABORATORY CLASSIFICATION OF SOILS FOR ENGINEERING PURPOSES
  2. uta.edu
  3. scribd.com/document/Sieve-Analysis

 

Additional info:

 

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