Guide, part 1: Soil Characterization

Soil Characterization Protocols

A Step by Step Guide Field Analysis

Introduction

We Study Soil Because It's A...

  • Great integrator
  • Medium of crop production
  • Filter of water and wastes
  • Producer and absorber of gases
  • Home to organisms (plants, animals and others)
  • Medium for plant growth
  • Snapshot of geologic, climatic, biological, and human history
  • Source material for construction, medicine, art, etc.
  • Essential natural resource
  • Waste decomposer

 

Horizon Properties

Soil Forming Factors

  • Parent Material
  • Climate
  • Topography
  • Biota
  • (The first four factors over) Time

soil profile image

These five factors work together to create a unique soil profile made of layers called horizons.

For GLOBE Soil Characterization, we will describe, sample and analyze the soils from horizons.

 

Soil Characterization

Following this protocol, you and your students will:

  1. expose the top 1 meter of soil
  2. describe the exposed soil profile
  3. take samples of each soil horizon
  4. prepare soil samples for lab analyses
  5. analyze the soil samples in the lab
  6. review the data to understand your soil better
  7. submit the data to GLOBE

Sample at least two sites.

1. Near the Soil Moisture study site 2. Within the Biology study site
moisture site
bio site

Field measurements are done once at each site

Three replicate samples from each horizon are taken and reported one time for each site.

3 cans

Soil Sampling

Characterization and Sampling Options

Soil Pit Exposed Profile (road cut)
soil pitDig a soil pit at least 1 meter deep and as big around as is necessary to easily observe all of the soil horizons from the bottom to the top of the pit.

road cut

Use a road cut, excavation site, or other location where the top 1 meter of soil has been exposed.
Auger Surface Sample
auger
Use an auger to remove soil samples to a depth of 1 meter.

surface sample
Use a garden trowel or shovel to sample only the top 10 cm of soil, if digging to a depth of 1 meter is not possible.

Instruments for Field Analysis

field instruments

    Digging pit or hole

      Shovel or Auger Trowels

    Laying out profile

      Plastic Tarp or Trash Bag

    Marking horizons

      Nails, Golf Tees, or other tool for marking horizon boundary marker

    Measuring depth of profile

      Meter Stick

    Moistening profile face

      Squirt bottles

    General use

      Paper Towels

Instruments for Field Analysis 2

more field instruments

Instruments for conducting Bulk Density and field protocols

    Soil sampling for lab protocols

      4 Liter (1 Gallon) size Ziplock Bags or Containers

    Bulk Density

      Sampling Cans Wood Block and Hammer

    Soil color

      Soil Color Book

    Free Carbonate test

      Vinegar in acid bottle

    Study site slope

      Clinometer (You may use the clinometer that you made for the Land cover/Biology protocol.)

more field instruments

Instruments for recording data about soil profile

    Field protocol information

      Soil Characterization Information Sheet

    Data recording

      Soil Characterization and Bulk Density Data Entry Sheets Water Proof Marker and Pencils

    Soil Profile photograph

      Camera

soil rocks students image

Preparing for the Field

    1. Fill acid bottle with vinegar

    2. Fill squirt bottles with water

    3. Make a clinometer (see Land Cover/Biology Protocol)

    4. Collect bulk density containers

      For Pit, Exposed Profile, and Surface Sample Method

        a. find can weight

        b. find can volume by filling the can with water, pouring the water into a graduated cylinder, and reading the amount in mL.

        c. label cans

        d. hammer hole in bottom

      For Auger Method

        a. label the containers

 

Finding and Describing Horizons
Soil Pit Technique

 

First, obtain permission to dig a pit. Obey any and all safety precautions requested, and ask about power and water lines.

 

    • Starting from top, observe profile to determine properties and differences between horizons.
    • Place golf tee or marker at the top and bottom of each horizon to clearly identify it.
    • Look for: different colors, shapes, roots, the size and amount of stones, small dark nodules (called concretions), worms, or other small animals and insects, worm channels, and anything else that is noticeable.

arid soil profile

Arid climate soil in New Mexico, USA

 

spodosol

Forest soil in Florida, USA

 

Exposed Profile (Road Cut) Technique

First, obtain permission to take samples from the road cut, excavation, or other soil profile exposed by others. Obey any and all safety precautions requested. Ask about power and water lines.

Road cut

    Expose a fresh soil face.

Scraping wall of pit with trowel

    Follow Soil Pit Technique directions.

 

 

Auger Technique

1. Identify an area where you can dig four holes where the soil profiles should be similar.

Trees
2. Spread a plastic bag, tarp, board, or other surface on the ground next to where you will dig your first hole.

Making an auger hole 1 meter in depth
3. Assemble a profile of the top 1 meter of the soil by removing successive samples with the auger and laying them end-to-end as follows:

Laying out auger profile
4. Identify each horizon and measure its thickness using the depth of the auger hole.
Measuring hole depth

Surface Sample Technique

 

In situations where it is not possible to expose the top meter of soil, another option is to use the top 10 cm of soil as a horizon sample for soil characterization.
1. Use a garden trowel or shovel to carefully remove the top 10 cm of soil from a small area and set it on the ground.

10 cm surface sample
2. Treat this sample as a horizon and proceed to characterize its properties.

Soil in shovel

 Continue to part 2 of the Step-by-Step Guide: Horizon Properties.