Soil Characterization Protocols:

A Step by Step GuideField Analysis

Introduction

o We Study Soil Because It's A... o Soil Forming Factors o Soil Characterization o Characterization and Sampling Options

Instruments for Field Analysis

o Instruments for digging the pit or hole and conducting initial horizon identification

o Instruments for conducting Bulk Density and field protocols

o Instruments for recording data about soil profile

o Preparing for the field

 

Finding and Describing Horizons

o Soil Pit Technique o Exposed Profile (Road Cut) Technique o Auger Technique o Surface Sample Technique

Horizon Properties

o Soil Structure o Soil Color

Munsell Notation Hue Value Chroma

o Soil Consistence o Soil Texture part 1 o Soil Texture part 2 o Soil Texture part 3 o Soil Texture part 4 o Presence of Roots and Rocks

o Test for Free Carbonates

Soil Sampling

o Taking Bulk Density Samples Using the Soil Pit or Other Exposed Soil Profile

o Taking Bulk Density Samples Using the Soil Pit or Other Exposed Soil Profile, part 2

o Taking Bulk Density Samples Using the Auger Method

o Taking Bulk Density Samples Using the Auger Method, part 2

o Taking Bulk Density Samples Using the Surface Sample Method

o If You Are Not Taking Bulk Density Samples and Using the Soil Pit or Other Exposed Road Cut Profile

o If You Are Not Taking Bulk Density Samples and Using the Auger Method

o If You Are Not Taking Bulk Density Samples and Using the Surface Sample Method

Final Analysis Conclusion

o When You Are Finished Sampling

Laboratory Analysis

Characterization Laboratory Analysis

o Introduction

Instruments for Laboratory Analysis

o Drying and Sieving o Testing for Bulk Density o Testing for Particle-Size Distribution o Testing for pH o Testing for Soil Fertility

Laboratory Analysis Protocols

o Measuring Bulk Density and Preparing Samples for Other Lab Analyses

o Determining the Volume of Any Rocks That Are in a Sample

o Preparing Samples for Other Lab Analyses (If

You Are Not Measuring Bulk Density) o Particle-Size Distribution, part 1 o Particle-Size Distribution, part 2 o Particle-Size Distribution, part 3 o Particle-Size Distribution, part 4 o Particle-Size Distribution, part 5 o Particle-Size Distribution, part 6 o Particle-Size Distribution, part 7 o Making Sense of the Particle-Size Distribution

Measurements, part 1 o Making Sense of the Particle-Size Distribution

Measurements, part 2 o pH Measurements o Soil Fertility: Introduction   o Soil Fertility: Preparation and Extraction o Soil Fertility: Nitrate Nitrogen (N) o Soil Fertility: Phosphorus (P) o Soil Fertility: Potassium (K) o Soil Particle Density: Introduction o Soil Particle Density: Introduction part 2 o Soil Particle Density: Introduction and

comparision between bulk density and particle density

o Soil Particle Density, part 1 o Soil Particle Density, part 2

o Soil Particle Density, part 3

We Study Soil Because It's A(n)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 FactorsParent Material

Climate

Topography

Biota

(The first four factors over) Time 

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 of different soil profiles.

Horizon Properties

Soil CharacterizationSoil CharacterizationFollowing 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

Field measurements are done once at each site

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

Soil Sampling

Characterization and Sampling Options

Soil Pit

Dig 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.

Exposed Profile (road cut) Use a road cut, excavation site, or other location where the top 1 meter of soil has been exposed.

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.

Finding and Describing Horizons

Instruments for Field Analysis:

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.)

 

Soil Sampling

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

1. Starting from top, observe profile to determine properties and differences between horizons.

2. Place golf tee or marker at the top and bottom of each horizon to clearly identify it.

3. 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 climate soil in New Mexico, USA

Forest soil in Florida, USA

Finding and Describing Horizons

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.

Expose a fresh soil face.

Follow Soil Pit Technique directions.

Finding and Describing Horizons

Auger Technique1. Identify an area where you can dig four holes where the soil profiles should be similar.

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

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:

4. Identify each horizon and measure its thickness using the depth of the auger hole.

Finding and Describing Horizons

Surface Sample TechniqueIn 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.

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

Horizon Properties

Soil StructureSoil structure is the shape that the soil takes based on its physical and chemical properties. Each individual unit of soil structure is called a ped. Take a sample of undisturbed soil in your hand (either from the pit or from the shovel or auger). Look closely at the soil in your hand and examine its structure. Possible choices of soil structure are:

Granular: Resembles cookie crumbs and is usually less than 0.5 cm in diameter. Commonly found in surface horizons where roots have been growing.

Blocky: Irregular blocks that are usually 1.5 - 5.0 cm in diameter.

Prismatic: Vertical columns of soil that might be a number of cm long. Usually found in lower horizons.

Columnar: Vertical columns of soil that have a salt "cap" at the top. Found in soils of arid climates.

Platy: Thin, flat plates of soil that lie horizontally. Usually found in compacted soil.

Single Grained: Soil is broken into individual particles that do not stick together. Always accompanies a loose consistence. Commonly found in sandy soils.

Massive: Soil has no visible structure, is hard to break apart and appears in very large clods.

If you wish download the protocol above so that you can use it in the field, here are pict files soil texture page 2.

Below are some images of the different soil structures.

With Structure:

Granular Blocky

Prismatic Columnar

Platy

Structureless:

Single grained Massive

Horizon Properties

Soil Color

1. Take a ped of soil from each horizon and note on the data sheet whether it is moist, dry or wet. If it is dry, moisten it slightly with water from your water bottle.

2. Break the ped

3. Stand with the sun over your shoulder so that sunlight shines on the color chart and the soil sample you are examining.

 

Note: Sometimes, a soil sample may have more than one color. Record a maximum of two colors if necessary, and indicate (1) the Main (dominant color) and (2) the Other (sub-dominant color).

Horizon Properties

Soil ColorMunsell Notation

The Munsell code below each color in the GLOBE color chart is a universal notation that describes the soils' color.

Horizon Properties

Soil Color (continued)

Munsell Notation

The Munsell code below each color in the GLOBE color chart is a universal notation that describes the soils' color.

Chroma

The number after the slash is the Chroma. Chroma describes how the "intensity" of a color. Colors of low chroma values are sometimes called weak, while those of high chroma are said to be highly saturated, strong, or vivid. the scale starts at zero, for neutral colors, but there is no arbitrary end to the scale.

Horizon Properties

Soil Color (continued)

Munsell Notation

The Munsell code below each color in the GLOBE color chart is a universal notation that describes the soils' color.

Hue

The first set of number and letter symbols represents the hue. Hue represents the position of the color on the color wheel (Y=Yellow, R=Red, G=Green, B=Blue, YR=Yellow Red, RY=Red Yellow).

Horizon Properties

Soil Color (continued)

Munsell Notation

The Munsell code below each color in the GLOBE color chart is a universal notation that describes the soils' color.

Value

The number before the slash is the Value. Value indicates the lightness of a color. The scale of value ranges from 0 for pure black to 10 for pure white.

Horizon Properties

Soil ConsistenceTake a ped from the top soil horizon. If the soil is very dry, moisten the face of the profile using a water bottle with a squirt top and then remove a ped to determine consistence.

(Repeat this procedure for each horizon in your profile.)

Holding it between your thumb and forefinger, gently squeeze the ped until it pops or falls apart. Record one of the following categories of soil consistence on the data sheet.

Loose

You have trouble picking out a single ped and the structure falls apart before you handle it.*

 

FriableThe ped breaks with a small amount of

* Soils with "single grained" structure always have loose consistence.

pressure.

 

 

FirmThe ped breaks when you apply a good amount of pressure and dents your fingers before it breaks.

Extremely FirmThe ped can't be crushed with your fingers (you need a hammer!).

Horizon Properties

Soil Texture

The way a soil "feels" is called the soil texture.

Soil texture depends on the amount of each size of particle in the soil.

Sand, silt, and clay are names that describe the size of individual particles in the soil.

Sand are the largest particles and they feel "gritty."

Silt are medium sized, and they feel soft, silky or "floury."

Clay are the smallest sized particles, and they feel "sticky" and they are hard to squeeze.

Relative Size Comparison of Soil ParticlesBarrel  

Plate

Silt(feels floury)

(0.05 - 0.002 mm, USDA) (0.02 - 0.002 mm, ISSS)

 Coin

Clay(feels

sticky)

(< 0.002 mm, USDA) (<

Sand(feels gritty)

(2.00 - 0.05 mm, USDA) (2.00 - 0.02 mm, ISSS)

  

0.002 mm, ISSS)

Horizon Properties

Soil Texture (continued)To Determine Soil Texture

Step 1 (Get and moisten sample) Use the triangle to determine the soil texture of your horizon.  Place some soil from a horizon (about the size of a small egg) in your hand, and, using the spray mist bottle, moisten the soil. Let the water soak in and then work the soil between your fingers until it is the same moisture throughout. Once the soil is moist, try to form a ball. If the soil forms a ball, go on to Step 2. If the soil does not form a ball, go to Step 5.

Step 2 (Test for Clay)

A. If the soil:

o Is really sticky o Hard to squeeze o Stains your hands o Has a shine when rubbed o Forms a long ribbon (5+ cm) without

breaking,

Call it a clay and go to Step 3. Otherwise, go to B.

C. If the soil is: o Soft o Smooth o Easy to squeeze,  o At most slightly sticky, o Forms a short ribbon (less than 2 cm) 

Call it a loam and go to Step 3.  Otherwise, go to D.

D. If the soil forms a ball but no ribbon, go to Step 4.  

B. If the soil:  o Is somewhat sticky o Is somewhat hard to squeeze  o Forms a medium ribbon (between 2-5 cm)

Call it a clay loam and go to Step 3.  Otherwise, go to C.

Horizon Properties

Soil Texture (continued)To Determine Soil Texture

Step 3 (Refine initial soil texture classification from Step 2 for relative amounts of sand and silt) Wet a small pinch of the soil in your palm and rub it with a forefinger.

If the soil:

Feels very gritty, go to E Feels very smooth, with no grittyfeeling,

go to F

Feels only a little gritty, go to G

E. Add the word sandy to the initial classification.

Soil texture is (check one):

sandy clay, sandy clay loam, sandy loam

Soil Texture is complete.  

F. Add the word silt or silty to the initial G. Leave the original classification of (check

classification.

Soil texture is (check one):

silty clay, silty clay loam, silt loam

Soil Texture is complete.

Soil Texture is complete.  

one): clay, clay loam, loam

Soil Texture is complete.

Horizon Properties

Soil Texture (continued)To Determine Soil Texture

Step 4 (Test for loamy sand or silt) If the soil: Forms a ball Forms no ribbon And is

H. Very gritty

Soil texture is:

loamy sand

Soil Texture is complete.

Or

I. Very soft and smooth with no gritty feeling,

Soil texture is: silt

Soil Texture is complete.

Step 5 (Test for sand) If the soil: Forms no ball and falls apart in your hand,

Soil texture is: sand

Soil Texture is complete.

Horizon Properties

Presence of Roots and Rocks

Presence of RootsObserve and record if there are none, few, or many roots in the horizon.

Presence of RocksObserve and record if there are none, few, or many rocks* in the horizon.

* A rock is defined as being larger than 2 mm in size.

Horizon Properties

Test For Free CarbonatesFree carbonates are compounds that coat soil particles. They form under certain conditions such as in dry climates where the pH is above 7. They are also found in some soil profiles that have parent materials made of carbonates (such as limestone).

This test is performed by squirting vinegar on the soil. If free carbonates are present, they will "effervesce" or bubble when the vinegar reacts with them. Record one of the following based on your observation:

None: you observe no reaction (the soil has no free carbonates).

Slight: you observe a slight amount of bubbling (the soil is coated with some carbonates).

Strong: you observe a strong reaction (many bubbles) (the soil has many carbonate coatings present).

Soil Sampling

Taking Bulk Density Samples

If you are using a Soil Pit or other Exposed Soil Profile

(road cut)1. For each horizon in your soil profile, push a can with a known volume into the side of the horizon. If necessary, wet the soil first so that the can will go in easily. Stop when you can see some of the soil poking through the small hole in the bottom of the can. (Remember, you will collect three samples from each horizon in your profile.)

 

2. If it is still difficult to push the can into the soil, you may need to place a piece of wood over the can and hit the wood with the hammer to spread the force of the hammer blow to all edges of the can at once and to minimize denting the can.Note: Some denting is allowed in the procedure, but if the can dents too badly, consider taking a bulk density sample using the auger method for dense, hard, or rocky horizons.

Soil Sampling

Taking Bulk Density Samples

If you are using a Soil Pit or other Exposed Soil Profile

(road cut)3. Using a trowel or shovel, remove the can and the soil surrounding it. Trim the soil from around the can until it is flat against the edges of the can so that the volume of the soil is the same as the volume of the can.

 

4. Cover the labeled can with the lid or other cover and return it to the classroom.

 

5. Repeat this procedure so that you have three bulk

 

density samples for each horizon.

6. Weigh each sample in its can and record this moist weight on the Bulk Density Data Work Sheet.

 

7. Remove the covers. Place the samples in the soil drying oven until the soils are dry.

 

Soil Sampling

Taking Bulk Density Samples

If you are using the auger method

 1. Auger to a depth of 1 or 2 cm past the top of the horizon to be sampled.* * Use the depths from the first soil profile you withdrew with the auger as a guide.

 

2. Use the auger to remove a sample of the horizon. If the horizon is thinner than the length of the auger head, partially turn the auger so that the whole sample will be from one horizon. Do not turn the auger more than one complete circle (360°) so that the soil does

not become compacted.

3. Measure the diameter of the hole the auger made.

 

4. Measure the depth of the hole the auger made.

Soil Sampling

Taking Bulk Density Samples

If you are using the auger method

5. Once the sample is removed, transfer all the soil from the auger head into a sample container without losing any on the ground.

 

6. Repeat steps 1-5 for each horizon in the soil profile, for a total of three profiles.

 

7. Cover or seal the samples in labeled containers and transport them to the classroom.

8. Weigh each sample in its can and record this moist weight on the Bulk Density

 

Data Work Sheet.

9. Place the samples in the soil drying oven (be sure the covers are removed) until the samples are dry.

 

Soil Sampling

Taking Bulk Density Samples

If you are using the surface sample method

1. Choose three locations close to where you performed your soil characterization protocol and remove vegetation and other material from the soil surface.

2. At each location, push a can with a known volume into the surface of the soil. If necessary, wet the soil so that the can will go in easily. Stop when you can see some soil poking through the small hole in the bottom of the can.

3. If it is difficult to push the can into the soil, place a piece of wood over the can and hit the wood with the hammer to spread the force of the hammer blow to all edges of the can at once.

Soil Sampling

If You Are Not Taking Bulk Density Samples

If you are using a Soil Pit or other Exposed Soil Profile (road cut)

1. Dig a large sample from each soil horizon. Avoid the area of the soil face that was tested for carbonates and avoid touching the soil samples so that you pH measurements will not be contaminated.

2. Place each sample in a bag or other soil container.

3. Label each bag with the site name, horizon name, and top and bottom depths.

4. Bring these samples in from the field.

5. Spread the samples on separate plastic plates or sheets of newspaper to dry in the air.

Soil Sampling

If You Are Not Taking Bulk Density Samples

If you are using the Auger Technique

1. Auger to a depth of 1 or 2 cm past the top of the horizon to be sampled. If the horizon is thinner than the length of the auger head, partially turn the auger so that the whole sample will be from one horizon.

2. Place the sample in a labeled bag or other soil conainer. Avoid touching the sample and contaminating it.

3. Bring these samples in from the field, and spread them on separate plastic plates or sheets of newspaper to dry in the air.

Soil Sampling

If You Are Not Taking Bulk Density Samples

If you are using the Surface Sample Method

1. Dig three large samples from the soil surface. Avoid the area of the soil face that was tested for carbonates and avoid touching the soil samples so that you pH measurements will not be contaminated.

2. Place each sample in a bag or other soil container.

3. Label each bag with the site name and top and bottom depths.

4. Bring these samples in from the field, and spread them on separate plastic plates or sheets of newspaper to dry in the air.

Field Analysis Conclusion

When You Are Finished Sampling

1. Photograph the face of the pit, or the soil profile you have removed and placed on the ground with the auger.

Place a tape measure along the profile (in the pit or next to the auger sample profile you created) so that 0 cm is at the top of the profile to record horizon depths for the picture.

Take another photograph of the landscape outside the pit or around the auger hole.

Send these photographs to: the GLOBE Student Data Archive at the address given in the Teacher's Guide, or if they were taken with a digital camera, submit them to the GLOBE Student Data Archive

electronically.