Soil Lab
Prelab
1. Define the following:
a. Porosity: space for air or liquids (pores)
b. Permeability: ability of water to pass through soil
c. Water holding capacity: ability of soil to hold water (inversely related to porosity)
d. Solution: molecuels dissolved in a solvent
e. Suspension: particles transported in water
2. What industries would find it important to know the structure of the soil? agriculture, construction, mining/minerals
3. Using what you know about North Carolina now, would large scale use of septic tanks work well? No clay has permeability.
4. Use the soil triangle to decide what type of soil the following are.
a. 10% Clay, 60% Sand, and 30% Silt sandy loam
b. 60% Clay, 20% Sand, and 20% Silt clay
c. 20% Clay, 20% Sand, and 60% Silt silt loam
d. 20% Clay, 40% Sand, and 40% Silt loam
a. Porosity: space for air or liquids (pores)
b. Permeability: ability of water to pass through soil
c. Water holding capacity: ability of soil to hold water (inversely related to porosity)
d. Solution: molecuels dissolved in a solvent
e. Suspension: particles transported in water
2. What industries would find it important to know the structure of the soil? agriculture, construction, mining/minerals
3. Using what you know about North Carolina now, would large scale use of septic tanks work well? No clay has permeability.
4. Use the soil triangle to decide what type of soil the following are.
a. 10% Clay, 60% Sand, and 30% Silt sandy loam
b. 60% Clay, 20% Sand, and 20% Silt clay
c. 20% Clay, 20% Sand, and 60% Silt silt loam
d. 20% Clay, 40% Sand, and 40% Silt loam
Lab
Problem: What is the texture, waterholding capacity, and permeability of the soil samples?
Hypotheses: The soil sample will be mostly clay. The pebbles will be more permeable than the sand.
Hypotheses: The soil sample will be mostly clay. The pebbles will be more permeable than the sand.
IV: soil composition
DV: permeability
CV: amount of water, amount of soil, size of containers
DV: permeability
CV: amount of water, amount of soil, size of containers
Objectives
After this lab you should be able to do the following:
● Determine soil texture and judge cohesive and adhesive soil properties.
● Determine capillary action and waterholding capacity of soil.
● Determine dry and wet permeability of soil.
Materials
Spray Bottles
3 Plastic Cups
Rulers
Wax Marker
Soil Analysis Card
Bag of Sand
Bag of Clay
Soil Sample
Tap Water
4 Plastic Cylinders
4 Plastic Vials
4 Plastic Cups
Cheesecloth
Rubber Bands
60cc plastic medicine cups
humus
scissors
balance
Clock with Second Hand
Twist Ties
Procedure
1. Using the soil assigned to your group, follow the directions to classify the type of soil you have. Then, record the results in the table below, including the percentages of each type of soil.
After this lab you should be able to do the following:
● Determine soil texture and judge cohesive and adhesive soil properties.
● Determine capillary action and waterholding capacity of soil.
● Determine dry and wet permeability of soil.
Materials
Spray Bottles
3 Plastic Cups
Rulers
Wax Marker
Soil Analysis Card
Bag of Sand
Bag of Clay
Soil Sample
Tap Water
4 Plastic Cylinders
4 Plastic Vials
4 Plastic Cups
Cheesecloth
Rubber Bands
60cc plastic medicine cups
humus
scissors
balance
Clock with Second Hand
Twist Ties
Procedure
1. Using the soil assigned to your group, follow the directions to classify the type of soil you have. Then, record the results in the table below, including the percentages of each type of soil.
Hydrologic Soil Analysis
1. Using a mortar and pestle, crush enough soil to fill about 1/3 of the jar provided.
2. Remove any pieces of rock larger than about 2mm (between 1/16” & 1/8”).
3. Put the soil into the jar and fill it with water, leaving about an inch of space at the
top, and put the lid on the jar.
4. Shake the jar for a couple minutes.
5. Allow the contents of the jar to settle.
6. After about a minute, put a line at the top of the sediment that settled first. This is
sand.
7. After a couple hours put a mark at the top of the sediment that settled next
(someone from the group will have to come back later to do this). This is silt.
8. After two days mark the top of the last later of sediment. This is clay (it will
probably not all settle, some of it can float in there for many days.)
9. Measure the total height of the sediment in the jar in cm. Measure the thickness of
the sand, silt and clay layers and calculate the percentage of each. Record these
measurements in the table below.
10. Make sure to include a picture of your final results.
11. Use the soil triangle to determine the type of soil you have. Compare this to what
you determined by feel.
1. Using a mortar and pestle, crush enough soil to fill about 1/3 of the jar provided.
2. Remove any pieces of rock larger than about 2mm (between 1/16” & 1/8”).
3. Put the soil into the jar and fill it with water, leaving about an inch of space at the
top, and put the lid on the jar.
4. Shake the jar for a couple minutes.
5. Allow the contents of the jar to settle.
6. After about a minute, put a line at the top of the sediment that settled first. This is
sand.
7. After a couple hours put a mark at the top of the sediment that settled next
(someone from the group will have to come back later to do this). This is silt.
8. After two days mark the top of the last later of sediment. This is clay (it will
probably not all settle, some of it can float in there for many days.)
9. Measure the total height of the sediment in the jar in cm. Measure the thickness of
the sand, silt and clay layers and calculate the percentage of each. Record these
measurements in the table below.
10. Make sure to include a picture of your final results.
11. Use the soil triangle to determine the type of soil you have. Compare this to what
you determined by feel.
Determination of Permeability
1. Suspend the soil column about 1 inch above a beaker.
2. Put 100mL of water into a graduated. Designate one member as the timekeeper
and one as the recorder. When everyone is ready, pour the water onto the wet
sand. The timer should time how long it takes until the first drop of water comes out
of the bottom of the column. Set up a data table to record this information. Watch
the column until there is not more water standing above the soil and no more
dripping through the column. Record this time as well.
3. Repeat with the pebbles column.
1. Suspend the soil column about 1 inch above a beaker.
2. Put 100mL of water into a graduated. Designate one member as the timekeeper
and one as the recorder. When everyone is ready, pour the water onto the wet
sand. The timer should time how long it takes until the first drop of water comes out
of the bottom of the column. Set up a data table to record this information. Watch
the column until there is not more water standing above the soil and no more
dripping through the column. Record this time as well.
3. Repeat with the pebbles column.
Questions
1. Considering all the samples analyzed by your class in the first three parts, do you find any relationship between texture and composition? Texture usually gets close to determining composition, but the hydrologic test proves more specific when finding composition.
2. Compare and contrast the texture analyzed by feel and hydrologically. How do your results compare? Explain any discrepancies. Silt and sand varied widely while amount of clay came close. There were some problems with communication when conducting the feel test, such as not knowing exactly what "ribbons" meant.
3. Do you believe one type of soil composition test (by feel or with water) is more reliable than the other? Explain your answer. I believe the hydrologic test was more reliable because there was less room for human error. It was based on quantitative knowledge more than qualitative knowledge.
3. How might the composition of soil affect the growth of plants? Think about wet and dry conditions. More permeable soil would allow water to get through to the roots. Soil that gets waterlogged easily would cause a problem for nutrients. The best soil for plants would allow water to reach the roots, but not too much water.
5. What characteristic of soil is most important in determining water holding capacity? Permeability.
6. Imagine a sloping field of very sandy soil and a sloping field of soil with a very high clay content, each with an identical drainage ditch at the bottom. In a prolonged heavy downpour, do you think one ditch will be more likely to flood then the other? Why? The ditch at the bottom of the clay hill will be more likely to flood because sand would hold the water while clay would let it flow down.
7. If you have two fields of crops, one in which the soil was mostly sand and the other mostly clay, which would you have to water most often and why? You would have to water the mostly clay field most often because it would use up or dry out the water supply more frequently.
8. Use the information you have collected about the local soil samples and suggest how this would affect agriculture and building in the area. The soil with more clay would be better for building. Loamy soil, like the sample our group examined, would be best for agriculture because it nourishes plants the best.
1. Considering all the samples analyzed by your class in the first three parts, do you find any relationship between texture and composition? Texture usually gets close to determining composition, but the hydrologic test proves more specific when finding composition.
2. Compare and contrast the texture analyzed by feel and hydrologically. How do your results compare? Explain any discrepancies. Silt and sand varied widely while amount of clay came close. There were some problems with communication when conducting the feel test, such as not knowing exactly what "ribbons" meant.
3. Do you believe one type of soil composition test (by feel or with water) is more reliable than the other? Explain your answer. I believe the hydrologic test was more reliable because there was less room for human error. It was based on quantitative knowledge more than qualitative knowledge.
3. How might the composition of soil affect the growth of plants? Think about wet and dry conditions. More permeable soil would allow water to get through to the roots. Soil that gets waterlogged easily would cause a problem for nutrients. The best soil for plants would allow water to reach the roots, but not too much water.
5. What characteristic of soil is most important in determining water holding capacity? Permeability.
6. Imagine a sloping field of very sandy soil and a sloping field of soil with a very high clay content, each with an identical drainage ditch at the bottom. In a prolonged heavy downpour, do you think one ditch will be more likely to flood then the other? Why? The ditch at the bottom of the clay hill will be more likely to flood because sand would hold the water while clay would let it flow down.
7. If you have two fields of crops, one in which the soil was mostly sand and the other mostly clay, which would you have to water most often and why? You would have to water the mostly clay field most often because it would use up or dry out the water supply more frequently.
8. Use the information you have collected about the local soil samples and suggest how this would affect agriculture and building in the area. The soil with more clay would be better for building. Loamy soil, like the sample our group examined, would be best for agriculture because it nourishes plants the best.
General Conclusions
Evaluation of Hypothesis: The first hypothesis about the soil sample composition was invalid because our sample had more silt and sand than clay. The other hypothesis about permeability was correct because the pebbles allowed water to flow through while the sand just held it.
Accuracy: There was a lot of opinion used in this lab, especially when doing the "feel" test. This presents opportunity for human bias and error to stand in the way of results. Also, some soil samples contained leaf litter, which interfered with accurate results about the soil itself.
Real-Life Application: Knowing the soil composition of an area is important when considering how much water to apply and which crops to plant there. In some instances when amount of water and type of plant is not controlled, it can interfere with the soil and the nutrients it holds. At Narragansett Bay, many plants and animals are being disrupted because the nutrients in the soil are encountering problems (Ferguson). Erosion is rampant, soil not staying in place and destroying plant life. If the soil were less permeable, this might not have been as bad.
Works Cited
Ferguson, Wenley. "Climate Change Impacts Bay's Salt Marshes." EcoRI News. N.p., n.d. Web. 21 Apr. 2013.
Accuracy: There was a lot of opinion used in this lab, especially when doing the "feel" test. This presents opportunity for human bias and error to stand in the way of results. Also, some soil samples contained leaf litter, which interfered with accurate results about the soil itself.
Real-Life Application: Knowing the soil composition of an area is important when considering how much water to apply and which crops to plant there. In some instances when amount of water and type of plant is not controlled, it can interfere with the soil and the nutrients it holds. At Narragansett Bay, many plants and animals are being disrupted because the nutrients in the soil are encountering problems (Ferguson). Erosion is rampant, soil not staying in place and destroying plant life. If the soil were less permeable, this might not have been as bad.
Works Cited
Ferguson, Wenley. "Climate Change Impacts Bay's Salt Marshes." EcoRI News. N.p., n.d. Web. 21 Apr. 2013.