Pre-Lab Questions
1. Define the following:
Porosity – the ability of a substance to absorb liquids.
Permeability – the quality of a substance that allows fluids or gases to pass through it.
Water holding capacity – amount of water that is available to plants in the soil.
Solution – a homogenous mixture of two substances.
Suspension – when small particles of a substance are dispersed throughout a gas or liquid.
2. What industries would find it important to know the structure of the soil?
The industries of agriculture, mining, construction, logging, and archeology would all find it important to know the structure of soil.
3. Using what you know about North Carolina now, would large scale use of septic tanks work well?
No, I don’t think the large scale use of septic tanks would work well at all. Generally, from my experience, the soil of North Carolina is primarily clay and not very permeable. If these large scale septic tanks were put into effect, I think it would not be broken down correctly and begin to ooze out of the ground.
Porosity – the ability of a substance to absorb liquids.
Permeability – the quality of a substance that allows fluids or gases to pass through it.
Water holding capacity – amount of water that is available to plants in the soil.
Solution – a homogenous mixture of two substances.
Suspension – when small particles of a substance are dispersed throughout a gas or liquid.
2. What industries would find it important to know the structure of the soil?
The industries of agriculture, mining, construction, logging, and archeology would all find it important to know the structure of soil.
3. Using what you know about North Carolina now, would large scale use of septic tanks work well?
No, I don’t think the large scale use of septic tanks would work well at all. Generally, from my experience, the soil of North Carolina is primarily clay and not very permeable. If these large scale septic tanks were put into effect, I think it would not be broken down correctly and begin to ooze out of the ground.
Hypothesis
If different tests are done to the different samples of soil, then the collected soil will be a sandy clay loam composition, a pH of 7 and not very permeable.
Variables
Independent Variable: The soil used in the various test
Dependent Variable: The composition, pH, and the permeability of the different types of soil.
Controlled Variable: pH strip used, set up for permeability test
Control: Topsoil & Sand provided
Experimental: The soil collected from our yards
Dependent Variable: The composition, pH, and the permeability of the different types of soil.
Controlled Variable: pH strip used, set up for permeability test
Control: Topsoil & Sand provided
Experimental: The soil collected from our yards
Problem
What is the composition, pH, and permeability of the collected soil.
Materials
Soil
Sand
Gravel
Glass Jar
Petri Dish
Marker
pH strips
permeability tube
ring stand
beaker
stopwatch
graduated cylinder
Sand
Gravel
Glass Jar
Petri Dish
Marker
pH strips
permeability tube
ring stand
beaker
stopwatch
graduated cylinder
Procedure
1. The first test is to determine the composition of the soil. First place a handful of the soil that needs to be tested in someone’s hand.
2. Moisten the soil. Follow the flow chart by answering the yes and no questions to determine the composition of the soil.
3. The pH test is performed by initially placing the soil being tested into a Petri dish.
4. Add water to the soil to create a mixture of water and soil.
5. Place the pH strip into the soil mixture and use the chart provided on the pH package to determine the pH of the soil.
6. The permeability test is done by initially setting up the cup on the stand so it is 1 inch above the beaker collecting the water.
7. Place 50 mL into a graduated cylinder.
8. Place the soil into the cup suspended into the stand and place a beaker below the cup to catch the water.
9. Pour the 50 mL of water that was in the graduated cylinder into the cup with the soil and begin timing as soon as water reaches the soil.
10. Continue to time until water comes through the soil and into the beaker. Measure the amount of water that was released into the beaker.
2. Moisten the soil. Follow the flow chart by answering the yes and no questions to determine the composition of the soil.
3. The pH test is performed by initially placing the soil being tested into a Petri dish.
4. Add water to the soil to create a mixture of water and soil.
5. Place the pH strip into the soil mixture and use the chart provided on the pH package to determine the pH of the soil.
6. The permeability test is done by initially setting up the cup on the stand so it is 1 inch above the beaker collecting the water.
7. Place 50 mL into a graduated cylinder.
8. Place the soil into the cup suspended into the stand and place a beaker below the cup to catch the water.
9. Pour the 50 mL of water that was in the graduated cylinder into the cup with the soil and begin timing as soon as water reaches the soil.
10. Continue to time until water comes through the soil and into the beaker. Measure the amount of water that was released into the beaker.
Observations
Permeability Test
- The item with the highest permeability (gravel) also had the lowest flow time and the highest amount of water recovered
- The item with the highest permeability (gravel) also had the lowest flow time and the highest amount of water recovered
pH Test
- The pH of the soil ended up being a 6, which is very close to my hypothesis. I predicted that the soil would be the most neutral rating on the scale, which would be a 7; however, the soil were more acidic than I thought.
- The pH of the soil ended up being a 6, which is very close to my hypothesis. I predicted that the soil would be the most neutral rating on the scale, which would be a 7; however, the soil were more acidic than I thought.
Determining Soil Texture Test
- By hand, we determined that the soil was a Sandy Clay Loam
- When testing the soil components through letting it settle in a jar, we determined that the soil was a Sandy Loam. Therefore, there was not as much clay as we thought.
- By hand, we determined that the soil was a Sandy Clay Loam
- When testing the soil components through letting it settle in a jar, we determined that the soil was a Sandy Loam. Therefore, there was not as much clay as we thought.
Analysis Questions
1. Use the soil triangle to decide what type of soil the following are.
10% Clay, 60% Sand, and 30% Silt – Sandy Loam
60% Clay, 20% Sand, and 20% Silt - Clay
20% Clay, 20% Sand, and 60% Silt – Silt Loam
20% Clay, 40% Sand, and 40% Silt – Loam
2. Given what you saw relative to particle size and permeability, explain any relationship you think there is between texture and permeability?
Usually, the finer the soil texture, the slower the permeability. For example, out of silt, sand, and clay, sand has the largest particle size and the grittiest texture because of that. Sand also has the largest permeability because of that because it's large particles allows it to have higher porosity and, therefore, let water through the best. Clay, for example, would have the least permeability out of the group. Clay is squishy to touch and not gritty at all in texture. Clay's particles are very small so they do not let a lot of water through; therefore, clay would have the lowest permeability.
3. How might the consistence of soil affect the growth of plants? Think about wet and dry conditions.
The consistence of soil affects the growth of plants by determining how much moisture is able to reach the plants roots. Soil that has a consistency of primarily clay will not be able to distribute an adequate amount of water to the plant. Clay has a very high water holding capacity and an extremely slow permeability. The water would get absorbed in the clay and not reach the roots. Soil that has a consistency leaning more towards sand and silt are much better suited to growing plants as more water can flow through the soil at a faster rate reaching the roots. In dry conditions, it is even more crucial for plants to receive adequate water. The consistency needs to be able to supply the plant with water by having an acceptable permeability.
4. How did the determination of soil texture compare for the two tests you did? Were they close? Completely different?
When determining the soil texture by hand, we concluded that we had a sandy clay loam soil; however, after finishing the jar test to determine it's texture, we realized that it was more of a sandy loam. These results are very close because sandy clay loam and sandy loam lie adjacent to one another on the soil triangle. Unfortunately, we thought that there was more clay in the soil than there really was. This is unusual, because the North Carolina area is known for the amount of clay in it's soil.
5. What characteristic of soil is most important in determining water holding capacity?
The composition of the soil is the most important in determining the water holding capacity. Clay generally has a much higher water holding capacity than that of silt or sand because the particle size of the clay is much smaller allowing much less water to escape. Sand, in comparison, has very large particles which creates space that the water very easily flows out of.
6. Imagine a sloping field of very sandy soil and a sloping field of soil with 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?
I think the sandy soil would be much less likely to flood than the clay soil. This is primarily because of the sandy soil’s permeability. Water flows much faster through sandy soil than it does through clay soil. The water would flow into the sandy soil and into the earth, thus, flooding more slowly. The clay soil would accumulate water much faster as the water would take much longer to flow through the soil.
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 sandy soil most often. The sandy soil has a much lower water holding capacity than the clay soil. The sandy soil, therefore, wouldn’t hold as much water than the clay soil would so you’d need to water the clay soil more often to be sure the plants get a sufficient amount of water. This isn’t as much of a problem in the clay soil because the clay naturally holds more water.
10% Clay, 60% Sand, and 30% Silt – Sandy Loam
60% Clay, 20% Sand, and 20% Silt - Clay
20% Clay, 20% Sand, and 60% Silt – Silt Loam
20% Clay, 40% Sand, and 40% Silt – Loam
2. Given what you saw relative to particle size and permeability, explain any relationship you think there is between texture and permeability?
Usually, the finer the soil texture, the slower the permeability. For example, out of silt, sand, and clay, sand has the largest particle size and the grittiest texture because of that. Sand also has the largest permeability because of that because it's large particles allows it to have higher porosity and, therefore, let water through the best. Clay, for example, would have the least permeability out of the group. Clay is squishy to touch and not gritty at all in texture. Clay's particles are very small so they do not let a lot of water through; therefore, clay would have the lowest permeability.
3. How might the consistence of soil affect the growth of plants? Think about wet and dry conditions.
The consistence of soil affects the growth of plants by determining how much moisture is able to reach the plants roots. Soil that has a consistency of primarily clay will not be able to distribute an adequate amount of water to the plant. Clay has a very high water holding capacity and an extremely slow permeability. The water would get absorbed in the clay and not reach the roots. Soil that has a consistency leaning more towards sand and silt are much better suited to growing plants as more water can flow through the soil at a faster rate reaching the roots. In dry conditions, it is even more crucial for plants to receive adequate water. The consistency needs to be able to supply the plant with water by having an acceptable permeability.
4. How did the determination of soil texture compare for the two tests you did? Were they close? Completely different?
When determining the soil texture by hand, we concluded that we had a sandy clay loam soil; however, after finishing the jar test to determine it's texture, we realized that it was more of a sandy loam. These results are very close because sandy clay loam and sandy loam lie adjacent to one another on the soil triangle. Unfortunately, we thought that there was more clay in the soil than there really was. This is unusual, because the North Carolina area is known for the amount of clay in it's soil.
5. What characteristic of soil is most important in determining water holding capacity?
The composition of the soil is the most important in determining the water holding capacity. Clay generally has a much higher water holding capacity than that of silt or sand because the particle size of the clay is much smaller allowing much less water to escape. Sand, in comparison, has very large particles which creates space that the water very easily flows out of.
6. Imagine a sloping field of very sandy soil and a sloping field of soil with 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?
I think the sandy soil would be much less likely to flood than the clay soil. This is primarily because of the sandy soil’s permeability. Water flows much faster through sandy soil than it does through clay soil. The water would flow into the sandy soil and into the earth, thus, flooding more slowly. The clay soil would accumulate water much faster as the water would take much longer to flow through the soil.
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 sandy soil most often. The sandy soil has a much lower water holding capacity than the clay soil. The sandy soil, therefore, wouldn’t hold as much water than the clay soil would so you’d need to water the clay soil more often to be sure the plants get a sufficient amount of water. This isn’t as much of a problem in the clay soil because the clay naturally holds more water.
General Conclusions
Use the information you have collected and research about your local soil samples and suggest how this would affect agriculture in your area
Based on the information, the local soil in the area is primarily clay based (Although my particular soil sample didn't). Agriculture has both positives and negatives to having clay soil. The primary positive to having clay soil is that it holds moisture very well; however, the nature of clay makes roots very hard to grow and also causes very slow draining. The soil is also very slow to rise in temperature in the spring. Building a foundation on the soil has
both its positives and negatives as well. An advantage is that it is relatively cheap compared to other common foundation material; however, water leakage and damage as well as pressure buildups are common issues that can plague construction.
Based on the information, the local soil in the area is primarily clay based (Although my particular soil sample didn't). Agriculture has both positives and negatives to having clay soil. The primary positive to having clay soil is that it holds moisture very well; however, the nature of clay makes roots very hard to grow and also causes very slow draining. The soil is also very slow to rise in temperature in the spring. Building a foundation on the soil has
both its positives and negatives as well. An advantage is that it is relatively cheap compared to other common foundation material; however, water leakage and damage as well as pressure buildups are common issues that can plague construction.
Conclusion
My hypothesis was partly correct in some aspects, but incorrect in other aspects. The predictions for the soil compositions were generally correct. The hand test showed the soil to be sandy clay loam; however, the soil had less clay than we expected and it proved to really be a similar composition of sandy loam. The predictions for the pH were close, but not entirely accurate. It was predicted that the pH would be neutral, 7, for each of the soils; however, the pH turned out to be slightly acidic for each soil being around a pH of 6. The predications for the permeability were generally accurate. Clay had the slowest permeability because clay particle size is extremely small and allows very little water to escape. Sand had a much faster permeability than clay. This is because the particles of sand are much larger and allowed more space for the water to escape.
This experiment’s results were generally accurate; however, there were potential sources of error present. One source of error was the test to determine the soil’s composition. The chart was not particularly descriptive which made determining the composition fairly easy to make a mistake and come to the wrong conclusion about the soil quality. This was also the only test to determine soil composition so the composition may not be entirely accurate. When recording the permeability, only one trial was done. Having multiple trials and taking an average would enhance the lab in yielding a more accurate permeability.
This lab has many applications that can be applied in the real world, particularly in the subject of agriculture and construction. Knowing the soil composition of the ground allows agriculture to be much more successful. This lab proved that certain soil compositions retain more water than others. For example, clay retains much more water than that of sandy soil. This would be useful to know as knowing how much water to give a plant can be crucial to its growth. Being able to know just the soil’s composition allows the agriculture industry and recreational gardeners to grow plants at a much higher success rate. Knowing the soil is also crucial in the field of construction. Construction companies rely on knowing what type of soil they are building on as it could potentially be the difference between a safe and unsafe building. Clay also yields weathering problems pressure building which makes it crucial to these construction companies to know what soil they are building on.
This experiment’s results were generally accurate; however, there were potential sources of error present. One source of error was the test to determine the soil’s composition. The chart was not particularly descriptive which made determining the composition fairly easy to make a mistake and come to the wrong conclusion about the soil quality. This was also the only test to determine soil composition so the composition may not be entirely accurate. When recording the permeability, only one trial was done. Having multiple trials and taking an average would enhance the lab in yielding a more accurate permeability.
This lab has many applications that can be applied in the real world, particularly in the subject of agriculture and construction. Knowing the soil composition of the ground allows agriculture to be much more successful. This lab proved that certain soil compositions retain more water than others. For example, clay retains much more water than that of sandy soil. This would be useful to know as knowing how much water to give a plant can be crucial to its growth. Being able to know just the soil’s composition allows the agriculture industry and recreational gardeners to grow plants at a much higher success rate. Knowing the soil is also crucial in the field of construction. Construction companies rely on knowing what type of soil they are building on as it could potentially be the difference between a safe and unsafe building. Clay also yields weathering problems pressure building which makes it crucial to these construction companies to know what soil they are building on.
Works Cited
"Soil Composition and Formation." Soil Composition and Formation. N.p., n.d. Web. 18 April. 2013. http://www.nerrs.noaa.gov/doc/siteprofile/acebasin/html/envicond/soil/slform.htm.