Soil Lab
Partners: Paula Escobar, Ryan Pate
Pre Lab
1. Define the following:
a. Porosity- the state or quality of being porous.
b. Permeability – the property or state of being permeable.
c. Water holding capacity - the specific ability of a particular type of soil to hold water against the force of gravity.
d. Solution – a molecular mixture of two different substances.
e. Suspension - the state in which the particles of a substance are mixed with a fluid but are un-dissolved.
2. What industries would find it important to know the structure of the soil? The forestry and agriculture industries find it important to know the structure of the soil because soil plays a major part in their business and if the soil does not have a good structure then their whole industry can go down. As well as the construction industry because without knowing the type of soil below the biulding you dont know how stable the building will be because if the soil moves underneath it it will come tumbling down.
3. Using what you know about North Carolina now, would large scale use of septic tanks work well? No, large scale use of septic tanks would not work well because North Carolina’s soil is not very permeable so if this method was used then it could leak and create a potential health hazard. As well as it wouldnt work because the water would not filtrate through the soil and cleanse itself further it would just sit and become stagnant pool, a prime breeding place for bacteria.
a. Porosity- the state or quality of being porous.
b. Permeability – the property or state of being permeable.
c. Water holding capacity - the specific ability of a particular type of soil to hold water against the force of gravity.
d. Solution – a molecular mixture of two different substances.
e. Suspension - the state in which the particles of a substance are mixed with a fluid but are un-dissolved.
2. What industries would find it important to know the structure of the soil? The forestry and agriculture industries find it important to know the structure of the soil because soil plays a major part in their business and if the soil does not have a good structure then their whole industry can go down. As well as the construction industry because without knowing the type of soil below the biulding you dont know how stable the building will be because if the soil moves underneath it it will come tumbling down.
3. Using what you know about North Carolina now, would large scale use of septic tanks work well? No, large scale use of septic tanks would not work well because North Carolina’s soil is not very permeable so if this method was used then it could leak and create a potential health hazard. As well as it wouldnt work because the water would not filtrate through the soil and cleanse itself further it would just sit and become stagnant pool, a prime breeding place for bacteria.
Problem
A) Permeability Test: Which type of sediment will have the greatest permeability?
B) pH Test: What is the pH of local soil?
B) pH Test: What is the pH of local soil?
Hypothesis
A) Permeability Test: The gravel will be more permeable than the sand.
B) pH Test: The pH of local soil is neither acidic or basic.
B) pH Test: The pH of local soil is neither acidic or basic.
Materials
- Soil sample
- Water
- Glass Jar with lid
- Sand
- Gravel
- Permeability Tube (2)
- Stop Watch
- Beaker
- Graduated Cylinder
- pH paper
- Petri Dish
- Marker
- Mortar and pestle
- Ruler
Procedure
A) Permeability Test:
- Fill up the permeability tube to the 6cm mark with gravel.
- Put 50mL of water in a graduated cylinder.
- Pour the water into the tube. Start timing when the water hits the sediment.
- Stop timing when the water flowing out of the bottom of the tube has slower to a drip.
- Empty the tube and repeat with sand, then a mixture of both sand and gravel.
- Put some soil in a petri dish. Add some distilled water to make a muddy slurry.
- Use the pH paper to determine the pH of the soil.
C) Soil Texture
- Follow the directions on the chart below.
D) Soil Composition by Settling
- Crush enough soil to fill about 1/3 of the jar.
- Remove any pieces of rock larger than about 2mm (between 1/16" and 1/8")
- 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.
- Shake the jar for a couple minutes and then set it to settle.
- After about a minute put a line at the top of the sediment that settled first. THIS IS SAND.
- After a couple hours put a mark at the top of the sediment that settled next. THIS IS SILT.
- After two days or so mark the top of the last later of sediment. THIS IS CLAY. (Not all of it will settle, some of it will still be floating around.)
- 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.
- Use the soil triangle to determine the type of soil you have. Compare this to what you determined by feel.
Observations and Pictures
The soil that was used in the experiment was from the Leaf Litter Lab so it was a lot older and a lot more dry compared to the soils other groups in the class did. When the pH test was performed the pH turned out to be 7 which is neutral meaning its neither basic or acidic just like it was predicted in the hypothesis. When the permeability tests were performed the gravel was the most permeable which also supported the hypothesis that was made. The results from determining soil by texture yielded the results that our soil was loam. After the soil was left in the jar for a couple of days to settle the percentage of clay silt and sand was recorded in the following results:
- Silt - 1.7 cm - 30%
- Sand - 3.8 cm - 66%
- Clay - .2 cm - 4%
Graphs and Tables
Analysis and Conclusion
- 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
- Given what you saw relative to particle size and permeability, explain any relationship you think there is between texture and permeability? The larger the particles the more permeable it is. An example of this is clay, when you shape it and form it you can feel nothing but the solid surface and it is has very little permeability. The antithesis of this is something like sand or gravel, you can feel the individual particles of these and they are very permeable.
- How might the consistence of soil affect the growth of plants? Think about wet and dry conditions. In dry conditions the roots of the plant constrict the pore space limiting the amount of water, air, and nutrients that can get to the roots. In contrast, in wet conditions the roots do not constrict the soil in an attempt to find water and therefore the pore space remains and the flow of water, air, and nutrients is unchanged and the growth of the plant continues.
- How did the determination of soil texture compare for the two tests you did? Were they close? Completely different? The soil tests we did were similar. For the first test we determined that the soil was loam by using the Soil Texture by Feel Flow Chart and for the second we determined that soil was sandy loam by using the Soil Composition by Settling method. There’s one key difference between them and it’s the fact that one contains more sand making it more permeable.
- What characteristic of soil is most important in determining water holding capacity? Particle size is the most important in determining water holding capacity because it determines the amount of pore space there is for the water to travel between the particles.
- 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? Yes, the clay will be more likely to flood because less of the water will filtrate through the clay soil and flow down the hill into the drainage ditch. On the sandy hill the water will be able to filtrate into the soil before reaching the drainage ditch or at least it is more likely to.
- If you have two field 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? The sand soil will have to be watered more often because the water will filtrate through the soil into the aquifer quicker than it would with clay soil.
General Analysis and Conclusion
Use the information you have collected and researched about your local soil samples and suggest how this would affect agriculture in the area.
The information that was collected showed that the soil around the creek in the back of Heritage High School is sandy loam which contains a majority of sand with 30% silt and 4% clay. From this information we can tell that the soil is very permeable and will be well suited for agriculture. Our soil was a month old however which could have altered the results a little bit. However, we can conclude that because the soil is composed of mostly sand and silt it allows a lot water, air, and nutrients to pass through which would be very beneficial if the land was to be used for agriculture.
Hypothesis Evaluation: Both of the hypothesis turned out to be correct. The gravel was a lot more permeable than sand, and the difference was almost 43 seconds, because the gravel was a lot more permeable it also recovered 19 mL more water than sand did. Also, the pH was 7 which is neither acidic or basic just like it was predicted in the hypothesis.
Accuracy of Results: The results for our group specifically were not accurate enough because the soil we used came from the Leaf Litter Lab which was about a month old. If more recent soil was used we might have gotten different results in the pH experiment and the soil texture. Our soil was too dry and it interfered with our soil texture by feel experiment because the soil would not stick together unless there was a lot of it and so it had to be redone a couple of times. Also when the soil is left without moisture for a long time like a week without water or just moisture from dew it can greatly change the permeability of the soil because the pore space was shrunk by the drying up of the soil.
Application: Through this experiment I have learned about the importance of soil and how it affects the agriculture in an area. Soils that separate easily are a lot more permeable for example sand and gravel unlike soils that stay close together such as clay. The permeability of soil is important to agriculture in an area when they are trying to grow crops because it determines the amount of water flow and nutrients to the roots of plants or crops. I also learned that agricultural industries are not the only ones who find it important to know the structure of soil. Other industries such as construction, civil engineering, underground utilities, etc., also need to know about soil structure.
Real Life Example: Healthy soil is extremely important for the environment because it allows for more crops and plants to grow in turn increasing biodiversity in the area. Surprisingly, forest fires are beneficial when trying to improve soil health. Forest fires help maintain the earths nitrogen cycle therefore releasing more nitrogen into the soil and the soil becomes more fertile.Without nitrogen plants would be unable to survive and the results showed that artificial fertilizers and pesticides in fact damage the earths nitrogen cycle and deplete the amount of nitrogen released into the soil, so forest fires are a natural and a lot more beneficial way of trying to enhance plant growth in an area.
Benson, Jonathan. "Forest fires are beneficial to soil health." Natural News.com. Natural News Network, 11 Aug. 2010. Web. 17 Apr. 2013. <http://www.naturalnews.com/029429_forest_fires_nitrogen.html>.
The information that was collected showed that the soil around the creek in the back of Heritage High School is sandy loam which contains a majority of sand with 30% silt and 4% clay. From this information we can tell that the soil is very permeable and will be well suited for agriculture. Our soil was a month old however which could have altered the results a little bit. However, we can conclude that because the soil is composed of mostly sand and silt it allows a lot water, air, and nutrients to pass through which would be very beneficial if the land was to be used for agriculture.
Hypothesis Evaluation: Both of the hypothesis turned out to be correct. The gravel was a lot more permeable than sand, and the difference was almost 43 seconds, because the gravel was a lot more permeable it also recovered 19 mL more water than sand did. Also, the pH was 7 which is neither acidic or basic just like it was predicted in the hypothesis.
Accuracy of Results: The results for our group specifically were not accurate enough because the soil we used came from the Leaf Litter Lab which was about a month old. If more recent soil was used we might have gotten different results in the pH experiment and the soil texture. Our soil was too dry and it interfered with our soil texture by feel experiment because the soil would not stick together unless there was a lot of it and so it had to be redone a couple of times. Also when the soil is left without moisture for a long time like a week without water or just moisture from dew it can greatly change the permeability of the soil because the pore space was shrunk by the drying up of the soil.
Application: Through this experiment I have learned about the importance of soil and how it affects the agriculture in an area. Soils that separate easily are a lot more permeable for example sand and gravel unlike soils that stay close together such as clay. The permeability of soil is important to agriculture in an area when they are trying to grow crops because it determines the amount of water flow and nutrients to the roots of plants or crops. I also learned that agricultural industries are not the only ones who find it important to know the structure of soil. Other industries such as construction, civil engineering, underground utilities, etc., also need to know about soil structure.
Real Life Example: Healthy soil is extremely important for the environment because it allows for more crops and plants to grow in turn increasing biodiversity in the area. Surprisingly, forest fires are beneficial when trying to improve soil health. Forest fires help maintain the earths nitrogen cycle therefore releasing more nitrogen into the soil and the soil becomes more fertile.Without nitrogen plants would be unable to survive and the results showed that artificial fertilizers and pesticides in fact damage the earths nitrogen cycle and deplete the amount of nitrogen released into the soil, so forest fires are a natural and a lot more beneficial way of trying to enhance plant growth in an area.
Benson, Jonathan. "Forest fires are beneficial to soil health." Natural News.com. Natural News Network, 11 Aug. 2010. Web. 17 Apr. 2013. <http://www.naturalnews.com/029429_forest_fires_nitrogen.html>.