Collaborators:
Devin Stafford, Paige Carmen, Parker Savage, Emily Smith, Parker Smith, Alec Kondichook
Introduction and Problem:
Throughout Earth's history soil erosion has been a naturally occurring process and is responsible for creating some of the most majestic landscapes on Earth; however, human intervention hastens these changes by obstructing soil formation, making erosion a serious ecological issue. The problem with erosion is bifold — overall soil health is threatened and nearby water sources become susceptible to pollution by valuable plant nutrients. The effects of this ecological problem can be seen at a local scale. Due to a growing population, the town of Wake Forest along with the city of Raleigh demand increased crop yields from local farms and more land for housing, which inescapably disrupts the land and exacerbates erosion. Thus, the North Carolina Sedimentation Control Law plays a major role by regulating construction, building and other land-disturbing activities. This law “prohibits visible off-site sedimentation from construction sites but permits the owner and developer to determine the most economical, effective methods for erosion and sedimentation control” (North Carolina Sedimentation Control Law). Ground cover has been proven to be the most effective method in that it intercepts rainfall to alleviate the annihilation of soil structure, and disrupts run-off water to give it more time to infiltrate and to allow deposition of sediment. Therefore, ground cover is crucial in “preserving the productive value of soil and sustaining the quality of the waters that receives the sediment”(Lang, Des and McDonald, G. Warren). Yet, not all types of ground cover have the same equal ability to reduce the risk of erosion, which is why it is important to determine the most effective ground cover when it comes to stimulating soil health, plant growth and water quality. For this reason, the question and problem that will be addressed throughout this experiment is, "How does the presence and amount of ground cover affect the level of erosion that occurs in an environment?"
Hypothesis:
If three samples of soil - one with no ground cover, the second with 10% ground cover, and third with 90% ground cover - are exposed to flowing water the one with the most grass cover will have the least amount of erosion as the soil is better protected by plant cover, while the bare soil with no ground cover will have the most erosion due to the lack of protection provided by ground cover.
Parts of an Experiment:
Materials:
Methods and Procedure:
A. Sowing the seeds
Devin Stafford, Paige Carmen, Parker Savage, Emily Smith, Parker Smith, Alec Kondichook
Introduction and Problem:
Throughout Earth's history soil erosion has been a naturally occurring process and is responsible for creating some of the most majestic landscapes on Earth; however, human intervention hastens these changes by obstructing soil formation, making erosion a serious ecological issue. The problem with erosion is bifold — overall soil health is threatened and nearby water sources become susceptible to pollution by valuable plant nutrients. The effects of this ecological problem can be seen at a local scale. Due to a growing population, the town of Wake Forest along with the city of Raleigh demand increased crop yields from local farms and more land for housing, which inescapably disrupts the land and exacerbates erosion. Thus, the North Carolina Sedimentation Control Law plays a major role by regulating construction, building and other land-disturbing activities. This law “prohibits visible off-site sedimentation from construction sites but permits the owner and developer to determine the most economical, effective methods for erosion and sedimentation control” (North Carolina Sedimentation Control Law). Ground cover has been proven to be the most effective method in that it intercepts rainfall to alleviate the annihilation of soil structure, and disrupts run-off water to give it more time to infiltrate and to allow deposition of sediment. Therefore, ground cover is crucial in “preserving the productive value of soil and sustaining the quality of the waters that receives the sediment”(Lang, Des and McDonald, G. Warren). Yet, not all types of ground cover have the same equal ability to reduce the risk of erosion, which is why it is important to determine the most effective ground cover when it comes to stimulating soil health, plant growth and water quality. For this reason, the question and problem that will be addressed throughout this experiment is, "How does the presence and amount of ground cover affect the level of erosion that occurs in an environment?"
Hypothesis:
If three samples of soil - one with no ground cover, the second with 10% ground cover, and third with 90% ground cover - are exposed to flowing water the one with the most grass cover will have the least amount of erosion as the soil is better protected by plant cover, while the bare soil with no ground cover will have the most erosion due to the lack of protection provided by ground cover.
Parts of an Experiment:
- Independent Variable: Type of ground cover (10% grass and 90% grass)
- Dependent Variable: Amount of water collected in mL and how much soil erodes.
- Controlled Variables: potting mix, 2 liter bottles, amount of soil, number of grass seeds, amount of sunlight, H2O quality, even elevated surface, beakers, amount of time grown.
- Control Group: 2 liter bottle with soil only.
- Experimental Groups: 2 - 2 liter bottles with soil and grown grass scattered amongst the area.
Materials:
- Potting Mix
- Three 2 liter bottles cut in half
- Three 250 mL beakers
- Grass seed
- Elevated surface to hold the bottles
- Tap water
Methods and Procedure:
A. Sowing the seeds
- Place soil in an empty, cut out 2L bottle (see photo 2). Spread grass seed evenly throughout the soil.
- Water grass seeds every 3-5 days for 20 days and allow it to sit near a source of sunlight.
- After the allotted growing time has ended, you are ready to test the effects of the two grass-filled bottles.
- Fill one more empty 2L bottle with soil and leave alone to test as a control group.
- Take each bottle and elevate it evenly with the previous bottle for most accurate results. Place an empty beaker underneath the mouth of the bottle to allow flow of water.
- Obtain three separate beakers with 200 mL of water.
- Pour the beakers in at the top of the bottle away from the mouth and let the water erode the soil and pour out of the mouth and into the empty beaker.
- Repeat steps 4 and 5 for each of the remaining samples of soil with some grass and lots of grass.
- Record how much soil eroded (per inch) once the soil settles at the bottom of the beaker.
- Record characteristics and distinctions of each individual sample - water quality before and after & any errors.
- Answer the conclusion questions.
Photographs:
Images courtesy of: Alec Kondichook, Emily Smith, and Devin Stafford |
Data:
Bottle Water Collection (mL) Amount of Soil Eroded (mm) Qualitative Observations
No Water/Soil Only 150 mL 4 mm clear and brownish water
10% Grass 250 mL 5 mm very dark water with lots of soil
90% Grass 200 mL 10 mm only soil from riparian area, dark water
_________________________________________________________________________________________________________________________________________________
Analysis:
Three samples of soils - one with no ground cover, the second with 10% ground cover and the third with 90% ground cover - were placed in 2 liter bottles and their ability to mitigate soil erosion was tested by pouring the same amount of water (600 mL) into each sample bottle. After organizing the data using a table, some questions arose as it became evident that the 90% ground cover was not as effective as we'd hoped for minimizing soil erosion. Rather, our assumptions of how the water would effect each sample individually were quite the opposite. Although the amount of water collected was greater for the samples of soil with grass, the quality of the water did not supported the fact that plant cover is effective for runoff and erosion control. While the bare soil yielded a water mix with high turbidity and larger particles of soil, the sample with no grass managed to retain the sediments better by impeding surface run-off and thus yielding a clearer water mix. These qualitative observations are conveyed by picture 10-12, where the sample with only soil is picture 10 and the samples with 10% and 90% grass cover are pictures 11 and 12. The sample with 10% grass caused a large amount of water to be collected (250 mL), but it dramatically increased soil erosion, as did the 90% grass sample. The quality of the water observed for this sample's mixture could be attributed to the aforementioned factors. The other 10% grass cover missing from the 90% grass sample is directly known as a "riparian area". This area right near the mouth of the bottle was not covered by any grass whatsoever, which caused a skew in data. As the water began to flow, our observations concluded that this sample was infiltrating the water as we hoped it to do but, soon after, the riparian area with no grass cover eroded and 10mm of soil eroded. Without this significant factor, our data would be completely turned upside down, as the water quality would have possibly improved along with the amount of soil eroding would decline.
Conclusion:
The hypothesis — "If three samples of soil - one with no ground cover, the second with 10% ground cover, and third with 90% ground cover - are exposed to flowing water the one with the most grass cover will have the least amount of erosion as the soil is better protected by plant cover, while the bare soil with no ground cover will have the most erosion due to the lack of protection provided by ground cover" — was somewhat validated by the results of this experiment, but also aroused a few questions. Such questions include: Why was water collection greater for other samples than others? What was the cause for the increased soil erosion? What do the qualitative observations have to say about the hypothesis? It is captivating to note some discrepancies in the data, which at first could only be attributed to possible errors in the actual experiment. The fact that the potting mix was able to retain the most water out of all three samples without the help of ground cover was astounding. It was expected that the lack of plant roots to absorb water would cause the sample without ground cover (control) to absorb the least amount of water; however, the data shows that this did not happen. The data reveals that the control absorbed more water than the samples of soil with grass, 50 mL and 100 mL more to be exact, based off of how much water was collected. This was later attributed to the fact that the soil with 90% plant cover had a riparian area surrounding the mouth of the bottle where the flow of water exited. In addition, it was later determined that potting soil is created to "absorb water quickly and retain up to two times its own weight in water" (Balcony Container Gardening). Therefore, the potting soil was able to retain the most amount of water even without the presence of ground cover. Despite these observations, the group's hypothesis was not completely invalidated. The water collected from the control sample proved that soil without ground cover is at a greater risk of erosion; it had larger soil particles and somewhat high turbidity. Without plant cover to impede run-off water and facilitate the deposition of sediment, the "soil particles [in the potting soil] can be more easily eroded once they become saturated" (Rudd, P. J). It would certainly aid to prohibit these inconsistencies if all samples of soil used in the experiment had equal water holding capacity. The potting soil used for bottle one (control) and bottle three (90%) proved to be more successful in a sense that it allowed the grass to grow taller and thicker while it was also able to absorb more water than bottle two (10%), which had a much different soil type that could most nearly be compared to mulch. Because of this, the data could most definitely be skewed in some way, shape, or form. Furthermore, while it was evident that ground cover can effectively protect soil from eroding, certain areas of the ecosystem with no ground cover can have major ecological impacts on water quality and soil health. The riparian area demonstrated in sample 3 caused a great amount of soil to erode as the water flowed. Before this area eroded, it was observed that the water quality was much greater than that of the other two samples, and more water was infiltrating through the roots of the grass and into the beaker.
The results of this experiment emphasize the importance of plant cover in preventing soil erosion. This is not an attempt to belittle the role of other types of ground cover. However, the data from this experiment shows that vegetation is the most crucial cover to promote soil health, plant growth, and water condition. After deforestation, planting grass seed would create a long-term solution to various ecological issues. It would reduce soil erosion by obstructing the impact of raindrops on the soil surface, and more importantly by slowing run-off water to give it more time to infiltrate and to allow deposition of deposit. It is also very important to determine the plant type that will be used. Selecting plant species should be done only after considering the climate, soil and grazing regime of a community so that they will persist, and effectively prevent soil erosion. Water filtration ties ties into the ability of run-off to be slowed by the soil's ground cover. Since the sample with grass slows water run-off, it offers the greatest chance of water filtration. In addition, this ground cover creates barriers that allow sediment in the run-off water to be quickly deposited, meaning that valuable plant nutrients are less likely to pollute nearby rivers and streams, and instead can be deposited in the soil to galvanize plant growth.
Overall, this lab demonstrates the importance of maintaining good ground cover over soil. This is further supported by experiments conducted on a bigger scale. For example, Peter Rudd used a rainfall simulator to demonstrate that ground cover effectively protected the soil by "delaying the start of runoff, reducing the rate of runoff was reduced, reducing the amount of runoff, and reducing the amount of silt in the runoff water" (Rudd, P.J). Moreover, the Hubbard Brook Experiment centered on how deforestation affects nutrient cycles in a larger ecosystem. The control group consisted of the loss of water and nutrients form an uncut forest ecosystem, which would be used to compare to the loss in one that was stripped of its trees. V-shaped concrete dams were built across the creeks, and anchored by impervious bedrock, so that all surface water leaving could be measured along with its dissolved nutrient content. The results showed that when deforestation occurred, water runoff increased. "With no plants to help absorb and retain water, the amount of water flowing out of the deforested valley increased by 30-40%" (Landscape Maintenance - Causes of Erosion). Consequently, soil erosion increased, which caused a large increase in the outflow of nutrients from the ecosystem. This demonstrates that deforestation is a disastrous process; it results in a degraded environment with reduced biodiversity and reduced ecological services. The harmful effects of deforestation can only be hindered if efforts are made to ensure that soil has adequate ground cover that will improve its ability to prevent soil erosion.
Citation(s):
"Landscape Maintenance - Causes of Erosion." Causes of Erosion. Landscape Planet, n.d. Web. 02 Nov. 2014. <http://www.landscapeplanet.com/maintenance-1-cause-of-erosion.htm>.
Lang, Des, and McDonald, G. Warren. Maintaining Groundcover to Reduce Erosion and Sustain Production. Tamworth: NSW Department of Primary Industries, 14 Jan. 2005. PDF.
North Carolina Sedimentation Control Law. N.p.: Web. 2 Nov. 2014. NC Department of Environment and Natural Resources, n.d. PDF.
Rudd, P. J. "EFFECT OF GROUND COVER AND REDUCED CULTIVATION ON RUNOFF AND EROSION." The Archives of the Rare Fruit Council of Australia. N.p., Sept. 1987. Web. 02 Nov. 2014. <http://rfcarchives.org.au/Next/CaringForTrees/GroundCoverSoilLoss9-87.htm>.
"Soil Erosion and Degradation." WorldWildlife.org. World Wildlife Fund, n.d. Web. 09 Mar. 2015. <https://www.worldwildlife.org/threats/soil-erosion-and-degradation>.
"What Is Potting Soil?" Balcony Container Gardening. N.p., n.d. Web. 06 Nov. 2014.<http://www.balconycontainergardening.com/gardening/147-what-is-potting-soil>.
By: Noah Nelson
Bottle Water Collection (mL) Amount of Soil Eroded (mm) Qualitative Observations
No Water/Soil Only 150 mL 4 mm clear and brownish water
10% Grass 250 mL 5 mm very dark water with lots of soil
90% Grass 200 mL 10 mm only soil from riparian area, dark water
_________________________________________________________________________________________________________________________________________________
Analysis:
Three samples of soils - one with no ground cover, the second with 10% ground cover and the third with 90% ground cover - were placed in 2 liter bottles and their ability to mitigate soil erosion was tested by pouring the same amount of water (600 mL) into each sample bottle. After organizing the data using a table, some questions arose as it became evident that the 90% ground cover was not as effective as we'd hoped for minimizing soil erosion. Rather, our assumptions of how the water would effect each sample individually were quite the opposite. Although the amount of water collected was greater for the samples of soil with grass, the quality of the water did not supported the fact that plant cover is effective for runoff and erosion control. While the bare soil yielded a water mix with high turbidity and larger particles of soil, the sample with no grass managed to retain the sediments better by impeding surface run-off and thus yielding a clearer water mix. These qualitative observations are conveyed by picture 10-12, where the sample with only soil is picture 10 and the samples with 10% and 90% grass cover are pictures 11 and 12. The sample with 10% grass caused a large amount of water to be collected (250 mL), but it dramatically increased soil erosion, as did the 90% grass sample. The quality of the water observed for this sample's mixture could be attributed to the aforementioned factors. The other 10% grass cover missing from the 90% grass sample is directly known as a "riparian area". This area right near the mouth of the bottle was not covered by any grass whatsoever, which caused a skew in data. As the water began to flow, our observations concluded that this sample was infiltrating the water as we hoped it to do but, soon after, the riparian area with no grass cover eroded and 10mm of soil eroded. Without this significant factor, our data would be completely turned upside down, as the water quality would have possibly improved along with the amount of soil eroding would decline.
Conclusion:
The hypothesis — "If three samples of soil - one with no ground cover, the second with 10% ground cover, and third with 90% ground cover - are exposed to flowing water the one with the most grass cover will have the least amount of erosion as the soil is better protected by plant cover, while the bare soil with no ground cover will have the most erosion due to the lack of protection provided by ground cover" — was somewhat validated by the results of this experiment, but also aroused a few questions. Such questions include: Why was water collection greater for other samples than others? What was the cause for the increased soil erosion? What do the qualitative observations have to say about the hypothesis? It is captivating to note some discrepancies in the data, which at first could only be attributed to possible errors in the actual experiment. The fact that the potting mix was able to retain the most water out of all three samples without the help of ground cover was astounding. It was expected that the lack of plant roots to absorb water would cause the sample without ground cover (control) to absorb the least amount of water; however, the data shows that this did not happen. The data reveals that the control absorbed more water than the samples of soil with grass, 50 mL and 100 mL more to be exact, based off of how much water was collected. This was later attributed to the fact that the soil with 90% plant cover had a riparian area surrounding the mouth of the bottle where the flow of water exited. In addition, it was later determined that potting soil is created to "absorb water quickly and retain up to two times its own weight in water" (Balcony Container Gardening). Therefore, the potting soil was able to retain the most amount of water even without the presence of ground cover. Despite these observations, the group's hypothesis was not completely invalidated. The water collected from the control sample proved that soil without ground cover is at a greater risk of erosion; it had larger soil particles and somewhat high turbidity. Without plant cover to impede run-off water and facilitate the deposition of sediment, the "soil particles [in the potting soil] can be more easily eroded once they become saturated" (Rudd, P. J). It would certainly aid to prohibit these inconsistencies if all samples of soil used in the experiment had equal water holding capacity. The potting soil used for bottle one (control) and bottle three (90%) proved to be more successful in a sense that it allowed the grass to grow taller and thicker while it was also able to absorb more water than bottle two (10%), which had a much different soil type that could most nearly be compared to mulch. Because of this, the data could most definitely be skewed in some way, shape, or form. Furthermore, while it was evident that ground cover can effectively protect soil from eroding, certain areas of the ecosystem with no ground cover can have major ecological impacts on water quality and soil health. The riparian area demonstrated in sample 3 caused a great amount of soil to erode as the water flowed. Before this area eroded, it was observed that the water quality was much greater than that of the other two samples, and more water was infiltrating through the roots of the grass and into the beaker.
The results of this experiment emphasize the importance of plant cover in preventing soil erosion. This is not an attempt to belittle the role of other types of ground cover. However, the data from this experiment shows that vegetation is the most crucial cover to promote soil health, plant growth, and water condition. After deforestation, planting grass seed would create a long-term solution to various ecological issues. It would reduce soil erosion by obstructing the impact of raindrops on the soil surface, and more importantly by slowing run-off water to give it more time to infiltrate and to allow deposition of deposit. It is also very important to determine the plant type that will be used. Selecting plant species should be done only after considering the climate, soil and grazing regime of a community so that they will persist, and effectively prevent soil erosion. Water filtration ties ties into the ability of run-off to be slowed by the soil's ground cover. Since the sample with grass slows water run-off, it offers the greatest chance of water filtration. In addition, this ground cover creates barriers that allow sediment in the run-off water to be quickly deposited, meaning that valuable plant nutrients are less likely to pollute nearby rivers and streams, and instead can be deposited in the soil to galvanize plant growth.
Overall, this lab demonstrates the importance of maintaining good ground cover over soil. This is further supported by experiments conducted on a bigger scale. For example, Peter Rudd used a rainfall simulator to demonstrate that ground cover effectively protected the soil by "delaying the start of runoff, reducing the rate of runoff was reduced, reducing the amount of runoff, and reducing the amount of silt in the runoff water" (Rudd, P.J). Moreover, the Hubbard Brook Experiment centered on how deforestation affects nutrient cycles in a larger ecosystem. The control group consisted of the loss of water and nutrients form an uncut forest ecosystem, which would be used to compare to the loss in one that was stripped of its trees. V-shaped concrete dams were built across the creeks, and anchored by impervious bedrock, so that all surface water leaving could be measured along with its dissolved nutrient content. The results showed that when deforestation occurred, water runoff increased. "With no plants to help absorb and retain water, the amount of water flowing out of the deforested valley increased by 30-40%" (Landscape Maintenance - Causes of Erosion). Consequently, soil erosion increased, which caused a large increase in the outflow of nutrients from the ecosystem. This demonstrates that deforestation is a disastrous process; it results in a degraded environment with reduced biodiversity and reduced ecological services. The harmful effects of deforestation can only be hindered if efforts are made to ensure that soil has adequate ground cover that will improve its ability to prevent soil erosion.
Citation(s):
"Landscape Maintenance - Causes of Erosion." Causes of Erosion. Landscape Planet, n.d. Web. 02 Nov. 2014. <http://www.landscapeplanet.com/maintenance-1-cause-of-erosion.htm>.
Lang, Des, and McDonald, G. Warren. Maintaining Groundcover to Reduce Erosion and Sustain Production. Tamworth: NSW Department of Primary Industries, 14 Jan. 2005. PDF.
North Carolina Sedimentation Control Law. N.p.: Web. 2 Nov. 2014. NC Department of Environment and Natural Resources, n.d. PDF.
Rudd, P. J. "EFFECT OF GROUND COVER AND REDUCED CULTIVATION ON RUNOFF AND EROSION." The Archives of the Rare Fruit Council of Australia. N.p., Sept. 1987. Web. 02 Nov. 2014. <http://rfcarchives.org.au/Next/CaringForTrees/GroundCoverSoilLoss9-87.htm>.
"Soil Erosion and Degradation." WorldWildlife.org. World Wildlife Fund, n.d. Web. 09 Mar. 2015. <https://www.worldwildlife.org/threats/soil-erosion-and-degradation>.
"What Is Potting Soil?" Balcony Container Gardening. N.p., n.d. Web. 06 Nov. 2014.<http://www.balconycontainergardening.com/gardening/147-what-is-potting-soil>.
By: Noah Nelson