Part 1
Question: Do plants reduce the effects of soil erosion?
Independent variable: Soil (one pot/bread pan has NO seeds in the soil and the other pot/bread pan HAS seeds)
Dependent variable: weighing the amount of soil that falls off after our “rainfall”
Plan/goal: to compare the erodibility of soil when there is a plant growing from it vs when there isn’t. We will then be able to test the theory that plants and their roots stop erosion.
Prediction: After doing some research, we predict that our experiment will work. Multiple sources state that the roots of a plant usually help keep the soil together. We also imagine the leaves blocking away the sun, keeping the soil moist, more compacted, and less likely to move. This gives us even more reason to believe that our experiment will work.
However, because we may not have enough time to let the plant grow to full size, there is a chance that the seeds won’t develop strong enough roots to hold the soil together. The leaves would also be a too small and unable to block away the sun, if there is ever a need to. The water would evaporate, leaving the soil dry and erodible. Another problem we might face is erosion caused by fragile roots: we will be using the seed of a small plant (instead of a tree, for example), so they will most likely be thin and weak. This is another prediction as to why it might not work.
Part 2
Materials:
- 2 Aluminium bread pans
- 2 Aluminium cake pans
- Soil/seedling mix
- 1 small bag of radish seeds
- Labels
- Permanent marker
- Scissors (we used tweezers)
- Full-size watering can
- Sunny windowsill
- Short plastic container (or any other object to prompt up the bread pan)
- Bathroom test area
- Kitchen scale
- Lab notebook
Safety risks: Possible stabbing by scissors when poking holes into bread pan
Ethical, cultural and/or environmental issues in performing the experiment: soil erosion (when topsoil is moved from one spot to another) would be the environmental issue, as its effects go beyond the loss of fertile land. It has led to increased pollution and sedimentation in streams and rivers, clogging waterways and causing declines in fish and other species. Degraded lands are also less able to hold onto water, which can worsen flooding.
Although soil erosion is a serious problem for us and many other species, it cannot have any impact on the environment during our experiment. Besides the fact that we will be using plants to test our theory, we won’t really be putting any environmental aspects at risk.
Step-by-step instructions:
- Gather the materials listed above.
- Weigh your empty cake pan for later and record the data into a notebook
- Fill the 2 bread pans with about 3 1/4 cups of soil each (6 1/2 in total)
- Plant the radishes about 1/4 inch deep and 1/3 inch away from each other. There should be room for at least 12
- Place labels on the bread pans, making it clear which bread pan has seeds and which one doesn’t
- Use scissors to poke holes into the bottom of the bread pan to let the excess water out
- Place the bread pans in a cake pan (the bread pans with seeds go into one cake pan and the bread pans without seeds into a different cake pan)
- Water the bread pans with 1/2 cup of water in a rain falling motion
- Place both cake pans (with bread pans inside of them) on a sunny windowsill/growing room/greenroom
- Let the plants grow for 7 days watering each bread pan everyday (1 cup of water in a rain falling motion)
- Make sure you are recording all of your data throughout the experiment
- Water every day 1/2 cup of water in a rain falling motion
Testing the soil on the 7th day of letting them grow:
- Make 2 vertical cuts down the short side of the bread pans, and fold it down
- Empty and dry out the cake pans
- Place the uncut bread pan side on a container and the cut side in the cake pan. Make sure all this simulates as a hill
- After the bread pan is simulating a hill, water the “hill” in a rain falling action
- Carefully lift the bread pan up and remove the water, leaving just the soil in the bread pan (this is the soil from the erosion)
- Place the cake pan (with the soil) onto a scale and subtract the initial cake pan weight
- Repeat all these steps with the other bread pan
- Compare and analyze your findings
Part 3
Planting the seeds:
Testing the soil on the 7th day of letting them grow:
Part 4
a. Did your findings support your hypothesis (prediction)?
Because our prediction was two-sided, we were both correct and incorrect. We worried that we wouldn’t have enough time to let the plant grow to full size/develop strong enough roots to hold the soil together. That wasn’t a problem for us, as we still conducted a successful experiment. However, we believe that if our roots had grown a little more, even less soil would have been eroded. We confirm our hypothesis that roots help keep the soil from eroding, but do not think the leaves had a significant impact on the growth of the plant.
b. Analyze the cause-and-effect relationship you witnessed. Is this consistent with other scientific findings? You will likely need to do some research here.
Our experiment results were indeed consistent with other scientific findings: there was 20 g more soil eroded from the pan without seeds, confirming that plants stop soil erosion.
d. Evaluate the methods you used and the conditions of the experiment.
• What were the sources of error or uncertainty? We were not sure if we’d have enough time for the plants to grow to full size, and we were right: if we had planted them any later, our experiment wouldn’t have worked.
• How can your experiment be improved? We could have counted while pouring the water, as we believe it had an influence on the amount of soil eroded. Our watering can was not ideal, therefore leaving it extremely hard to be precise. We tried our best.
e. What implications do your findings have?
Our findings show that if plants can lessen the effects of soil erosion, we should be planting more of them. We could benefit the world by solving some serious environmental issues, like the abundance of carbon dioxide in the atmosphere.