Soil Erosion Lab
Collaborators: Sarah Pippin, Anna Swenson, Caroline Corrigan, and Amanda Goodale
Introduction and Problem
The goal of this Soil Erosion lab is to evaluate how the type of soil covering
affects the amount of soil erosion. This topic is highly invaluable in being able to
determine which types of soil coverings prevent or increase the amount of soil erosion.
Firstly, soil is whatever unconsolidated material is found on the surface that contains
living matter, minerals, air, and water ("Soil Layers"). It is formed through physical and
chemical weathering of rocks on the surface of the Earth. Soil can be classified through
its color, texture, structure, and mineral content. In specifically agriculture, soil erosion
is a natural process by which natural forces such as wind and water or forces related to
farming such as tillage wear down a field’s topsoil layer (Ritter). In this lab, we
specifically tested the amount of water erosion that occurred. Erosion has many negative
effects on the environment. First, erosion can affect the soil quality: erosion mainly
impacts the topsoil, which contains most of the nutrients and organic materials needed for
efficient plant growth. It also affects water quality, as the water that causes erosion can
run off into surface waters carrying soil particles and agricultural chemicals, which
pollute the water. Erosion can also negatively affect air quality and can pollute the air
with chemicals from the floating soil particles. Drastic soil erosion may also have an
impact on the economy, as demonstrated in the Dust Bowl of 1930 (Wakefield).
Specifically water erosion can create an on-site loss of agricultural potential and can also
have an off-site effect on downstream movement of sediment, causing flooding and
silting up of reservoirs. Since soil is formed at a rate of only about 1 centimeter per every
100 to 400 years and is considered a nonrenewable resource, it is important that humans
do our part to try to reduce the amount of erosion that often happens frequently due to
human activity ("Soil Erosion"). Prevention measures can include the use of contour
ploughing and windbreaks, strip cropping, making sure plants are always growing on the
soil, and using a crop rotation system.
Hypothesis
In this lab, we tested the amount of soil erosion that occurs when soil is
covered by grass, pine straw, and leaf litter. I predict that if we test the effects of water
erosion of these three coverings, the grass sample will erode the least because the grass’s
roots will strengthen the soil.
Parts of the Experiment
Control group- the soil only bottle
Experimental group- the other three bottles of grass, pine straw, and leaf litter
Independent variable- amount of water poured into bottles
Dependent variable- amount of erosion
Controlled variables- amount of water, degree of tilt, and amount of soil
Materials and Methods
The materials used in this experiment were the NPP lab bottle containing planted
grass, four 2 liter bottles cut in half, 8 200 mL beakers, potting soil, water, leaf litter, and
pine straw litter. We also used paper and a pencil to record our information. First we cut
two new bottles into a boat form with an opening at the top and filled both with a base of
potting soil. We filled one bottle with leaf litter and one with pine straw. The bottles
were placed on top of a container, their caps were opened, and they were tilted at an
angle with the bottom of the bottle at 4 ½ inches above the container. We placed three
beakers under the spout of each bottle to catch the water run-off. Then we filled the other
three beakers with 200 mL of water and set a timer for 2 minutes. Each beaker with 200
mL of water was poured in the separate bottles at the same time, and we let the water run
off until the timer buzzed. The comparison of the amount of water, amount of soil, and
coloration of the water between the three samples were observed and recorded.
Additionally, at home I performed the same procedures with a bottle filled with only
potting soil to serve as my control group that I could compare to the other bottles. I
recorded all of the data in the data table and proceeded to analyze my observations.
(Leaf litter and pine straw)
(Cut the bottles)
Data and Data Analysis
(Container with beakers under bottles to catch runoff)
(Lab with soil-only bottle performed at home)
Data
Water
Captured
Bottle
Grass and soil
Pine straw
and soil
Leaf litter and
soil
100 ml
Soil
200 ml
100 ml
50 ml
Observations
Bright yellow with bits of
soil
Murky color with a little bit
of soil
Murky color with a speck
of soil
Dark brown color with a
muddy texture
Constants:
Water input- 200 ml
Time for water to stop collecting- 2 minutes
Tilt of bottle- 4 ½ inches
(Pine straw, Leaf litter, Grass)
(Soil only)
Analysis
In this lab, we tested the amount erosion that occurred on bare soil, soil covered
with pine straw, soil covered with leaf litter, and grass. The bare soil experienced a lot of
erosion, as the water that ran out of the bottle was a muddy mixture containing a lot of
soil and water. The most water was collected from this sample, at 200 ml after 2 minutes
of draining. The erosion that occurred for the soil covered in pine straw created a 100 ml
accumulation of water with a few specks of soil in it after 2 minutes. The soil covered in
leaf litter only created 50 ml of drainage with very barely any soil content. Both the pine
straw and the leaf litter created a murky colored water runoff, likely attributed to the
specks and particles collected from the water passing over the substances. The grass
created an erosion of 100 ml of water with a good amount of soil in it, however the runoff
water from this sample was much clearer than the other three samples. The grass, leaf
litter, and pine straw all created much less erosion than the soil-only bottle did, showing
that any substance covering the topsoil will serve to somewhat decrease the amount of
soil erosion.
Conclusions
At the beginning of this lab, I hypothesized that if we tested the effects of water
erosion of these three coverings, the grass sample would erode the least because the
grass’s roots will hold the soil in place. After performing the lab, I discovered that my
hypothesis was inaccurate in regards to the results of the experiment. We found through
this experiment that the leaf litter actually created the least amount of runoff of both
water and soil, and the grass created the most. However, through further research after
the lab was performed, we found that our results were inaccurate, and in fact the grass
should have created the least amount of erosion. The inaccurate results of this
experiment could have been due to over packing the bottles with too much leaf litter and
pine straw so that the water could not reach the soil.
In nature, these substances of pine straw and leaf litter will usually be more
scattered and dispersed over the ground so that the water can seep through them to the
soil. Then, the soil covered by these substances will usually cause more erosion since
there is nothing holding the soil together. Grass, however, contributes its roots to making
the soil stronger and less susceptible to erosion and runoff. Many officials encourage
planting more crops and plants, as plant cover significantly helps reduce erosion. Plants,
including grass, slow the water runoff, hold the soil in place, and break the impact of rain
("Importance of Plants in Preventing Soil Erosion"). Taking measures to limit erosion
would be in the best interests of nature and human beings. Soil impacts so many
processes and aspects in life: it is a major part of the ecosystem and contributes greatly to
the water cycle ("Erosion and Soil Quality: Prevent Erosion"). By using the land wisely,
humans can greatly limit our effect on the environment and soil erosion.
Works Cited
"Erosion and Soil Quality: Prevent Erosion." Science of Life Explorations (n.d.): n. pag.
Integrated Pest Management Program. Cornell University. Web. 7 Nov. 2014.
"Importance of Plants in Preventing Soil Erosion." Ecomerge. N.p., 3 June 2010. Web. 07
Nov. 2014.
Ritter, Jim. "Soil Erosion- Causes and Effects." Ontario. Queen's Printer for Ontario, Oct.
2012. Web. 05 Nov. 2014.
"Soil Erosion." Landcare South Africa. N.p., 1999. Web. 06 Nov. 2014.
"Soil Layers." Soil - EnchantedLearning.com. EnchantedLearning.com, n.d. Web. 07
Nov. 2014.
Wakefield, Petra. "Harmful Effects of Soil Erosion." EHow. Demand Media, 15 June
2011. Web. 07 Nov. 2014.