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SOIL EROSION
How do different farming practices affect soil erosion
rates?
INTRODUCTION
To properly manage the land, farmers need to
consider what soils have high potential for deg­
radation, the proper vegetation and buffer prac­
tices, tillage and cropping practices, and water
management practices. In this activity you will
study the effects of slope on erosion and simulate
two land management practices that help reduce
erosion.
6% slope: 0.06*24 = 1.44 inches, rounded to
the nearest tenth = 1.4, but a 1.5-inch block is
close enough (6.25% slope).
12% slope: 0.12*24 = 2.88, rounded to the
nearest tenth = 2.9 inches. A 3-inch block
provides a 12.5% slope, which is close
enough.
TOOL KIT
o Two strips of sod, 2 inches wide. One strip
should stretch the width of the pan, and the
other, the length of the pan. Cut from edge of
grassy area.
o Five quart canning jars
o Plenty of water
o Container, minimum 12 inches wide, 24 inches
long, and 1–2 inches deep. Line the container
with plastic to make it watertight.
o Watering can with a sprinkling attachment or
a half-gallon container to sprinkle water
o Catch pan as wide as the container and at least
1 inch deep
o Pen or paper to record findings
o Crop residue from a corn, soybean, or wheat
field. You need enough to cover your pan. (Ask
permission before taking the residue.)
o Stopwatch
o Ruler
D
IT O
o Two of the following soil types in a quantity
that will fill your pan: loamy, sandy, clayey.
The soil should not have any crop residue.
o Masking tape and markers
o Several small blocks to place your container
on three different slopes — 2 percent, 5 per­
cent, and 12 percent. Calculate the heights
you need by multiplying the slope by the
length of the pan, and round to the nearest
one-tenth. For example, for a pan that is 24
inches long:
Use the scientific method to complete this activity.
2% slope: 0.02*24 = 0.48 inches, rounded to
the nearest tenth = 0.5 inch
• Label three quart canning jars: 2% – bare soil;
6% – bare soil; 12% – bare soil.
• Create a table to record your data.
Read
through the steps completely to determine the
data you will be recording.
Part 1
1 PURDUE EXTENSION
• Fill the container with moist soil. If the soil is
dry, add water and mix to make it moist,
almost saturated.
• Prop up the container so the catch pan is
under the open end, and the opposite end is at
a 2-percent slope.
• Sprinkle a half-gallon of water all over the
soil.
• Allow the water to drain for two minutes.
Use the same drainage time for each test so
you have a fair comparison. If there was no
drainage, your soil was too dry; repeat with
moistened soil.
• Pour the water and soil collected into the jar
labeled 2% – bare soil. Make sure you swirl as
you pour to get all the soil.
• Wait until the water stops draining. Then clean
out the catch pan; you don’t need to save this
water.
• Reset your slope to 6 percent, and repeat the
same steps, using a half-gallon of water and
draining for two minutes. Pour into the jar
labeled 6% – bare soil.
• Reset your slope to 12 percent and repeat the
same steps. Pour into jar labeled 12% – bare
soil.
• Compare the quantity of water and soil in
each jar.
Measure the height of the water, and record it
on your data sheet.
Estimate the amount of soil by shaking the
jars, comparing the color, and recording dif­
ferences. Leave each jar overnight so the soil
can settle, then measure the height of the soil
in each jar.
Save the jars for comparisons with other trials
(Part 2 and Part 3).
Part 2
• Level the soil in your container.
• Make a shallow groove from one end of your
container to the other. Cover the groove with
PURDUE EXTENSION 2
a 2-inch sod strip to simulate a grassed
waterway. Place a 2-inch sod strip across the
width of one of the 12-inch ends to simulate a
filter strip.
• Support the container at a 12 percent slope
with the filter strip at the lower end.
• Label a jar 12% – with grass.
• Repeat the steps from Part 1, being sure to
sprinkle the half-gallon of water over the entire
area, both the bare soil and sod strips. Drain
for two minutes. Pour the water and soil into
the jar labeled 12% – with grass.
• Compare the quantity of water and soil in the
jar.
Measure the height of the water, and record it
on your data sheet.
Estimate the amount of soil by shaking the
jar, comparing the color, and recording
differences. Leave the jar overnight so the soil
can settle, then measure the height of the soil
in the jar.
• Save the jar for comparisons with other trials
(Part 1 and Part 3).
Part 3
• Remove the sod strips and level the soil. Mix
your crop residue over the entire surface, mix­
ing it with the top of the soil.
• Support the container at a 12 percent slope.
• Label a jar 12% slope – crop residue.
• Repeat the steps from Part 1, being sure to
sprinkle the half-gallon of water over the
entire area. Drain for two minutes. Pour the
water and soil into the jar labeled 12% – with
crop residue.
• Compare the quantity of water and soil in the
jar.
Measure the height of the water, and record it
on your data sheet.
Estimate the amount of soil by shaking the
jar, comparing the color, and recording
differences. Leave the jar overnight so the soil
can settle, then measure the height of the soil.
• Save the jar for comparisons with the other
trials (Parts 1 and 2).
• Compare Your Data
Compare the data that you recorded for all five
jars.
DIG DEEPER
• Use the instructions at the NRCS Web Soil
Survey, ( – WSS Instructions.pdf), to
find information about soils at your home
or nearby that might erode easily.
Repeat all three parts of the process with the
second soil type.
LIFE SKILLS
THE SCIENTIFIC METHOD
• Evaluating data
• Keeping records
ch
at
• Using scientific methods
Share What Happened : What affected the
amount of soil erosion the most, changing the
slope or changing the soil cover?
1. Define the problem. (Write a sentence or two.)
2. Develop your hypothesis. (What do you think
can be done, and how will it help?)
3. Conduct experiments to prove or disprove
your hypothesis and record your data.
4. Compare the data that you have collected.
5. Draw conclusions: What did this experiment
show?
Apply: What practices can farmers use to reduce
erosion and water runoff?
Generalize to Your Life :
• Why is it important to minimize soil erosion
and water runoff?
• What effect does conserving soil and water
have on the environment and your community?
3 PURDUE EXTENSION