Soil erosion by water and wind
Course: ES 110L Introduction to Environmental Science Lab
Unit: Soil
Content: Soil erosion
Lab #7: Soil Erosion and its effect on Natural Resources
Degradation Processes in Soil Environments
TA:
Date:
Goals
The goal of this lab is to understand the natural and
anthropogenic factors that cause the loss of soil, one of
our most important natural resources, through
degradation processes such as soil erosion and to
identify some ways to prevent or decrease it.
Introduction
Coastal erosion at Happisburgh, Norfolk, England.
Image Credit: Wikipedia. http://www.wikipedia.org
Soil can be defined from several points of view.
According to professors Kohnke and Franzmeier in their
book Soil Science Simplified, the definition of soil for an
agronomist is “the unconsolidated cover of the earth,
made up of mineral and organic components, water and air and capable of supporting plant
growth.” This definition includes one important function of the soil which is to grow plants,
probably one of the most important from our point of view as human beings. Certainly, our
survival depends on our capacity to produce enough crops to feed the increasing population on
the earth. And to do that, we need to maintain “the body and the fertility of the soil,” as Dr.
Kohnke and Dr. Franzmeier state in their book.
However, there are many problems affecting the soil. One of the most important is soil erosion
which “is the process of detaching and removing soil materials from their original sites” (Kohnke
and Franzmeier, 1995, p.113). Erosion is caused mostly by natural factors such as flood water,
wind, and volcano eruptions among others. But soil erosion can also be caused, or at least
increased, by human activities such as deforestation, overgrazing, and road or trail building.
While some amount of erosion is natural and, in fact, healthy for the dynamic process of life on
earth, too much erosion can reduce soil fertility, pollute water bodies and create other problems.
In this lab we are going to explore, through three different experiences, some factors contributing
to soil erosion and how erosion can be prevented or decreased.
Environmental Science Laboratory 110L
New Mexico State University, Department of Agronomy and Horticulture
1
Soil erosion by water and wind
Course: ES 110L Introduction to Environmental Science Lab
Unit: Soil
Content: Soil erosion
Pre-lab Questions and Resources
•
According to the soil taxonomy that distinguishes twelve soil orders, identify what soil order
is the most likely to be found in the state of New Mexico. (Remember New Mexico is a big
state with lots of different ecosystems). Also, name two soil orders that you would probably
not find in New Mexico.
The Twelve Soil Orders. Soil Taxonomy. University of Idaho, College of Agricultural and Life
Sciences http://soils.ag.uidaho.edu/soilorders/index.htm
•
In the website “Soil Erosion Site” (see link below) you will find a section entitled “About Soil
Erosion.” There, click on the link “What is soil erosion?” and read the information to answer
the following: Is soil erosion a natural process, a human induced process, or both? Give two
or three examples to support your answer.
Soil Erosion Site. Website created and maintained by nearly 50 soil erosion scientist from 16
countries
http://soilerosion.net/
•
Following the link below you will find some fun cartoons related to erosion. Observe the
cartoons 3 and 4 and explain briefly why they represent an unwelcome example of erosion.
Refer to some real examples taken from the news regarding this phenomenon.
Erosion Cartoons. CSL Cartoon Stock
http://www.cartoonstock.com/directory/e/erosion.asp
Key Words
Soil, soil taxonomy, erosion, runoff water, slope, surface cover, detachment, transport
Objectives
1. Understand the definition of soil, erosion, runoff water, detachment, and transport.
2. Observe and identify some factors causing soil erosion.
3. Compare different samples of soil to determine how they are affected by water and wind as
erosion agents.
4. Be aware of the importance of soil for life on Earth and the role of human beings in its
preservation.
Environmental Science Laboratory 110L
New Mexico State University, Department of Agronomy and Horticulture
2
Soil erosion by water and wind
Course: ES 110L Introduction to Environmental Science Lab
Unit: Soil
Content: Soil erosion
Procedure
Materials
Boxes
Different soils (clay, sand, organic-rich)
Fan
Water
Protractor and/or wedges of known slope
Ruler
Fork
Toothpicks
Hay straw
Plastic bags
First activity: Observing drops of water falling on soil
1. Take each kind of soil provided (compost-amended garden soil, sandy desert soil, clay soil)
and label them A, B, and C respectively.
2. Put a sample of each soil in a different box.
3. Go to the sink area and set the faucet so it leaks at a rate of approximately one drop per second.
4. Place each sample of soil under the leak for 1 minute and carefully observe the effect of the
drops on the soil.
5. Determine the erosion caused by the water in a scale from 0 to 5, where 0 means no erosion
and 5 means high level of erosion with deep and visible marks on the soil. Please, give a
description of the other intermediate levels.
6. Clean each box and refill it with a new sample putting a cover of hay straw over each one.
7. Repeat the procedure described in (4) and (5) and compare the results for each kind of soil (see
Calculations and Data Presentation, and Questions sections).
Second activity: Simulating runoff water with different slopes
8. Put a sample of sandy desert soil (B) into a box compacting it as much as you can.
9. Set the slope of the box at 5%. The slope (S) is calculated by:
S = ( h / l ) * 100
Environmental Science Laboratory 110L
New Mexico State University, Department of Agronomy and Horticulture
3
Course: ES 110L Introduction to Environmental Science Lab
Unit: Soil
Content: Soil erosion
Soil erosion by water and wind
10. Simulate runoff water by splashing 500 ml of water on the highest point of the box.
11. Determine the impact of the runoff water over the soil using a scale from 0 to 10, where 0
means “no impact” and 10 means “a high impact with a large amount of soil displaced leaving a
deep and visible mark”.
12. Repeat procedures described in (10) and (11) using the following slopes: 25%, 50%, and
70%. Do not forget to record your results (see Calculations and Data Presentation section).
Third activity: Observing the effect of the wind on soil under different conditions
13. Fill the box with dry soil assigned to your group compacting it as much as you can.
14. Set the box inside the plastic bag as is shown in the figure.
15. Apply wind over the soil during 1 minute observing carefully what happens on the surface.
16. Establish, using a scale from 0 to 10, the wind’s effect on soil erosion.
17. With the same sample and using a fork “plow” the surface of the soil and repeat the procedure
described in (14), (15), and (16).
Environmental Science Laboratory 110L
New Mexico State University, Department of Agronomy and Horticulture
4
Soil erosion by water and wind
Course: ES 110L Introduction to Environmental Science Lab
Unit: Soil
Content: Soil erosion
18. Now, put toothpicks on the soil covering the whole surface, as is shown in the figure, and
repeat the procedure described in (14), (15), and (16).
19. Finally, take out the toothpicks and wet the soil taking care not to over-wet it. Then, repeat
the procedure described in (14), (15), and (16).
20. Share the results with the other groups and take note of their results, consolidating all results
in one table.
Calculations and Data Presentation
Soil Sample
A
Erosion Level
Covered
Uncovered
B
C
Slope
Erosion Level
5%
25%
50%
70%
Environmental Science Laboratory 110L
New Mexico State University, Department of Agronomy and Horticulture
5
Soil erosion by water and wind
Course: ES 110L Introduction to Environmental Science Lab
Unit: Soil
Content: Soil erosion
Treatment
Soil A
Wind erosion effect
Soil B
Soil C
Dry, and uncovered
soil
Dry, uncovered, and
plowed soil
Dry, covered, and
plowed soil
Moist, and
uncovered soil
Questions
1. What is the effect of soil covers in preventing soil erosion by water?
2. Based on your observations comment briefly on the custom of burning crop residues after
harvesting the crop.
3. How does slope affect erosion by runoff water?
4. Based on your data, what would you recommend to someone who wants to cultivate on a hill
with a slope of 60%?
5. In which soil is the effect of wind erosion stronger? How can this erosion be prevented?
6. Based on your results, what would be your advice to the Las Cruces City Council in terms of
wind erosion with respect to the new urbanization areas near the Organ Mountains? Use your data
to support your advice.
Important information
Do not forget to submit the “Full lab” report by 5 p.m. on DATE to TA: TA email
Environmental Science Laboratory 110L
New Mexico State University, Department of Agronomy and Horticulture
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