Environmental Science
Soil Salinization Lab
Background: Soil salinization is a serious threat to agriculture. Excessive salinity costs
the United States billions of dollars each year. As new land comes into use, it is often in
arid areas, which are highly susceptible to the problems associated with soil salinization.
Irrigation water contains a variety of dissolved salts including NaCl (sodium chloride),
MgCl2(Magnesium chloride), CaCl2(Calcium chloride), Na2SO4 (Sodium sulfate), CaSO4
(calcium sulfate), MgSO4(magnesium sulfate), Na2CO3 (Sodium carbonate), CaCO3 (calcium
carbonate), and MgCO3 (magnesium carbonate) among others. When a field is irrigated,
much of the water can evaporate, leaving these salts behind as a thin layer on top of the
soil. If you take a glass of tap water and leave it in the sun until all the water evaporates, a
film will be left on the glass. These are salts. Over time, salts build up on fields until the soil
is so salty (salinized) that seeds will no longer germinate in the soil.
Throughout this lab, your group will work collaboratively and use the scientific method
to answer questions about the soil salinization problem. Your group will determine the salt
concentration at which a plant species will show the initial effects of salinization, as well
as the salt concentration at which the plant species will no longer germinate. To complete
the analysis, your group should determine the highest salt concentration at which all of
the seeds of the plant species will germinate, the lowest salt concentration at which none
of the seeds of the plant species will germinate, and as much data about the intervening
concentrations as possible.
Goal: Your goal for this experiment is to design a set up in which you can test varying levels
of salinity in soil and how they effect plant growth.
You will: Research and write down known information, develop a testable hypothesis by
inferring and creating a prediction, designing and carrying out an experiment, collecting
and analyzing data, and finally writing a conclusion.
**To help fuel your thinking, answer the following questions about soil, salinization and
plant growth.
Environmental Science
1.)
What is the process of salinization?
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2.)
How does salt build up in soil?
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3.)
Where in the world is this occurring?
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4.)
How does salt affect plants?
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Brainstorm:
Write down an experimental design you could use to test the amount of salt in soil that A.
would not affect plant growth, B. Would limit plant growth but not prevent it, and C. Would
prevent germination altogether (be sure to write in complete sentences. All you are doing
here is giving a brief description of how would set up and test this idea)
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Discuss: Now that you have your idea for an experimental design, discuss with another
group how they want to test soil salinization’s effect on plant growth. Are there any
improvements or changes you would like to make to your design now?
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Environmental Science
HOW will you measure the affect of salt on plant growth?
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What will your INDEPENDENT VARIABLE in this experiment be? (Remember, the
independent variable is that variable you have control over. It is the variable you decide to
change)
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What will your DEPENDENT VARIABLE in this experiment be? (Remember, the dependent
variable is the variable that will change because of the independent variable. It is the
variable you will be measuring)
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What are some outside variables (beside salt) that you need to make sure is consistent for
each plant so we don’t interfere with the growing process in any other way?
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As a class: Now that we have discussed as a class what the best means for an experimental
design will be, what materials will you need for this experiment? (Try to be specific)
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