Activity: Test water infiltration and retention properties of soil using a model soil column
Level: College students (can be easily simplified for earlier levels)
Time: Approximately 50 minutes, depending on time needed to present results
Subjects: Ecology, environmental science, general biology, agriculture, earth science
After successfully completing this activity, the student will be able to:
Author: Rebecca Burton, feel free to email questions and comments from you and your students. Creation and maintenance of this web site was made possible by NSF-ILI Grant DUE 9750658.
You may want to give students some general information on what soil is, how it is formed, and what a soil profile is. A brief explanation of leaching of nutrients will help students understand that water filtration properties are important for nutrient dynamics as well.
Ask students as a class to propose variables that might affect how deeply water will infiltrate into soil, how quickly water will percolate through a column of soil, and what influences erosion. Some factors involved might include size of particles in substrate, amount of water, rate of water delivery, density of soil, whether soil is already wet, water temperature, amount of organic material in soil, or water channels in soil (artificial or caused by animal or plant activity).
Have each pair of students decide on a hypothesis to test. Remind them that it must be a falsifiable statement.
Ask the students to identify the independent variable they will be manipulating and the dependent variable they will be measuring.
Have students design a test using a model soil column they create in their graduated cylinders. Remind them to keep all independent variables the same, except for the one they are testing. If time allows, they might be able to test for a correlation, such as amount of water added vs. depth of water penetration.
Once students have finished their experiments and evaluated their hypothesis using their data, have them make a brief presentation of their findings, if time allows. They can usually do their presentations in just a few minutes.
In future class periods, you might wish to discuss any of the following topics:
The following is a student worksheet that you can cut and paste for own classroom use. Please include the source information if you duplicate this lab or any part of it.
What is the independent variable you will be manipulating?
What is the dependent variable you will be measuring?
Plan an experiment to test your hypothesis using a model soil profile in your graduated cylinder. Remember to keep all of the independent variables constant except for one.
Make your own soil column in a graduated cylinder. Record the levels of different substrate layers so that you can replicate your column.
Pour in a measured amount of water. Wait for the water to percolate down the column. Record the appropriate data (such as how far the water percolates down, how long it takes, etc.). Keep good notes in your lab notebook and be prepared to report back to the class.
If this were the usual amount of precipitation, where would the nutrients end up?
Was your hypothesis refuted or supported by the data?
When you are finished, empty your cylinder into the waste soil container. Wash your glassware. Clean up your workspace.
Make a brief presentation of your findings.