Percolation Test

What We're Doing

In this activity, you will measure and record how long it takes water to soak into the soil at the selected field site. You will use this data to infer the degree of compaction of the soil.

Why We're Doing It

All living things need air and water to survive. Healthy soil has plenty of spaces that allow for the flow of air and water. The Percolation Test measures soil compaction (how packed together the soil is), by measuring the flow of water through the soil. By measuring the compaction of soil, you can learn about the soil's health and how much space is available for living things.

Making the connection:

Getting Our Hands Dirty

Hypothesize

How well does the soil at your field site drain? How compacted is the soil at your field site?

Plan it!

  • If you haven't already done so, choose a field site and map it in your field journal.
  • You also need to decide how many times to repeat the test. Before you begin, think about these questions:
    • How might your results be affected by the number of measurements you make?
    • Will you be more certain that your data are right if you do the test one time or many times?
  • Prepare your can before going into the field:
    • Remove both ends of the can.
    • Use a metric ruler to measure 3 cm from one end of the can, and then draw a line around the perimeter of the can using a permanent marker.
    • If you are working with a group or as a class, be sure to spread out over the field site. When you arrive at the field site, each student or group of students should set up a quadrant in which to work. If you are doing this activity with the Soil Temperature Test, Compaction Test, and the Texture Test, you should do all four activities in the same quadrant.

Do it!

  1. Push the can 3 cm into the soil, until it reaches the line encircling the can.
  2. Pour water into the can until it reaches the top. Once you start pouring, be sure to fill the can quickly. Don't let the water overflow the can.
  3. Immediately use a stopwatch to measure how long it takes for the water to soak completely into the soil. If you do not have a stopwatch, you can use the second hand of a watch.
  4. Repeat this test several times in different spots within your quadrant.

Record it!

  • On the Soil Properties Data worksheet , record how long it takes for the water to soak into the soil for each test you do.
  • Record the average time on your worksheet.
  • If the ground is frozen, write "frozen" on your worksheet.
  • Add the worksheet to your field journal.

Remember, be sci-wise!

  • The safest way to remove the end of a can is to use a can opener. If you are not used to using a can opener, ask an adult to help.
  • Use a water container that will allow you to pour water easily, such as a pitcher or a large water bottle.
  • It is important to pour water into the can as quickly as possible once you start in order to get an accurate time measurement.
  • You'll need to bring enough water to your field site to complete your tests. To be sure you have enough water, pour water into a large container using a can the same size as the can you prepared for the test. Add one can of water for each test you will do.

Thinking About It

  • Did the water soak into the soil quickly or slowly? What does this tell you about the soil compaction at your site? You can read about soil compaction and what it means at the Soil Properties Overview page.
  • Based on the data you collected, do you think your hypothesis was correct or incorrect? Why?
  • How did your data compare with those of other students in other areas of the site?
  • How do your results compare to the Compaction Test results? Would you expect the results of both tests to be the same or different?
  • How might the weather or season affect the data?
  • What other variables might affect the data? How?
  • Now that you have measured the soil compaction at your site, would you expect to find many soil critters there or just a few? What kinds of critters would you expect to see?
  • Based on the soil compaction at your field site, do you think it might be a good place to start a class garden? Why or why not?
  • Looking at the bigger picture, how might the data you collected here help you to answer your research question?
  • Fill in this section of the Soil Properties Overview worksheet .

Still Interested?

If you liked this activity, try this:

  • Brainstorm several things that might affect how quickly water soaks into the soil. For example, the type of soil or how wet the soil is to start with might make a difference. Choose one of these variables and design an experiment to test it. Use the Percolation Test as part of your experiment. What will your hypothesis be? Your controls? How many times will you repeat the test? How will you record your data?
  • Conduct the Percolation Test at three different locations and note the differences. Record the date, weather, and the time of day. Which site had the best drainage? The worst? Why? If you are in an urban area, you can conduct these tests at three different vacant lots. How might human actions have affected the compaction of the soil at the vacant lots? How might this affect plants and animals?
  • Challenge the writer in you by trying to come up with some similes to describe what it would be like to move through the soil when it is highly compacted and when it is not. For example: Moving through highly compacted soil is like _______________. Then, try some analogies. For example: Moving through highly compacted soil is to moving through lightly compacted soil as moving through _______________ is to moving through _______________.

See how many you can come up with!

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Want to find out what's in your soil? Make a Mud Shake! (Just don't try to drink it!)