Compaction Test

What We're Doing

In this activity, you will measure and record how far a pencil can be pushed into the soil at your field site. You will use your 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 Compaction Test is a measure of how packed together the soil particles are and therefore how much space is available for air and water. 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 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 you will repeat the test. As you plan, think about these questions:
    • How might your results be affected by the number of trials (how many times you repeat the test)?
    • Can you be more certain of your results if you do the test many times or just once?
  • Prepare your pencils before you begin. Make sure they have sharpened points, and one pencil should be new or almost new so that it is long enough to be pushed into the ground.
  • 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, Percolation, and Texture tests, you should do all four activities in the same quadrant.

Do it!

  1. Within your quadrant, push the pointy end of a pencil into the soil as far as you can, using normal force.
  2. Use the other pencil to make a mark on the first pencil at the soil level.
  3. Pull the pencil out of the soil. Using a ruler, measure the distance from the mark you made to the pencil point. This will tell you how far you were able to push the pencil into the soil.
  4. Use an eraser to remove the mark you made on the pencil, and then repeat this test several times in different places within your quadrant.

Record it!

  • On the Soil Properties worksheet , record how far your pencil went into the soil each time.
  • If the ground is frozen, write "frozen" on your worksheet.
  • Average the results of all your trials. Record this average on your data sheet.
  • Add the worksheet to your field journal.

Remember, be sci-wise!

  • Push hard enough to move the pencil into the soil, but not hard enough to break it. Do not try to force the pencil into the soil by stepping on it or hammering it. Be especially cautious if the soil may be frozen.
  • Try to use the same amount of force each time you do the test.

Thinking About It

  • What do your data tell you about the compaction of your soil? 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 average soil compaction measurements compare with those of other students and other areas of the field site?
  • Were the results from any of your trials very different from your other results? What might cause that to happen?
  • How do your results compare to the Percolation Test results?
  • How might the weather or season affect the data?
  • What were some other variables that could affect the data? How?
  • Now that you have measured the soil compaction at your site, would you expect to find many soil creatures there or just a few? What kinds of creatures would you expect to see?
  • Based on the soil compaction at your field site, do you think this 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 in this activity 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:

  • Choose several spots around your school or home that have different plant life. For example, choose an area that has a lot of healthy plants and an area that has no plants or has unhealthy ones. Test the soil compaction at each area. How does the soil compaction compare? Can you draw a conclusion about how soil compaction affects plant life just from this test? Why or why not? What other variables besides soil compaction might affect the plant life?

↑ Return to top ↑