Soil Temperatures:
Planning Your Own Investigations

As scientists observe the natural world, they ask questions about things that interest, surprise, or confuse them. Then they set up investigations to try to answer their questions. As scientists participating in Journey North's Tulip Experiment, you will surely wonder about many things — and have a chance to explore them firsthand. Let's consider soil temperatures.

Start with Questions
You know a bit about soil. You've probably played in it. You certainly dug into it when you planted your tulips. You may even be keeping track of soil temperatures.

  1. What kinds of things do you wonder about soil temperatures? Here are some of the things other Journey North students have wondered:
    • Will the underground temperature change during a 24-hour period?
    • Is the soil temperature higher or lower than air temperature?
    • Is it cold deeper in the ground?
    • Why does the soil still feel so cold?
    • Does sunshine change the soil temperature underground?
    • Do soil temperatures affect how fast tulips grow?
    • How hot or cold is it a mile down? In the center of the earth?
    • Are soil temperatures the same in different microclimates?
    • Are soil temperatures of bare ground and insulated ground different? Does the amount of insulation matter?

  2. Look at these questions (and your own). Put an E by questions you can answer through observations or doing an experiment. Put an L by those you'd have to answer by doing library research or talking to an expert. Do the same with your own list.

    Asking a good question takes some thought
  3. Ask a "testable" question. Choose one of your questions to explore. You may need to revise it so it's not too broad or vague, and so it identifies the factor(s) you'll investigate. Here's an example:
    You wonder: Is it cold deeper in the ground?
    Testable version:
    How do soil temperatures change with increasing soil depth?

Plan Your Investigation
Teachers: Try a Hobo Data Logger.
Students can use it to measure and graph soil temperatures, moisture, and more!
As you plan to carry out your investigation this spring, try to answer these questions in your science journal:
  • What are we trying to find out?
  • What do we already know or think you know?
  • What's the best way to answer our question?
  • What variables/factors should we consider (e.g., soil temperature and depth)?
  • How will we keep it "fair"? (That is, keep everything the same except the variable we're testing. In this case, soil depth.)
  • What kind of data (e.g., observations or measurements) will we collect?
  • What do we predict we'll find (or What's our hypothesis)?
  • What evidence would support our predictions/hypothesis?
  • How will we organize our data so we can make sense of it?

Dig In!

National Science Education Standards

  • Ask a question about objects, organisms, events.
  • Identify questions that can be answered through scientific investigations.
  • Science investigations involve asking and answering a question and comparing that to what scientists already know about the world.