Dirty Day Experiments
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Dirty Day: Observing and Questioning

This soil collection activity will let you compare soil samples from your school with samples from other schools. You will begin by collecting soils from your garden and two other sites at your school and finding out what is in them.

Investigation

Here are the things to consider while you do the following activities. When you are finished, you should be able to answer these questions.

  1. What is in our garden soil?
  2. Is our garden soil the same as other soil around our school?
  3. How do our soils compare with the soils from other schools?

Methods

  1. Collect soils from three locations at your school. Be sure to draw a map, or write a good description, to show where you collected your three soil samples. Get your soil from:
    • Your garden
    • Near a parking lot or driveway
    • You choose a third place.
  2. At each location that you have selected, do the following:
    1. dig a hole that is approximately 6 inches wide, 9 inches long and 4 inches deep;
    2. put all the soil from the hole into a bucket (or something);
    3. mix the soil in the bucket well;
    4. take three cups of soil from the bucket and put it into a plastic bag;
    5. label the bag so you know what location the soil came from;
    6. put the rest of the soil back into the hole.
    7. Repeat this for your other two locations. You will have a total of three plastic bags of soil with three cups of soil in each bag.

Procedures

Do these activities for each soil sample.

  1. Remove one cup of soil.
  2. Find the weight of this one cup of soil.
  3. Describe the soil sample (color, texture, stuff that is in it, etc.).

Soil Content

  1. Sift the soil through a wide screen (1/2 inch mesh). Shake the screen back and forth. DO NOT smash the soil with your hands.
  2. Find the weight of the soil that went through the screen.
  3. Describe the soil that went through the screen (color, texture, smell, etc.)
  4. Identify the stuff that did not go through the screen (rocks, clods of soil, leaves, etc.).
  5. Screen the soil that went through the first screen a second time using the small screen (1/8 inch mesh).
  6. Find the weight of the soil that went through the second screen.
  7. Describe the soil that went through the second screen (color, texture, smell, etc.)
  8. Identify the stuff that did not go through the screen (rocks, clods of soil, leaves, etc.).
  9. Summarize your data so that you can share it with the other schools.
    1. Describe how your three soils are the same, how are they different?
    2. How much of your sample was stuff that was not soil? What percentage?
    3. What stuff was in your soil?
    4. Predict whether you think your soils will be the same or different than the soils at the other schools.
  10. The above exploration could also include separating soil using water. To do this:
    1. Take 1/2 to 1 cup of soil and place it in a quart jar;
    2. add water until it is 1 cm above the soil;
    3. place the lid on the jar and shake like crazy;
    4. let it set and look at the layers that are formed;
    5. you may want to examine the time it takes for layers to form, if they change over time;
    6. describe the layers; draw pictures, measure heights, graph, calculate ratios.
  11. Describe the condition of the soil you collected. (frozen, covered with snow, wet, dry, etc.)
  12. Explain how the soil would be different if frozen or covered with snow.
  13. What do you think soil that came from near a river would be like? Describe how it would be different from your soil or how it would be like your soil.

Water Content

How much water is in your soil? NOTE: You will need to have a sensitive scale to perform this experiment.

  1. Take 1 cup of ORIGINAL soil (from the plastic storage bag) and weigh it.
    1. Spread the soil out on paper towel and put in a warm, dry place for 7 days.
    2. After 7 days weigh the soil again (dry weight).
    3. Spread it back out again for 3 more days.
    4. Weigh the soil again. The weight should be the same as on day 7. If it is not, let it dry longer until the weight is constant.
    5. Subtract the dry weight from the original weight and you will have the amount of water that was in your sample.
  2. Is the amount of water in your samples the same for each location?
  3. Can you explain differences in the amount of water in your soil samples using the information you found out about what was in your soil?
  4. Can you predict whether a sandy soil or clay soil would hold more water?

Seed Content

What seeds are in your soils? To answer this try the following:

  1. Take 1 cup of your ORIGINAL soil (from the storage bag).
  2. Put the soil into some sort of container that has a clear cover. (The take-out containers from salad bars or that some sandwiches come in work very well. Otherwise, use a plastic pot (~4" diameter) and put a "Tent" over it using saran wrap or plastic. Seal it around the pot using tape.)
  3. Before sealing your container, water the soil.
  4. Put your "greenhouse" in a window so it will get good light.
  5. Record the number of plants that grow every day for two weeks.
  6. On the day that you can see a seedling and count it, pull it out. (This makes it a lot easier to keep a seed germination count).
  7. Put the seedlings in your science notebook, make drawings of them or take pictures of them as a record of what germinated. Later you might want to try and figure out what they are.
  8. Summarize your data: Total number of seedlings, graph the number for each day, graph the cumulative number, how many different seedlings germinated, how many of each type of seedling germinated, how many were weeds, etc.

Group Discussion

  1. Describe the soils that produced seedlings, including what was alike and what was different.
  2. Where do you think the seeds that were in your soil came from?
  3. If no seedlings germinated, why do think there weren't any?
  4. What kinds of seeds do you think students at the other schools will find?
  5. How would this change if you took your soil sample from only the top two inches of soil? What about if the sample was from 8 inches deep?

Sharing your data

Keep accurate records and share them with the other schools using email or letters. Do some graphing and illustrations that can be displayed on walls or in magazines.

This activity created by Norm Lownds.