The Dirt on Soil

This week we had a great time playing with dirt! Scientifically we like to call it soil, not dirt, and the young scientists used their inquisitive minds to examine what exactly is in soil and it comes from. We learned that soil and rocks are similar, expect that rocks go under pressure and heat. Students also learned about the ecological, biological and topological factors that contribute to soil formation over hundreds and thousands of years. For example, many of us know that rocks will eventually erode into tiny pieces that become soil. But others of us might not appreciate the role that microorganisms play in soil formation (they help break down organic material such as leaves and other dead bugs) or that soil contains large amounts of air and water. 

We looked at the 3 different types of soils (sand, silt, and clay) and focused on the texture and color. Students collectively described their observations to each other. These three types of soils, along with organic matter, combine to create soil we find in nature. 

Experimentally, students examined clay, sand, topsoil, and sphagnum moss (an additive to soil). They noticed differences in the soil colors and were able to correlate that color to what is in the soil itself. We tried to see which soils had more of sand, silt, clay, and humus. Dark brown/black soils tend to contain lots of broken down organic material, sandy soils tend to contain many mineral fragments and even parts of shells, and red toned soils might contain high amounts of iron. We learned that the soil needs to have access to oxygen, in order for the iron to “rust” and turn this red-ish color. Students also observed the texture of the soils noting that some soils contain smaller particles than others. Finally, students observed how well soils can hold, or not hold, water. We learned that clay holds onto water the most, but also takes the longest time to absorb. Moss absorbed the most water (from everything we tested), which is why it’s a great additive to soil. Sand held onto water the least, which is also why it is difficult to grow plants (though some plants love this type of soil!). All of these factors (color, texture, water handling ability) are important in determining how healthy a soil might be for growing crops or how productive soil might be in filtering out impurities from water.

Feel free to look more closely at the soil in your own yard now and see what you can find!

13 Comments:

  • avatar
    Jenny / Reply

    it was really fun when we got to poor water into different types of soil and weighed them

  • avatar
    Kerri / Reply

    I had so much fun seeing what would happen when we poured water into the different soils. And see which one weighed more.

  • avatar
    rachel / Reply

    I remember the clay hadn’t absorbed much water in the 5 minutes we were given ,but the moss had.

    • avatar
      Margaret Ptak / Reply

      Yes! Very true! That’s why companies sometimes add moss to soil which you can purchase from stores. This helps the soil absorb more water for plants which need “wetter” soil to grow.

  • avatar

    I remember that some things didn’t absorb that much water in 5 minutes like the clay

    • avatar
      Margaret Ptak / Reply

      Great observation Jahlyn! The clay would take the longest time to absorb the water AND to remove the water. This knowledge is actually super useful for scientists — they use clay on the very bottom of landfills to trap and prevent all the liquids and decomposing matter from our landfills from reaching our drinking water

  • avatar
    Julianna / Reply

    It was so fun to inhale the water with the little water inhaler and even though I had the dirt it was still really fun today to inhale the water.!

    • avatar
      Margaret Ptak / Reply

      Hi Julianna! I was wondering what you meant by “little water inhaler” and then I realized, you’re talking about pipettes! I don’t believe we’ll be using them again this year, but they become very handy in chemistry lessons.
      Happy you enjoyed learning how to use a pipette during our soils lesson!

  • avatar
    ella / Reply

    I remember when we used the water pipette with the soil it mixed all together and the water turned brown so it was harder to get most of the water out in 5 minutes.

    • avatar
      Margaret Ptak / Reply

      Yes Ella, that’s one problem a lot of scientists face actually! Pure extractions and separations can be quite difficult and usually leave some of the product behind. If you have ever baked or made pancakes, you may have noticed that there is almost always some batter left behind! There are a lot of complicated techniques (more complicated than using a pipette!) that scientists use to create purer separations.
      Great observation!

  • avatar
    Mrs. Merdin / Reply

    I’m glad that what stuck out in your minds is how moss absorbed a lot of water and clay did not. Remember, the point of the activity was to see how the size of the particles impact the different types of soil. The spaces between the clay are very tiny. When it is dry, it is almost as hard as concrete. Plant roots can’t push through it and the water particles are not absorbed by it.

  • avatar
    NATALIE / Reply

    when my table mate put the water in the sand, when my table mate took out the water for some reason and my table mate took the most water out of the sand.

  • avatar

    the dirt on soil was really fun the soil in my group was a little tough than I thought the soil obsoarb a lot of water the sand didn’t obsoarb that much water the moss has a little a lot of water and the clay that was dry did not obsoarb water since it was solid.

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