Soil Lab: Investigating the Earth

The Good EarthSoil is a natural resource like coal, air, and water. Scientist believe it takes mature 600

years to make 1” (2.5 cm) of rich soil. On and in this rich soil live many forms of plant and animal life. The limited amount of good soil available is vital to our survival.

Our environment begins with soil beneath us. Conservation of the soil is essential if we are going to maintain high standards of living and provide for expanding populations. Our soils can become polluted by the careless addition of chemicals and by improper water drainage. They can be destroyed forever by wind and water erosion or by the intrusion of the sea.

Soil ProfileWater can be used to separate the different sized particles on soil. Place three teaspoons (15ml) of soil in a tall test tube. Add water to the two-thirds level. Cork the tube and shake vigorously for one minute. Allow the tube to stand upright without shaking for five minutes.

In five minutes your test tube of soil should have separated into layers.

1) Describe the differences between the top and bottle soil layers. Look at what type of material makes up each layer.

**Save this test tube for the “How Sour is Your Soil” section.

How Sour is Your Soil

Vinegar tastes “sour” and is conserved and acid. Soap tastes “bitter” and is considered a base. Soils can be chemically acid or base. Some plants can’t live in soil that is too acid or base. The graphic above shows a pH scale use to measure acids and bases. You will be shown how to use pH paper.

Remove the cork from the test tube used previously. Dip the end of your pH paper into the clear water at the top of the test tube.

2) What color did the pH paper turn?_______________________________________________

3) What is its number on the pH scale? _______________________________________________

4) Is your soil acid, base, or neutral? _______________________________________________

**Clean out your test tube shaking the contents vigorously again and then pouring the contents out outside. Rinse the test tube several time outside before cleaning it in the sink with soap.

There is More Than Dirt in Soil

Place approximately one teaspoon (5ml) of rich dry soil in the bottom of a Petri dish. Spread it evening along the bottom. Cover with the Petri dish lid. Place the covered dish in the sunlight for a few minutes.

After a few minutes observe the dish without removing the cover.

5) What do you observe on the lid of the Petri dish that was not present before?

6) Where must this substance have come from?

7) Using your previous knowledge of soils, explain why it is necessary for good soil to contain this substance. Please give a specific example.

How Fast Does Your Soil Drink

Soils differ widely in their ability to absorb water. Sandy soils pass water through very quickly. It is difficult for water to penetrate clay soils. Soil that is loosely packed can absorb water much quicker than soil that has been compacted. Let’s find out how long your school soils takes to absorb water.

Choose an area outside of the school that gets very little traffic from students or visitors. Clear off any grass or ground cover so that you can see the soil.

Obtain a can from your teacher that is open at both ends. Measure ~ 3 cm from the bottom of one end and make a mark all the way around the can to show this distance.

Using the block of wood and hammer press your can into the soil as shown by your teacher.

Pour 100mL of water into the embedded can and time how long it takes for water to penetrate.

Make observation as the water is being absorbed into the soil. You will need these observations to answer the questions below.

Stop timing when you see a muddy surface or after 5 minutes.

Record the time in minutes or seconds in the data table below.

Repeat the entire procedure in a high traffic area using the same can.

Location Description of site and soil Time for water to percolate into the soil

Low traffic area

High traffic area

8) What do you observe bubbling out of the water as it percolates into the soil?

9) Where must this substance have come from?

10) Why is it necessary for good soil to contain this substance? Give at least one specific reason.

11) Of the two sites tested, which had the most rapid percolation? Why do you think this is?

12) Of the two sites tested, which had the slowest percolation? Why do you think this is?

13) Which site seemed to have the most healthy plant growth? Why do you think this is?

Summary Questions

14) List several ways that soil may become compacted?

15) In what ways might soil compaction increase soil erosion?

16) What should be done to reduce soil compaction on school campuses or in public places?

17) What should be done to reduce soil compaction in wilderness areas?