Types of soil

Back to: BIOLOGY NEW LOWER SECONDARY CURRICULUM BOOK 2

learners have to appreciate that the appearance of soil varies from place to place; you can make them think about the appearance of soil from different parts of their environment and note the differences.

Activity 1.1 Identifying types of soil samples

Key question: what are thedifferenttypes of soil?      

What you need

• Three soil samples: A, B and C
  Water                    •   Stirring rod
• Transparent beaker and a large  bottle or a measuring cylinder

Measuring instrument for example a ruler or a tape measure

 What to do

1. In groups, half fill the measuring cylinder with soil sample A and using a tape measure or a ruler, measure the level of
   soil in the measuring cylinder. Record the measurement as total soil.
2. Add water until the measuring cylinder containing soil is two-thirds full. Notice the air bubbles coming out of the soil.
   What does this tell you?
3. Cover the opening of the measuring cylinder using your palm or a lid. Shake it vigorously for about two minutes until all the particles are separated by the water. Place the measuring cylinder down and allow the soil to settle.
4. After 1 minute, measure the amount of soil in the bottom of the measuring cylinder. Record this measurement and label it as the “sand fraction.”
5. Allow the sample to settle for 30 to 40 minutes, then measure again and record the level. This second layer indicates the silt fraction of the soil.
6. Determine the amount of clay in the soil by subtracting the combined sand and silt measurements from the total soil measurement.
7. Convert the measurements into percentages and repeat the procedure (1-5) above for soil samples B and C.
8. Record the percentage of each fraction of the soil samples in a suitable table.
9. As you wait for soil samples to settle, use the remaining portion of the soil samples  to  carry  out  the  following procedure:

i) examine soil samples A, B and C and note the colour of each sample,

ii) obtain a small portion of each soil sample, wet it with a small amount of water, and  rub the wet sample between your thumb and your first finger. How does each sample feel?

From the observations above and with guidance from figure 1.1, i) name the type of soil from which soil samples A, B, and C were obtained? Give a reason for your answer in each case, ii) Identify the areas in your community where each type of soil named above is likely to be found. Write a  report of your findings and present it to the rest of the class.

Figure 1.1: Common types of soil: (A) loam soil (B) sandy soil (C) clay soil

Suggested responses

Observations

1. Loam soil. This is a mixture of sand (about 40%), clay (15%), and organic matter (1-4%). It is dark and has a stable crumb
   structure.
2. Sandy soil. It is light and has a gritty feel when wet.
3. Clay soil, it is heavy and has fine particles with a sticky fee! when wet.

ii) Loam soils are usually found almost everywhere especially in gardens, near compost pits and dumping areas.

•   Clay soil  is found  in swamps and anthills.

•  Sandy soil is found on lake shores and hilly areas.