Soil – Part 1

Soil is a layer of material covering the earth’s surface from which plants grow and obtain water, air nutrients and anchorage.

The constituents of soil include; particles of sand or clay (inorganic materials), water, humus, air, dissolved salts and living organisms.


Living organisms:

These are of two types, the microorganisms and microorganisms.

 Microorganisms are those that are too small to be seen by a naked eye; they are microscopic organisms. These include bacteria, fungi, algae, protozoa, nematodes among others

Importance of microorganisms in soil

  • The microorganisms breakdown organic matter and humus into soluble substances that can be taken up by plants. They enable recycling of nutrients in soil.
  • When they die, they also add to the nutrients in soil
  • Some of them such as bacteria convert Nitrogen (atmospheric) to organic Nitrogen compounds which can be used by other organisms.


  1. Define soil
  2. Mention the six components of soil
  3. What are microorganisms? Give two examples of microorganisms
  4. List two importance of microorganisms in soil