Soil Functions

© 2007 Donald G. McGahan (aka soilman) All Rights Reserved

  1. Medium for plant growth
    • source of support, nutrients, water, and air.
  2. Recycling of raw materials.
    • organic wastes are broken down and nutrients are released.
  3. Habitat for soil organisms.
    • a handful of soil contains billions of organisms from thousands of species.
  4. Regulator and purifier of water supplies.
    • water storage and cleansing.
  5. Engineering medium.
    • as building material and structural support.
  6. Atmosphere modification.
    • controls on composition of atmosphere.

What is a typical soil composed of?

  • Approximately 50% solids and 50% pore space
  • Mineral (inorganic) materials - decomposed rocks (45-50% - percent by volume)
  • Organic materials - remains of plants and animals (0-5%)
  • Water (20-30%)
  • Air (20-30%)
  • There are about 19,000 different soils identified in the USA alone. In order to compare and contrast them, we must be able to describe them in a systematic, accurate and concise way

Support for Plant Growth

  1. Physical support
  2. Aeration for roots
  3. Moisture supply and storage
  4. Moderation of root zone and near-ground air temperature
  5. Provide and maintain an environment relatively free of phytotoxins
  6. Nutrient Resources
    • 13 of the 17 essential nutrient elements

Usually animals and people obtain their mineral nutrients indirectly from the soil via consumption of plant materials.