© 2007 Donald G. McGahan (aka soilman) All Rights Reserved
- Medium for plant growth
- source of support, nutrients, water, and air.
- Recycling of raw materials.
- organic wastes are broken down and nutrients are released.
- Habitat for soil organisms.
- a handful of soil contains billions of organisms from thousands of species.
- Regulator and purifier of water supplies.
- water storage and cleansing.
- Engineering medium.
- as building material and structural support.
- 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
- Physical support
- Aeration for roots
- Moisture supply and storage
- Moderation of root zone and near-ground air temperature
- Provide and maintain an environment relatively free of phytotoxins
- 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.