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The Nature of Soil
Explain how the resources soil provides help in
supporting life; Explain the contents of soil; Describe the biological nature of soil; and Describe four ways plants use soil.
Objectives
Soil provides many resources to life
They make it possible for plants and animals to grow
We will list five of them
Soil Supports Life
Oxygen
In the soil Needed for root growth
Temperature Soil absorbs heat from the sun Soil radiates heat into the atmosphere
This cycle regulates the temperature so seeds can germinate and grow
Soil Supports Life
Water
Used by growing plants
Carbon The base of all life forms Most essential element to life
Nutrients Minerals that are absorbed and used by the
plant
Soil Supports Life
Soil is composed of four primary components
Mineral matter Organic matter Air Water
In addition, there are numerous living organisms
Contents of Soil
Soil is 50/50 solid and porous
What is porous?
Solids Mineral matter and organic matter
Contents of Soil
Solids
Mineral matter 45%of the soil Broken down rocks Sand, Silt, Clay
These three things determine water holding capacity and fertility of the soil
Contents of Soil
Solids
Organic Matter 5% of the soil Mostly from leaves, roots and stems Contributes to water holding capacity and fertility Gives soil a dark color
Contents of Soil
Pore Spaces
Space occupied by air and water
Air ≈25% of soil
Water ≈25% of soil
Contents of Soil
Air
Constantly fluctuating More water = less air Less water = more air
Contents of Soil
Water
It can do two things with soil Run off Soak in
Contents of Soil
Terms to know
Infiltration Water soaking into the soil
Percolation Water moving downward through the soil
Permeable Quality of soil when water can both infiltrate and percolate
Leaching Movement of dissolved minerals and chemicals and salts
downward with water
Contents of Soil
3 types of soil water
Gravitational water Water pulled down by gravity Causes leaching
Capillary water Water held in pore spaces May move sideways or up
Hygroscopic water Water that forms a thin film around soil particles Not available to plants
Contents of Soil
What life forms would you find in the soil?
Worms Insects Bacteria Fungi Other organisms
Biology of Soil
Bacteria and fungi have an important role in
the soil. They break down organic matter and release
nutrients.
Biology of Soil
Earthworms, ants, crawfish, moles, and other
organisms improve the soil tilth, Tilth: the ease at which soil can be worked. These organisms create openings in the soil as
they tunnel. This enhances drainage and improves air
exchange.
Biology of Soil
What are they?
Anchorage Water Oxygen Nutrients
4 ways plants use soil
