Soil System

Soil Importance

• Essential to how ecosystems work– Source of nutrients– Basis for root systems– Habitat for millions of plant and micro- and

macro-organisms– Acts as filter, recycling system, and pollution

control mechanism

Soil Components

• Broken down rock– Sand, silt, clay, pebbles, or other rock

• Organic matter– Old leaves, dead animals or plants

• Water

• Air

Soil Formation

1. Breakdown or weathering of rocks– Caused by the actions of water, wind, or ice

2. Presence of living organisms

3. Decomposition of dead organisms

Soil ProfileThe O layer – high quality organic matter,

with living and dead organisms in different stages of life and decomposition. Usually dark in color due to rich humus layer form the decomposition

The A level – also called the upper soil layer and contains plant roots, bacteria, fungi, and other decomposers

The B layer – contains less oxygen due to depth below the surface so has fewer roots and living organisms

The C level – consist of sand, clay or pebbles and rock. Very little living or dead organic matter. Often Yellow or orange

O horizon

A horizon

B horizon

C horizon

Soil Composition

Name Particle Diameter

Very coarse sand 2.0 to 1.0 millimeters

Coarse sand 1.0 to 0.5 millimeters

Medium sand 0.5 to .25 millimeters

Fine sand .25 to .10 millimeters

Very fine sand .10 to 0.05 millimeters

Silt 0.05 to 0.002 millimeters

Clay Below 0.002 millimeters

Soil Texture Triangle