SOIL Describe how soil forms. Explain the characteristics of soil. Distinguish between factors that affect soil development.

The Nature of Soil What is soil and where does it come from?

The Nature of Soil A layer of rocks and minerals covers the Earth’s surface. Weathering breaks down rocks into smaller and smaller pieces. These fragments become high quality soil after plants and animals live in it. Plants and animals add organic matter. Question: What is organic matter? Leaves, twigs, roots, dead worms, insects, and etc.

The Nature of Soil Soil: A mixture of weathered rock, decayed organic matter, mineral fragments, water and air.

The Nature of Soil Question: How long can it take for soil to develop? Thousands of years

The Nature of Soil Factors that can affect soil formation. Climate Slope of land Types of rock Types of vegetation Amount of time rock has weathered.

The Nature of Soil Composition of soil: Where does the organic material in soil come from? Most organic material comes from plants. Animals and microorganisms provide additional organic material.

The Nature of Soil After plant and animal material gets into the soil, fungi and bacterial cause it to decay. The decayed organic matter turns into humus.

The Nature of Soil Horizons: Different layers of soil. Soil Profile: All the layers of soil.

The Nature of Soil A Horizon: Top layer of soil. Might be covered with litter. Litter: Consists of leaves, twigs, and other organic material. Eventually changes to humus by decomposing.

The Nature of Soil B Horizon: 2nd layer, lighter in color, contains less humus, less fertile. Contains material moved down from A horizon by the process of leaching.

The Nature of Soil Leaching: Removal of minerals that have been dissolved in water.

The Nature of Soil C Horizon: Bottom of soil profile. Consists of partially weathered rock. Often the thickest layer. Does not contain much organic matter. Question: What would be below the C Horizon? Rock

The Nature of Soil Soil Types Reflect Climate: Different climates have different soils. Soil temperatures and moisture affect the quality of soils. Question: Which would have more organic matter; deserts or prairies. Desert soils contain little organic matter and are thinner. Prairie soils have thick A horizons.