Soil What is soil The loose weathered material

Soil

What is soil? �The loose, weathered material on Earth’s surface in which plants can grow.

What is the main ingredient? �The main ingredient for soil is the solid layer of rock beneath the soil called bedrock.

Soil Composition �A mixture of rock particles, minerals, decayed organic materials, water and air. �Known as sand, silt, clay and gravel

What is humus? �Decayed organic material in soil from plant and animal remains �Provides spaces in soil for water and air �Also contains many nutrients that plants need to grow �Often dark in color

Soil Fertility �The measure of how well soil supports plant growth �Soil rich in humus has a high fertility content �Sandy soil has low humus and an low fertility content

Soil Texture �Depends on the size of soil particles �Sand feels coarse and grainy �Clay feels smooth and silky �Silt is dry or moist and sticky �Classified by size (smallest to largest) • • Clay Silt Sand Gravel

What is loam? �Soil that is made of equal parts clay, silt and sand holds air and water

Process of Soil Formation �Soil forms as rock is broken down by weathering and mixes with other materials on the surface �Soil is constantly being formed whenever bedrock is being exposed �Soil forms into horizons or layers

What is a soil horizon? �A layer of soil that differs in color and texture from the layers above and below it

What are the different soil horizons and what are their characteristics? �Horizon A- topsoil- a crumbly, dark brown soil with a mixture of humus, clay, and other materials �Horizon B – subsoil- clay and other particles washed down from A, little humus �Horizon C – weathered rock

Soil Horizons Horizon A Topsoil Horizon B Subsoil Horizon C Bedrock

What are soil organisms? �These living things make humus and other materials that makes soil fertile �These creatures mix the soil and make spaces for water and air

What is litter? �The loose layer of dead plant leaves and stems on the soil surface

What are decomposers? �Organisms that live in soil and turn dead organic material into humus �Includes fungi, bacteria, worms and other small animals or bugs �Worms do most of the work, they eat their way through the soil and carry soil between layers, the waste is enriched with nutrients