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 a 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 and 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