SOIL-LAYERS OF SOIL

SOIL FORMATION AND COMPOSITION

by Geetika Sharma

Poll

Do you feel that soil is an important natural resource and we all directly or indirectly depend on soil?

• What is soil?

• ​Soil is an important natural resource.

• ​Complex mixtures of minerals, water ,air and organic matter.( Humus)

• How it is formed?

• ​Soil is formed by breaking up of rocks.

​

Our Previous Knowledge- What do we already know?

​Learning Outcomes

Students will be able to

​1. Learn about the four main components of soil.

​

​2. Identify organic and inorganic matter of soil.

​

​3. Understand the formation and layers of soil.

​Learning Objectives

​

​1. Four main components of soil

​

​

​2. Organic and Inorganic matter of Soil.

​

​3. Formation of Soil

​

​4. Layers of Soil

​Soil is made up of FOUR components:

​

• In Organic ​Mineral matter (45%)

• ​Organic material (5%)

• ​Water (25%)

• ​Air (25%)

​Soil Consists of....

1. Inorganic Mineral Matter- ROCKS​

   Gravel

2. Stone

3. Sand

4. Clay

5. ​Silt

1. ​Organic Matter

   Humus​

​

    Clay

​

1. ​Feels sticky

2. ​Yellow/red in color

3. ​Poor drainage

4. ​SMALLEST particle size

5. Usually found in Plateaus

Sand

​

1. ​Feels gritty

2. ​More of a gray or white color

3. ​

   Poor fertility (roots can't grip; not enough water or humus)

4. ​LARGEST particle size.

5. ​​Usually found in Deserts

1.      Silt

   ​Feels soft/smooth

2. ​Brownish/black in color

3. ​Larger than clay,

4. but smaller than sand

   It is very fertile

5. In India it is mostly found in northern plains.​

​Humus

​

1. ​It is an organic matter made up of waste from animals and dead leaves/plants which help us to make the soil fertile.​

2. ​We can add humus to inorganic mineral soil to make it more fertile.

​LAYERS OF SOIL

1. O horizon-humus on the ground surface.

2. ​A horizon - Top Soil, rich in organic material.

3. ​B horizon -Subsoil, less organic material than topsoil, we can find deep root of plants in this zone.

4. C horizon- Parent material​ , slightly weathered rocks, no organic matter.

5. R horizon-Bedrock​ , Unweathered rock material.

​

​

Poll

ARE YOU READY TO TAKE THE QUIZ ?

​EXIT CARD

​

​READ THE QUIZ QUESTIONS CAREFULLY AND TICK THE CORRECT ANSWER.

​TIME- 30 SECONDS FOR EACH QUESTION

Multiple Choice

This soil is gritty ,cannot hold water and has poor fertility.  identify the soil.

• Sand

• Silt

• Humus

• Clay

Multiple Choice

What is a soil horizon?

• a factor influencing how soil is formed

• a technique used to map soils

• a layer of soil

• an organism found within soil

Multiple Choice

Which three layers form the soil profile?

• air, water, and soil

• minerals, organic matter, and living organisms

• clay, silt, and sand

• topsoil, subsoil, and parent material

Multiple Choice

How does a silt soil feel to the touch?

• Smooth and Light

• Gritty

• Sticky

• Rocky

Multiple Choice

Why is organic matter (humus) an important part of soil?

• It helps to improve water infiltration.

• It can break down organic pollutants

• It converts nitrogen in the air into nitrates used by plants.

• It is rich in nutrients, which is important for fertility

Multiple Choice

Which of the following is the horizon in which we find the partially weathered rocks?

• Parent Material

• Bedrock

​HOME TASK

​DRAW A WELL LABELLED DIAGRAM OF LAYERS OF SOIL IN YOUR NOTEBOOK.

​THANK YOU :)