Formation of Soil

UNIT 5

STANDARDS:

STATE OBJECTIVES: NCES 2.1.1, 2.1.3, 2.1.4

LESSON 3

Lesson Objectives In this lesson, you will learn about:

How soil forms The relationship between organic and

inorganic components in the soil Be able to identify some soil characteristics Recognize soil horizons in a soil profile

Development of Soil What is soil? Soil is the loose covering of

broken down rock particles and decaying organic matter overlying bedrock.

Soil is the result of chemical and mechanical weathering.

Bacteria and fungi break down organic material adding nutrients to the soil.

Basic Process of Soil Creation Role of Bacteria

Role of Nutrients

Soil Texture

Water retention

Simple comparison

Bacteria break down organic material

Nutrients in the soil aid in plant growth

Texture refers to grain size (sandy…clay)

Water retention increases with organic material

Compare potting soil to sand

Soil Composition What is parent soil?

What is transported soil?

Parent soil comes from the weathering of the underlying bedrock into smaller pieces. This determines the basic mineral composition.

Transported soil is soil that has been moved from its origin to the section of soil. Erosion is the main agent of soil transport.

Soil Profile What is a soil profile?

What are the different layers?

What are the 3 soil horizons?

A soil profile is a vertical sequence of soil layers.

Each distinct layer of the soil is called a soil horizon.

Horizon A: Rich organic material and humus.

Horizon B: generally characterized by rich clays, no water loss.

Horizon C: Sits on bedrock and is weathered bedrock.

Parts of the Soil Profile

Horizon O

Horizon A

Horizon B

Horizon C

Horizon R

Soil Types What determines the

different soil types?

*Soils are classified based on the climate.

Soils form from parent bedrock.

Plants and animals living in and on the soil.

Length of time soil has been forming.

Climatic conditions

Polar Soils Characteristics

What is permafrost

Form at high altitudes Greenland, Canada, Antarctic Good drainage NO distinct horizons Very shallow, few inches

Permanently frozen ground

Temperate Soils Characteristics

Grasslands

Forests

Praries

Great Plains to forests Annual rain 50-60 cm

Abundance of Humus Rich soils

Less deep Less fertile Rich clays

Less than 50-60 cm rain Only support brush

Examples of Temperate Soils

Desert Soils Characteristics Receive low amounts

of rain < 25cm per yr High levels of salts Little to no organic

material Light colored Course grain, sand

Tropical Soils Characteristics High Temperatures

High rainfall Often infertile due to

high levels of plant acids and salts

Little humus Little nutrients *Remember rain

washes it away

Soil Fertility What is fertility How well the soil can

support the growth of plants.

Mineral content and nutrients determine

Commercial fertilizer Compost Mulch and Peat

Lesson Review Synthesis: Explain the stages involved in

soil formation Application: Describe three characteristics

of soil Evaluation: Explain the difference between

temperate and tropical soil Relativity: Investigate the cost to fertilize a

yard (40,000 sq. feet) using 10-10-10