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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
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