Formation of Soil UNIT 5 STANDARDS: STATE OBJECTIVES: NCES 2.1.1, 2.1.3, 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 cm Abundance of Humus Rich soils Less deep Less fertile Rich clays Less than 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