Importance and Formation of Soil
oVERVIEW
INSTRUCTOR:
UNIT: Identification of the Nature and properties of Soils and Soil Formations
LESSON: Importance and Formation of Soil
IMS REFERENCE:IMS #8380
Lesson Plan
LESSON OBJECTIVES
The student will be able to:
- recognize importance of soils to the nation;
- explain the importance of soils to the state;
- identify and discuss the factors of soil formation; and
- discuss relationships among soils, plants, and animals.
TOols & equipment
- Computer(s) with internet access
Key Terms
“C” Horizonresidual
horizonsoil
leachedtemperature
percolationweathering
permeable
TEACHING MATERIALS AND RESOURCES
- IMS #8380
- Class Notes for IMS #8380
- Lesson Test for IMS #8380
- Activity Sheet for IMS #8380
- PowerPoint Presentation for IMS #8380
TEACHING PROCEDURES
Preparation
Key Points / MethodsLink:
Have the students walk outside and look at their surroundings. Identify all the purposes of soil in their own environment.
Motivation:
Ask the students to…
- Verbally give reasons why soils are important to the United States and agriculture.
- Verbally give reasons why soils are important in Texas.
Overview:
In this lesson, the students will:
- recognize importance of soils to the nation;
- explain the importance of soils to the state;
- identify and discuss the factors of soil formation;
- discuss relationships among soils, plants, and animals.
Teacher Led Discussion with Student Response
Student Thought and Reflection
Review Objectives
Presentation
Key Points / MethodsIMPORTANCE OF SOIL
United States’ greatness is due to the productive capacity of the soils; one of the few nations that produces enough food and fiber for its own use and exports products to other countries
Soil:
- acts as a habitat for soil organisms
- an engineering medium
- system for water supply and purification
- original source of most nutrients for all plant and animal life
- acts as a continuous recycling system for nutrients, organic waste
- provides nutrients for plant growth
- decaying plants return nutrients directly to the soil
PERMANENCE OF SOILS
Soils appear to be permanent and unchanging. In reality, soils are very dynamic; formation of soils takes place over long periods of time; changes must balance each other in order to maintain productivity of soil
FORMATION OF SOILS
Soil formation:
- based on the weathering of rocks and minerals; Physical and chemical decomposition eventually break down rocks and minerals into the mineral matter component of soil;
- slow process that takes place over long periods of time (100 to 900 years); average, about 100 years to develop one inch of topsoil
The kinds of soils formed at a particular site are determined by the interaction of (1) climate, (2) living organisms, (3) parent soil material, (4) topography, and (5) time. Different combinations of these factors lead to the formation of different soils.
Verbally list the five determinants of soil type.
Climate
Climate: average course of weather at a particular place; exhibited by temperature, wind velocity, precipitation
Temperature and precipitation greatly affect the rate of weathering. When temperature rises, the rate of chemical reaction increases and growth of fungi, soil bacteria and plants increases.
How does rainfall affect the soil?
Adequate soil moisture also aids chemical reaction and growth of plants, fungi, and bacteria; too much water retards microbe growth
Percolation: movement of water through the soil; carries minerals and organic matter through horizons
Horizon: soil producing layers
In areas of high rainfall, the soils are usually leached and acidic; intensity of rainfall greatly influences soil erosion, particularly on sloping topography.
Low humidity, high winds dry out soils, reducing chemical reaction and microbe growth; High winds cause significant erosion on some unprotected soils
Using the internet. Collect data on rainfall and temperature for your local area. Include data on mean annual precipitation, temperature, and length of growing season.
What activities performed by humans can disturb soil formation?
Living Organisms
Living organisms: exert considerable influence upon the formation of a soil.
Types of bacteria and fungi aid in soil formation by breaking down organic materials.
Insects, “insect-like” creatures and animals contribute to the formation on soils by breaking down and mixing the various soil materials.
Human activities (land clearing, cultivation) remove natural vegetation and disturb structure of the topsoil.
Parent Material
Type of parent materials from which a soil is formed can influence: texture, structure, color, fertility of the soil
Clay soils form from easily weathered materials; sandy soils form from more resistant materials
Topography
Topography can have a direct effect on soil formation through erosion.
Sloping land: loose material moved downward by runoff and gravity; movement breaks up soil materials and deposits them at lower levels while exposing subsoil materials along the upper slopes.
Topography can indirectly affect soil formation through its impact on percolation and drainage.
Sloping land tends to have more runoff from rainfall, resulting in less percolation of water through the soil.
Soil in a location that collects surface water may tend to be saturated; leads to less biologic chemical activity.
Time
Soils form by the chemical and physical weathering of parent material as affected by climate, living organisms, and topography over time.
Chemical weathering: result of chemical reactions between water, oxygen, carbon dioxide, and other substances upon soil materials.
Physical weathering: mechanical forces such as freezing, thawing, wind and water erosion, gravitational movements that physically break down materials into smaller particles.
Weathering causes soils to develop, mature, age; Plant nutrients are released quickly from minerals, plant growth increases, organic matter accumulates.
Soluble nutrients are lost from the soil through leaching; as supply of nutrients in the soil decreases, amount of plant growth is reduced to point that organic matter decomposes faster than it is produced.
Permeable soils: fine clay particles tend to move downward from soil surface into subsoil; through more advanced stages of weathering, soils slowly decline to lower and lower levels of production.
Climate, living organisms, parent material, topography, and time impact soil formation and changes in soil composition. Variations in these factors have resulted in the wide variety of soils that are present today.
Using the Maroon River erosion scenario activity, calculate the amount of silt transported by a river in one day, how much soil is lost in one year, and convert this to acres. Use internet conversion websites for assistance. / Presentation A
Student Review
Student Thought and Reflection
Factors Impacting Soil Formation Activity
Student Thought and Reflection
Maroon River Erosion Scenario
Application
Key Points / MethodsFactors Impacting Soil Formation Activity
- Using the Internet, collect data on rainfall and temperature for your local area. Include data on mean annual precipitation, temperature, and length of growing season. Discuss how these factors effect soil formation in your area.
- Using the Maroon River erosion scenario from the Activity Sheet for IMS #8380, calculate the amount of silt transported by a river in one day, how much soil is lost in one year, and convert this to acres. Use Internet conversion websites for assistance.
Scenario
Evaluation/Summary
Key Points / MethodsComplete Lesson Test for IMS #8380 / Worksheet
references/ Additional matierials
Australian National University Forest Science Conservation and Management. (2000). ANU Forestry. [Online]. Available:
Brady, N. & R. Weil. The Nature and Properties of Soils. Upper Saddle River, NJ: Prentice Hall, 1999.
Natural Resource Conservation Society. (2000). Natural Resource Conservation Society. [Online]. Available:
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