Introduction to Agriculture, Food, and Natural
Resources
1
Introduction to Agriculture, Food, and Natural
Resources
How Soils are Formed
Unit 3 – Lesson 3.3 Starting from the
Ground Up
2
Five Formation Factors
The basis of all soil will be derived by or
aided in development by the following
factors:
Climate
Organisms
Parent Material
Time
Topography
3
Climate
Climate includes several forces that act
upon soils, which breakdown rock into
smaller fragments and eventually down to
small particles.
Rainfall
Temperature
4
Organisms
If conditions are appropriate to support
plants and soil dwelling animals,
organisms thrive and assist in creating
optimal soils for plant production.
5
Parent Material
• Parent material is the substance from
which soil is created.
• In most cases, soil is formed from a type
of rock that has been broken down by
weathering or chemical processes.
6
Time
• Soils develop at varying rates depending
upon the climate and other formation
factors.
• The forces that form a given soil indicate
how long it took the soil to be formed.
7
Topography
What would soil be like on top of a hill
compared to the bottom of the hill?
Top – larger particles and less organized
Bottom – smaller particles and deep
Why?
8
Soil Development Classifications
There are four main ways that the
process of soil formation occurs:
Addition – accumulation or deposition
Reduction – leaching and erosion
Translocation – movement within soil profile
Transformation – soil changes in place by
weathering or microorganism conversion
9
Erosion
• The opposite of soil formation is erosion,
which has a detrimental effect on soil.
• Erosion comes in two forms:
Water
Wind
10
Erosion Happens
In what circumstances is soil erosion more
likely to happen?
•
•
•
•
•
Steep ground
Too much irrigation
Working soil in a rainy season
Not protecting soil with ground cover
Allowing wind to blow across worked soil
11
What happens when the soil is gone?
• Poor crop production
• More inputs are required like water and
fertilizers to grow crops
• Soil could be unusable in some cases
12
References
Huddleston, J. H., & Kling, G. F. (1996).
Manual for judging Oregon soils. Corvallis,
OR: Oregon State University.
Parker, R. (2010). Plant and soil science:
Fundamentals and applications. Clifton
Park, NY: Delmar.
13