1. Soil Formation and Components
Basic Soil Science
AFNR-BAS-6: Describe soil formation and management and assess its relevance to plant/animal production and natural resources management.

2. Soil Formation formed from parent material
Rocks: weathered or eroded into small particles like sand and silt
weathering: wear away or change the appearance or texture of something by long exposure
Organic Matter: small creatures and plants die over time in layers forming clay soils

3. Major Factors that Control the Type of Soil that Forms
Climate
Organisms (plant or animal)
Landscape
Parent Material
Time

4. Soil Components Minerals
made up of rocks and minerals of various sizes (sand, silt, and clay)
provides texture to soils
about 45% of an ideal soil

5. Soil Components Organic Matter
plant, animal, or microbes that may be new to the soil or fully decomposed
stabilizes the soil, aids in plant growth, stores/supplies nutrients, limits soil compaction, holds carbon, and limits the impact of pollution
5% of ideal soil

6. Soil Components
Water
fills spaces around soil particles (called pores or pore spaces)
available for absorption by plants
25% of ideal soil

7. Soil Components Air spaces between particles
allows gases, water, and organisms to travel and transfer through the soil
25% of ideal soil

8. Soil Components

9. Soil Particles
Soil is made of three major components (a.k.a. soil particles)
sand: the largest particle
silt: the intermediate-sized particle
clay: the smallest particle
soil texture is determined by the percentage of each particle type (for example: sandy clay, clay sand, silty clay...)

10. Layers of Soil soil horizons: layers of soil
differ in a number of easily seen soil properties such as color, texture, structure, and thickness
soil profile: the arrangement of the soil horizons

11. Soil Horizons R Horizon: solid rock also known as “bedrock”
lowest layer

12. Soil Horizons C Horizon: weathered parent material and broken rock
very few (if any) roots found here

13. Soil Horizons B Horizon: accumulation of leached materials
some tree roots are found in this layer
lighter in color than the A horizon and very dense
also known as “subsoil”
leaching: the loss of nutrients and materials that have been dissolved as they move through soil

14. Soil Horizons A Horizon: rich in nutrients and minerals
most roots are found here
usually dark in color
also known as “topsoil”

15. Soil Horizons O Horizon:
contains organic material in the form of fresh and more decomposed plants and animals as well as microbes
very top layer
usually thin
also known as “humus”

16. Soil Ecosystems are Important
a scoop of soil can contain thousands of organisms that help determine the quality of the soil and ultimately, plant health
contains earthworms, insects, burrowing animals, and microorganisms
these components, along with the non-living matter in the soil, break down organic matter, recycle nutrients, and help plants grow
provide physical support to anchor plants in the ground and help support the base of the plant so it can grow upward
holds water like a sponge and releases that water as plants and animals need it
Water is filtered as it travels through the soil
removes toxins and foreign matter

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