1. Soil Science

2. Soil Categories Topsoil Subsoil Parent Material
The upper most layer found in the soil profile.
Contains living and non-living material.
Animals, bacteria, plants, minerals, soil particles and organic matter.
Subsoil
Second layer found in the soil profile.
Contains much of the same material as topsoil but lacks the organic matter found in the topsoil.
Parent Material
Last layer found in the soil profile.
Made of different rock or plant formations
Limestone, Sandstone, Garnet, and Peat

3. Soil Formation
Soils are formed from the weathering of the parent materials.
There are two types of weathering that affects soils.
Physical Weathering
Parent material is directly exposed to the weathering affects of the atmosphere.
Water, Ice, Snow, Wind, Waves and Gravity
Chemical Weathering
Effects of atmospheric chemicals or biologically produced chemicals on the parent material.

4. Soil Makeup Soil is made up of four major components. Sand Silt Clay
Minerals

5. Soil Makeup Sand Largest of the soil components.
Range in size of 2.0 to .05 mm.
Drains rapidly.
Course in texture.

6. Soil Makeup Silt Second smallest of the soil components.
Range in size from .063 to .002 mm.
Can be a soil, a suspended sediment in surface water, or found on the bottom of a body of water.
Moderate drainage.

7. Soil Makeup Clay Smallest of the soil components.
Formed from chemical weathering of other soil components.
Drains very slowly.

8. Soil Makeup
Minerals
There are 16 nutrients that are essential for plant growth and reproduction that are found in soil.
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Potassium, Sulfur, Calcium, Iron, Magnesium, Boron, Manganese, Copper, Zinc, Molybdenum, and Chlorine.

9. Soil Ecosystem
Relationship between the living and nonliving material found in the soil.
An example of this can be found in the Nitrogen cycle

10. Land Use Classification
Agricultural land can be classified as eight different land capability classes, which determines the final three land use classes.
The three land use classes are:
Row Crop – used to produce many different agriculture products
Pasture – used for the production of grazing animals and forage production
Forest – used for the production of trees and wildlife habitat.

11. Land Capability Classes
The eight land capability classes allow for the classification of the land and their end use.
Row Crops
Class I – used for row crops with few limitations
Class II – used for row crops with some limitations
Class III – used for row crops with many limitations
Class IV – used for row crops with major limitations

12. Land Capability Classes
The eight land capability classes allow for the classification of the land and their end use.
Pasture
Class V – areas that are level, but subject to flooding, Used for pasture, grazing
Class VI – Limitations prevent row crops, used for pasture

13. Land Capability Classes
The eight land capability classes allow for the classification of the land and their end use.
Forests/Wildlife
Class VII – these soils have severe limitations, used for forests and wildlife.
Class VIII – these soils have severe limitations used only for forests and wildlife.

14. Factors that affect Land Capability
There are seven factors that affect the land capability class of a given area.
Each of these factors places limitations on the areas for it’s end use
Slope
Topsoil Thickness
Erosion
Topsoil Texture
Permeability of the Subsoil
Drainage
Effective Depth

15. Factors that affect Land Capability
Slope
The measured amount of rise or fall on a piece of land over a given distance.
Slope is measured over a distance of 25’, 50’ or 100’ and is expressed in percent.
Categories of slope Land Use Category
Nearly Level 0-2% Class I
Very Gentle 2-5% Class II
Gentle 5-8% Class III
Sloping 8-12% Class IV
Strongly Sloping 12-17% Class VI
Steep Over 17% Class VII

16. Factors that affect Land Capability
Topsoil Thickness
is the measured amount of topsoil found on the site. It can be found by measuring down to the color or texture change.
Categories of Topsoil Thickness Land Use
Extremely Thick Over 40” Class III
Very Thick 20 to 40” Class I
Thick 10 to 20” Class I
Moderate 5 to 10” Class I
Thin Less than 5” Class II

17. Factors that affect Land Capability
Erosion
The removal of soil by natural or man made means
Erosion is expressed as a percent of the original topsoil which has eroded.
Original topsoil thickness 12”
Measured topsoil thickness 9”
Eroded topsoil = 3”
3” of eroded topsoil ) 12” of original topsoil = 25% erosion

18. Factors that affect Land Capability
Erosion
Categories of Erosion Land Use
None to Slight – Less than 25% eroded Class I
Moderate – 25 to 75% eroded Class II
Severe – Over 75% eroded Class III

19. Factors that affect Land Capability
Topsoil Texture
Determined by the size of the soil particles in the topsoil.
Fine - smooth and sticky when wet, particles feel fine as flour. When balled in the palm of your hand, it holds the shape and shows finger marks, a long ribbon of soil can be formed by rubbing the soil between the thumb and fore finger.
Medium – medium texture soil is a mixture of sand, silt, and clay particles. It is between fine and coarse. The ball will show some finger marks and hold its shape. A short thick ribbon can be formed.
Coarse – coarse textured soil are made up of mostly sand particles. Sand feels gritty and particles are large enough to be easily seen. The ball breaks in your hand and almost no ribbon can be formed.
All Topsoil Texture class are land use class I.

20. Factors that affect Land Capability
Drainage
Refers to the surface ad internal drainage. The best clue to soil drainage is color.
The color of most subsoils is determined by the amount of iron compound.
When the soil is aerated, the iron reacts with the oxygen giving the soil a yellow or red color. In soils that are not well aerated the soils will have a gray color or mottled with gray.
The more gray mottles found in the soil profile the slower the drainage.

21. Factors that affect Land Capability
Drainage
Categories of Drainage Land Use
Excessively Drained – Course texture, sandy material continues for a depth of 40” Class III
Well-drained – No gray mottles in top 30” Class I
Moderately well-drained – No gray mottles in top 20” Class II
Somewhat poorly drained – No gray mottles in top 10” Class III
Poorly Drained – Gray matrix or gray mottles found in top 10”. Soil may be gray completely to the surface Class IV
Very wet – Surface water remains for extended periods of time Class V

22. Factors that affect Land Capability
Effective Depth
The depth that plant roots can easily penetrate. Usually the combined thickness of the topsoil and subsoil, measured to the parent material.
Categories of Effective Depth Land Use
Deep - Over 40” Class I
Moderate – 20 to 40” Class II
Shallow – 10 to 20” Class III
Very Shallow Less than 10” Class IV