1. Soil & Land resources
Objective: Evaluate soil properties that affect land use in agricultural and urban areas.

2. Classification of Soil
Soil is classified based on its characteristics including…
Texture
Depth
Color
Structure
Consistency
Permeability

3. Soil Texture The proportion of sand, silt, and clay in the soil
Soils are named according to the texture using a soil triangle (AKA textural triangle)
Texture determines how soil can be used and cultural practices that need to be followed to conserve soil
3 classifications of soil texture:
Sandy
Loamy
Clayey

4. Soil Texture: SANDY
Soil cannot be pressed between the fingers to form a ribbon; will not stick to fingers
Feels gritty & rough
Drainage is too fast & has little nutrient holding ability

5. Soil Texture: LOAMY More cohesive than sandy soils
Wide variation in this textural class
Sandy loam- cannot be “leafed out” between fingers, but if done the ribbon will be < ¼” in length
Silt loam- smooth, floury, feel
Pressed into thin, flat ribbons 1/8” thick
Ribbons break off at length of ½”-1.5”
Generally granular, blocky, or massive in structure with friable or firm consistency
Most favorable for root growth, hold most available water for crops and retain fertilizer nutrients

6. Soil Texture: CLAYEY
When wet, these soils form ribbons 1/8” thick at lengths of 1-2 inches
Very cohesive & can be molded into almost any form
Distinct thumb impressions can be made
May be blocky, platy, or massive in structure and generally are firm or very firm in consistence

7. Soil Structure The arrangement of soil particles in shapes and pieces
Importance: Water movement & root development
Water moves faster through granular soil than through blocky soil

8. Soil Structure

9. Soil Structure
Single grain: each individual soil particle stands alone
Granular: aggregates are rounded in form; very desirable
Blocky: particles cling together to form an angular shaped soil
Platy: found where soil has periodically flooded; forms plates or sheets
Massive: has no structure; caused by mismanagement (wet tillage)

10. Soil Consistence
The ease of working with the soil; the resistance a moist volume of soil offers to rupture
Determined by pressing the soil ped between the thumb and extended forefinger
3 Consistence Classes:
Loose: soil offers no resistance to crushing (sandy/single grained)
Friable: soil crumbles with slight pressure (loamy, some clayey)
Firm: soil crumbles only when moderate pressure is exerted

11. Soil Consistence
Consistence classes recognized in the subsurface layer:
Very firm: strongly resists crushing, most red clays
Non-sticky: evaluated when wet; little or no adherence to fingers
Sticky: evaluated when wet; soil clings to one finger, loamy or clayey
Very Sticky: tends to hold the fingers together when soil is pressed between fingers; causes major problems

12. Erosion
Erosion by wind and water lowers the agricultural productivity of soils
The degree of erosion is revealed by examining the top 6 inches of the surface layer
None to slight: All top 6 inches is similar in physical characteristics
Moderate: 25-75% of the top 6 inches is from the subsurface horizon (mixed)
Severe: 75% or more of the original topsoil has been removed

13. Permeability The movement of water in the soil AKA internal drainage
Depends on soil texture & structure
Infiltration: the moving of surface water into the soil
Percolation: the moving of water down through the soil

14. Permeability Rapid- associated with sandy texture
Moderate- associated with loamy texture and blocky or granular structure
Slow- associated with clayey sub-surfaces with blocky structure, firm moist consistence and very firm wet consistence
Very slow- associated with clayey sub-surfaces having massive or platy structure, sometimes with blocky structure

15. Soil Texture Triangle
Use a soil texture triangle to determine what class a soil falls into

16. Soil Depth Varies with thickness of horizons
Generally, deeper A horizon or topsoil equals greater fertility
Generally, depth is considered as:
Very shallow= <10 ft.
Shallow= ft.
Medium= ft.
Deep= >40 ft.

17. Soil Depth
Limiting Layer: layer in soil in a subsurface zone that seriously restricts root and water movement through it
4 Depth Classes:
Very shallow= <12 inches
Shallow= inches
Moderately deep= inches
Deep= >36 inches

18. Slope Think Rise over Run, expressed as a %
Shows the difference in elevation in feet over the horizontal distance in feet between two points
For example, a 4% slope means that the land surface is going up or down at the rate of FOUR feet every 100 feet of distance
A 10% slope would mean that the land climbs or rolls down at the rate of _________ feet per 100 feet

19. Slope There are SIX Slope Classes: 0-2% = Nearly level
2-6% = Gently sloping
6-10% = Sloping
10-15% = Strongly Sloping
15-25% = Steep
25+% = Very Steep

20. Drainage
Internal drainage is important in soils because of its effect on the development of the soil itself and upon its use and management
Internal drainage is related to the level of “ground water” or “water table”
Gray colors within 36 inches of the surface are the primary clues to poor drainage in the soil

21. Drainage Drainage Class Color Depth Well Moderately Well
Shades of red, yellow, or brown
Top 36”
Moderately Well
Gray mottling
24-36”
Somewhat Poorly
Bright colored
Upper 12”
12-24” range
Poorly
Complete profile is gray or dark gray
If the surface horizon is black, it must be <6” thick
Very Poorly
Black surface horizon
>6” thick

22. Drainage Most crops need a moderate to well drained soil
Thus, the color or shade of most topsoil suitable for crops should be ____________________.

23. Soil Color Tends to vary widely Depends on: Parent material
Organic material
Drainage
Texture-at times

24. Surface Water Removal
The rate that water will either run off the surface of the soil or infiltrate into the soil
It is very important in the use and management of soils
Rapid water management across soils can cause erosion and crop drought
Rapid water movement into the soil can indicate conditions favorable for excessive leaching and droughtiness

25. Surface Water Removal
Very slow removal of water is associated with wetness, poor aeration and possible drowning of crops
Slow surface water removal is most favorable and is associated with Class I land
Why would this be a good thing?

26. Evaluation
In evaluating surface water removal, there are two major soil characteristics to consider:
The slope of the soil-Generally, the steeper the slope, the higher the rate of surface water removal
The permeability of both the surface and subsurface layers

27. Surface Water Removal Classes
Rapid
Well drained soils on any slopes, sandy textures in both surface and subsurface layers
Soils with sandy surface layers 20-40” thick
Soils with any surface or subsurface characteristics where slope is greater than 6%
Moderate
Well drained soils with sandy surface layer 20-40” thick on slopes of 0-2%
Soils with sandy or loamy surface on slopes of 4-6%
Soils with clayey surface layers on slopes of 2-6%

28. Surface Water Removal Classes
Slow
Include, most well, moderately well, and somewhat poorly drained soils on 0-4% slope
Moderately well and poorly drained soils having a very slow permeability and 0-2% slope

29. Flooding
It is important to determine if a soil is located in a floodplain or in an area that might be subject to flooding
Can be determined by:
Position on the landscape
Evidence in the soil profiles-layers deposited by floods
Maps available from municipalities
Flood Hazard Classes:
No hazard-not in a floodplain or in an area prone to flooding by surface runoff
Potential hazard-not in a floodplain, but in a depression or low lying area that may be flooded by excessive runoff during heavy rains
In floodplain

30. You are a Soil Scientist
Help determine what type of soil...