1. MLRA Soil Survey Leader
Basic Soils Training
Soil Morphology
Nathan Jones
MLRA Soil Survey Leader
Andy Oxford
Soil Scientist
January 2013

2. Objectives Soil Horizons Soil Color Soil Texture Soil Structure
Soil Rupture Resistance
Soil Roots and Pores
Soil Restrictive Layers
Soil Boundaries
Soil pH

3. SOIL MORPHOLOGY - a definition
Characteristics and properties of the soil observable in the field within the various soil horizons
The description of the kind and arrangement of soil horizons

4. Soil Horizons Ap Bt Bk Hetland Soil C
We cannot describe or determine the properties of a horizon without first understanding what a soil horizon is.
Hetland Soil C

5. Soil Horizons
“Horizon”: A layer of soil or soil material approximately parallel to the land surface and differing from adjacent related layers in physical, chemical, and biological properties or characteristics such as color, structure, texture, consistence, or pH
“Profile”: sequence of horizons stacked vertically that tells the story of how the soil formed
“Series”: name given to profile that has characteristic set of properties and horizons (determined by NRCS)

6. Soil Sampling Units Houdek Series
Purpose of this slide is to show how a pedon and its horizons can represent the landscape. Additionally, how the defined sequence of horizons with given properties represents a soil series. Finally, how both the soil series and landscape are used to create a map unit and ultimately a soil map. A soil map shows the location of a soil series on the landscape.
Houdek Series

7. Soil Horizon Development
A-Horizon development
Accumulation of organic matter
Clumping of individual soil particles
Distinct from parent material and other layers
B and C horizon development
Carbonic and organic acids are carried by water into soil where they dissolve various minerals (transformations)
Clay films - thin layers of oriented trans-located clay
Salts and carbonates are carried by water and precipitate in the soil from upper to lower horizons (translocation)
Wetting and drying cracks soils and creates soil structure
Weathering of parent material

8. Master Horizons
O = The layer of organic matter on the surface of a mineral soil
A = Topsoil. The mineral soil horizon on the surface with organic matter and low clay
E = The horizon of maximum leaching. Not in all soils, but if present, is located just below the “A” horizon
B = Subsoil. Horizon most often located below A horizon. The zone of maximum clay accumulation
C = Weathered rock. Lies below the “A” and/or “B” horizons and has NOT been acted upon by the soil forming processes
R = The hard, consolidated rock beneath the soil
Definition of Master horizons
A horizon – usually has the highest organic matter and fertility.
E horizon – if present, has a whitish color when dry, if wetted, whitish color disappear. Typically in concave landforms e.g. potholes
B horizon –
C horizon –
R horizon -

9. O: litter, forest floor; Oi common, ½-1" thick;
Oa,Oe usually very thin or absent
A: topmost mineral soil; 2-12" typical;
use “p” if abrupt boundary (tillage mark)
E: often absent due to erosion; may be light-colored,
usually same texture as A; not blocky
Transition: usually only one– BE or EB; B often first,
since more distinct
B: usually clayey, blocky, Fe coloration; 6-36" thick;
may be subdivided (B1,B2); use t, w, or h–
only one type per profile
Transition: usually BC (B more distinct)
C: weathered parent material; lower clay,
massive/rock structure; if clear rock-like structure
and appreciable rock fragments, use r (“Cr”)
R: hard rock (cannot be dug); describe type if possible
Skip the illustration. Maybe mention it is just another representation of the master horizons and includes other terms used to describe those layers, but do not discuss any of those terms. Main purpose is to show there are other letters (suffixes) used to describe horizons. Maybe mention a few of them, but do not discuss what they mean. Other purpose is to show there can be transitional horizons, generally between B and C horizons and E and B horizons.

10. Houdek soil series (SD State Soil)Bt Bk
Group exercise #1: Allow volunteers from audience to separate and designate the horizons. Bring in Horizons one at a time. C

11. Soil Horizon Designations
Tonka Soil A E
Group exercise #2: Allow volunteers from audience to separate and designate the horizons. Bring in Horizons one at a time. B C

12. Barnes Soil A B Bk
Group exercise #3: Allow volunteers from audience to separate and designate the horizons. All horizons come in at one time. C

13. Soil Properties
Physical: particle size/arrangement; porosity Chemical: effect on plant growth Biological: determine long-term behavior (“sustainability”)
Transition to soil properties observable within the soil horizons by showing and explaining the different categories of soil properties. Soil properties make up the bulk of soil morphology.

14. Physical Soil Properties
Color
Texture
Structure
Consistency
Roots and Pores
Restrictive Layers
Another transition slide listing the physical soil properties that will be discussed in this training.

15. Soil Color
McIntosh Soil

16. Soil Color Probably the most obvious soil feature
Munsell system color charts used to standardize colors
Hue = the dominant spectral color (related to wavelength of light)
Value = measure of degree of lightness or darkness (amount of light reflected)

17. More Soil Color
Chroma = measure of purity or strength of spectral color
Dominant (matrix) color = the color that occupies the greatest volume
Mottling refers to repetitive color changes that cannot be associated to a soil property. Redoximorphic (redox) features are a type of mottling associated with wetness

18. Soil Color: Pigments in Soils
Dark brown to black: humus/organic matter gives soil this color; topsoils (A horizon)
Reds and yellows: iron oxide, subsoil horizons (B horizons) either red, yellow, oxidized (Fe+3) iron well-oxidized (well-drained)
Grey: reduced (Fe+2) iron; water doesn't drain out, poor drainage; Fe is reduced, depleted
Whitish or light grey: leached out horizons; other pigments (humus, iron oxides) have been leached away
 Munsell system: soil colors matched to color chips in book–
standardized way to describe soil color

19. Munsell color chart: “10YR 5/3” hue value chroma

20. Soil Color Dark brown to black-
Waubay Soil
Dark brown to black-
( A horizon) top soils, humus- decomposed organic material. A few percent of humus gives a brownish color and up to 5% the soil becomes black.
Examples of the soil pigments described earlier.

21. Soil Color Reds and Yellows-
Alabama State Soil
Reds and Yellows-
(B horizons) iron oxide formed during weathering,
Fe+3 is well oxidized (well-drained)
Examples of the soil pigments described earlier.

22. Soil Color Grey colors are caused by reduced Iron (Fe+2 )
Tonka Soil
Grey colors are caused by reduced Iron (Fe+2 )
Water has excluded oxygen from diffusion into soil
Other pigments are leached out from horizons (humus, iron oxides)
Examples of the soil pigments described earlier.

23. Redoximorphic Features
Redoximorphic (oxidation/reduction) Features
Indication that soil is saturated for
some time during the year
Redox depletions (reduction)
low chroma
Fe and Mn have been stripped
from soil
Redox concentrations (oxidation)
high chroma
Accumulation of Fe and Mn
oxides
Point out the depletions and oxidations on the photo.

24. Soil Morphology Exercise 1
Color soil samples with a Munsell color book

25. Soil Texture

26. Soil Texture
Definition (USDA ) - the weight proportion of the soil separates less than 2.0 mm in size (sand, silt, and clay). Or, more commonly, the relative proportions of sand, silt, and clay
Sand = 2.0 to 0.05mm
Silt = 0.05 to 0.002mm
Clay = < 0.002mm
Sand, silt, and clay in various proportions make up 12 textural classes

27. If you have it, bring out the basketball, tennis ball, and needle to illustrate the relative sizes of sand, silt, and clay.

28. USDA Textural Triangle

29. USDA Textural Triangle Example
35 % sand
55 % silt
10 % clay
Texture is ‘silt loam’
Sand mm
Silt to .05 mm
Clay < .002 mm
Textural Class
The percentage of sand sized particles
+ % of silt sized particles
+ % of clay sized particles
Example of how to use the Textural Triangle. Provide another example and have the audience determine the texture.

30. Coarse Fragments
Mineral particles larger than 2.0 mm = rock fragments (gravels, stones, or boulders)
Modifiers = %, %, %, 60-90%, > 90%
Soil texture refers to the sizes of the mineral soil particles and is modified as well as the amount and type of organic matter in a soil horizon. Soil texture is made up of a “textural class” and any “modifier” that is appropriate. The total of the mineral soil particles less than 2 mm are collectively referred to as the “fine earth fraction”. This fine earth fraction is what we use to determine the textural class. The mineral soil particles greater than 2 mm are referred to as coarse fragments. These are used to give the textural class a modifier. Can anyone give me an example of a soil textural class? If that 15 % or more of that SiL were gravels, the textural class would get a modifier of “gravely sil”.

31. Coarse Fragments
Gravels: 2.0 to 75 mm
Cobbles: 76 to 250 mm

32. Coarse Fragments
Stoney: 250 to 600mm
Boulders: 600mm+

33. TEXTURAL CLASSES BY “FEEL” METHOD
Texture by feel method chart.

34. Soil Morphology Exercise 2
Texture by “feel” method

35. Soil Structure

36. Soil Structure - a definition
The aggregation of primary particles into secondary units surrounded by planes of weakness.
Granular
Blocky
Platy
Prismatic
Columnar
Massive
wetting and drying
freezing and thawing
root action
animal activity
organic matter
kind of clay
Initial material
Ped face
Pores
Porosity 30 to 60 % of ped volume
If soil texture is the plywood, 2 X 6 ‘s, and nails that can be packed on a truck, soil structure is the building put together using the plywood, 2 X 6 ‘s, and nails.
Structure creates porosity and surfaces for chemical and physical process

37. Soil Structure - Shapes
Granular - peds are approximately spherical or polyhedral and are bounded by curved or irregular faces (A horizons)
Platy - the peds are flat and “platelike”; they are usually oriented horizontally (E horizons)
Blocky - somewhat “blocklike”; bounded by flat or slightly rounded surfaces; nearly equidimensional (Upper B horizons)
Prismatic - peds are longer than they are wide (Lower B horizons)
Massive – no structural units; material is a coherent mass (C horizons)
Single grain – no structural units; entirely noncoherent; example is loose sand (C horizons)

38. Soil Structure - Shapes
Granular - peds are approximately spherical or polyhedral and are bounded by curved or irregular faces (A horizons)
Platy - the peds are flat and
“platelike”; They are usually
oriented horizontally (E
horizons)

39. Soil Structure - Shapes
Blocky - Somewhat “block like”. Bounded by flat or slightly rounded surfaces; Nearly equidimensional (Upper B horizons)
Angular Blocky Subangular blocky
Prismatic - Peds are longer than they are wide (Lower B horizons)

40. Soil Structure - Shapes
Columnar – Similar to prismatic; vertically elongated units with rounded tops; found in natric horizons

41. Soil Structure Affects: Pore space Liquid and gas movement
Permeability
Structure is strongly correlated to many
properties, particularly soil hydrology

42. Soil Morphology Exercise 3
Observe structure types using the structure kits

43. Soil Rupture Resistance

44. Soil Rupture Resistance - a definition
The resistance of soil to deformation or rupture; or the degree of cohesion (tendency of similar surfaces to cling to one another) or adhesion (tendency of dissimilar surfaces to cling to one another) of the soil mass

45. Soil Rupture Resistance - Moist Soil
loose
very friable
friable
firm
very firm
extremely firm

46. Soil Rupture Resistance
Loose: You have trouble picking out a single ped and the structure falls apart before you handle it.*
Friable: The ped breaks with a small amount of pressure.
Very Friable
* Soils with “single grained” structure always have loose consistence.
Firm: The ped breaks when you apply a good amount of pressure and dents your fingers before it breaks.
Extremely Firm: The ped can’t be crushed with your fingers (you need a hammer!).
Very Firm

47. Soil Morphology Exercise 4
Practice determining moist rupture resistance class

48. Soil Roots and Pores

49. Soil Roots and Pores
Describe the quantity, size, and location of roots and pores
Provides a visual representation of soil health
Affected by soil structure
Impacted by soil restrictive layers and management and use

50. Soil Roots and Pores

51. Soil Restrictive Layers
Soil material
Shale bedrock

52. Soil and Root Restrictive Layers
Bedrock
Natric horizons
Sand and gravel
Clay pan
Water
Compaction

53. Soil Restrictive Layers
Influences:
Rooting depth
Water infiltration
Salt accumulation
Land use and management

54. Soil Boundaries

55. Soil Boundaries - a definition
A surface or transitional layer between two adjoining horizons or layers
Most boundaries are zones of transition rather than sharp lines of division

56. Soil Boundaries - Distinctness
Abrupt = less than 1 inch thick
Clear = 1 to 2.5 inches thick
Gradual = 2.5 to 5 inches thick
Diffuse = greater than 5 inches thick

57. Soil Boundaries - Topography
Smooth = the boundary is a plane with few or no irregularities
Wavy = there are undulations in which depressions are wider than they are deep
Irregular = pockets that are deeper than they are wide
Broken = One or both of the horizons separated by the boundary are discontinuous and the boundary is interrupted

58. Soil Boundaries
Describe the boundaries in these pictures.

59. Soil Chemical Properties
Acidity/alkalinity: “pH”
Affects many other soil chemical properties
Large effect on nutrient availability (solubility)
Optimum range (most plants):

60. Soil pH

61. Soil pH – definition
A numeric designation of the acidity or alkalinity in soils
A measure of the H+ ion activity in soils
On a scale of 0 to 14

62. Soil pH - classes Very strongly acid: 4.5 to 5.0
Moderately Acid: 5.6 to 6.0
Slightly Acid: 6.1 to 6.5
Neutral: 6.6 to 7.3
Slightly Alkaline: 7.4 to 7.8
Moderately Alkaline: 7.9 to 8.4

63. Soil pH
pH influences nutrient availability, rate of biological and chemical processes, the amount and types of plants and microorganisms present, and the corrosion potential of concrete or steel structures in the soil
You can alter the soil pH by incorporating compounds in to the soil. The most common is to add lime (calcium carbonate, CaCO3 ) to increase the pH

64. Soil pH-nutrient availability

65. Questions??

66. Credits Pictures and Content from PowerPoint Presentations Created by:
William Miller and David Radcliffe, Crop and Soil Sciences, University of Georgia
University of Florida Soil Lab
Alabama A&M University
USDA Natural Resources Conservation Service Alaska Soil Survey Program
Earl D. Lockridge, USDA NRCS National Soil Survey Center

67. Credits Other pictures and content provided by:
USDA Handbook No. 18, Soil Survey Manual by the Soil Survey Division Staff
Field Book for Describing and Sampling Soils Version 2.0 by USDA NRCS National Soil Survey Center
USDA NRCS Keys to Soil Taxonomy 10th Edition
Verdegaalbrothers.com
Stthomas.edu
Soilquality.org
Noonturfcare.com
Viette.com
Ehow.com
Gardeningstepbystep.com
Mccc.msu.edu
Deeproot.com
Swac.umn.edu
Scifaithkansas.net
Allianceforwaterefficiency.org
Ecoclublive.blogspot.com
Sd.nrcs.usda.gov
Water-research.net