Introduction to Soils and Soil Resources

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Introduction to Soils and Soil Resources

• 2001

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Contact the Instructor

• Edith Olson
• 705 General Services Building
• Phone [phone]
• E-mail ecolson_at_ualberta.ca

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Conduct

• No cheating
• No copying
• Academic offense
• Penalties

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Timeline

• So much material, so little time
• Break at 750 resume at 810
• Module one weeks one to four
• Module two weeks five to eight

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Course Objectives

• Terminology
• Characteristics
• Processes
• Soil resources

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Learn About

• Soil formation
• Physical properties of soil
• Chemical properties of soil
• Soil as a home for life
• Affects of human activities on soil

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Course Format

• Lectures
• Assignments
• Labs
• Discussion

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Text Book

• Introduction to soil science and soil resources.
  The pedosphere and its dynamics. A systems
  approach to soil science. Noorallah Juma. 1999

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Lab Manual

• Introduction to soil
• Science and Soil Resources Lab
• Manual (ready soon!)

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Recommended Reading

• The Nature and Properties of Soils. (Any
  edition) Nyle C. Brady and Ray R. Weil.1996

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Recommended Reading

• The Canadian System of Soil Classification.
  Agriculture and Agri-food Canada. 1998.
• Soil Science Principles and Practices. Third
  edition. R. L. Hausenbuiller.1985

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Web Sites

• For soils ERM information go to
• Http//www.soils.rr.ualberta.ca/SoilsERM
• For online access to the textbook go to
• pedosphere.com

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Important Dates in 2001

• Labs Feb 10 and March 10
• Module 1 exam Feb 10
• Module 2 exam March 10
• 9 am to 1 pm or noon to 4 pm

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Exams

• 30 multiple choice questions
• 30 _at_ 2 marks each worth 60
• 3 or 4 questions requiring short answers
• worth 40
• one hour exam
• Dont panic. You can do it!

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Assignment of Marks

• Module exams 2 _at_ 30 60
• Assignments 2 _at_ 5 10
• Assignments 5 _at_ 4 20
• Hands-on labs 2 _at_ 5 10

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Written work

• Use pen or word processing for assignments
• Show all working
• Neat

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Module 1
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Objectives

• The global view of soil
• Fundamental soil properties
• Identifying and describing soil
• Soil distribution in the landscape
• Canadian Soil Classification System
• Legal land survey
• Soil survey and mapping

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Material for Module 1

• Sections 1 to 5 and 12 of the textbook
• Website
• Human Interaction with the Terrestial Surface
• The Soils of Alberta tutorial
• Soils in Specific Canadian Ecozones

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Soil and History

• Civilization is based on the soil
• Destroy the soil, destroy civilization
• Preserve the soil, preserve life

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Uses of Soil

• Engineering
• Agriculture
• Reclamation

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Soil supports life

• Micro and Macro organisms
• Reservoir for nutrients and water
• Protection from temperature
• Gas exchange

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Definition

• Skin of the Earth
• Three phase system Solid, Liquid and Gas
• Natural Body

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Soil

• Made from parent material
• Influenced by climate
• Influenced by relief
• Home to micro and macro organisms
• Changes over time

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Regolith

• Unconsolidated residues resulting from the
  chemical and physical weathering of rocks

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Weathering

• The breakdown of rocks and minerals by chemical
  and physical processes.
• Minerals make rocks - rocks weather back into the
  minerals of which they were made.

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Rate of weathering

• Depends on
• the size and composition of the minerals
• soil pH
• temperature
• biotic activity
• water and air content

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Parent Material

• Unconsolidated material
• The material from which soil is formed
• Weathered chemically and physically

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Soil Components

• Mineral
• Organic
• Water
• Air

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Soil Horizon

• A distinct layer of soil
• Approximately parallel to the surface
• Differs from the layer above and below it

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Master horizons

• A
• B
• C
• O
• LFH

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A horizon

• Mineral
• At or near the surface
• zone of removal of materials in suspension
• zone of removal of materials in solution
• zone of maximum accumulation of organic carbon
• or a combination of these zones

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B horizon

• Mineral
• enrichment of silicate clay, iron,aluminum or
  humus
• prismatic or columnar structure with stains
  associated with exchangeable sodium
• altered by hydrolysis, reduction, or oxidation to
  change structure or colour

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C horizon

• Mineral
• relatively unaffected by pedogenic processes that
  are taking place in the A and B horizons.
• Could be gleyed
• Could have carbonates and soluble salts

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O horizon

• Organic
• More than 17 organic matter
• Found in organic soils
• Common at the surface of wet mineral soils

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LFH

• Organic
• Found under forest vegetation
• May have only L
• Spongy
• Decaying organic forest litter

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Soil Profile

• Two dimensional vertical section of a soil
• Example a road side cutting

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Soil Profile
A horizon
B horizon
C horizon Parent Material

• Rock

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Soil as an Open System

• Soil interacts with the environment around
• and within it to exchange
• water
• gases
• minerals
• energy
• nutrients

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Texture, Structure and Colour
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Soil Texture

• The percentages of sand, silt and clay in a soil.
• Soil assigned to a texture class
• Does not include the organic matter

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Texture Triangle

• Tells us what the soil texture is.
• Determined by percent sand, silt and clay.
• Hand and lab analysis to get texture.

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Particle size ranges
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Texture

• Tells us something about the physical and
  chemical properties of the soil
• Examples
• Clay soil will shrink and swell
• Clay soil and cation exchange
• Sandy soil wont hold water

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Coarse and Fine soil

• A coarse soil has a high percentage of sand
• Gritty feel
• A fine soil has a high percentage of clay
• Smooth feel

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Texture and physical properties

• How much pore space?
• Affects how much air and water the soil can
  hold.
• Arrangement of the particles
• Affects how well the soil packs.
• Implications for plant roots.

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Bulk density

• Bulk density is the proportion of solid in a
  given volume
• Due to aggregation, clay has less solid in a
  given volume than sand
• So clay has more pore space than sand and can
  hold more water or air.

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Texture and chemical properties

• Adsorption
• Surface area
• Clay has more surface area than sand
• More area available for chemical reactions and
  for the adsorption of water

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Structure

• The combination of the primary particles of sand,
  silt and clay into secondary particles such as
  peds, blocks, aggregates and columns.

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Type of Structure

• The type of structure is determined by how
  distinct the arrangement of particles is, the
  size of the arrangement and the shape.

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Types of soil structure

• aggregates
• blocks
• plates
• prisms
• columns
• structureless

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Grade of structure

• How obvious is the structure?
• Very - strong
• Not very - medium
• Hard to see - weak

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Size of structure

• How big is the arrangement of the particles?
• Measure it.
• Use a size chart
• Use a subjective term to describe it such as fine
  or medium or coarse.

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Type of Structure

• The shape
• Platy
• Granular
• Blocky
• Prismatic
• Structureless

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Block like structure
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Block Like Structure
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Block Like Structure
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Plate like structure
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Type Prismlike
Credit CSSC Pedosphere.com
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Type Prismlike
Credit CSSC Pedosphere.com
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Type Prismlike
Credit CSSC Pedosphere.com
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Type Structureless
Credit CSSC Pedosphere.com
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Examples

• Strong, medium, subangular blocky
• Weak, fine, granular
• Medium, coarse, platy
• Single grain
• Massive

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Importance of structure

• Makes the soil porous
• Affects physical,
• chemical and
• biological processes

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Structure and physical processes

• resistance or susceptibility to erosion
• infiltration and runoff
• ability of the soil to conduct water
• drainage and aeration

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Structure and nutrient cycling

• leaching
• ability to weather the soil
• ion exchange
• gas exchange
• mineralization and immobilization

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Structure and carbon cycling

• Root turnover and exudation
• microbial activity and turnover
• decomposition
• respiration
• humification
• accumulation of organic matter

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Bulk density

• Symbol Db or ?b
• bulk density mass of oven dry soil
• volume of soil and pores
• Units are g cm-3 or Mg m-3

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Measuring bulk density

• Oven dry the soil at 105oC
• Record the oven dry weight
• Measure the volume occupied by the soil
• calculate bulk density as
• weight of oven dry soil
• volume of soil

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Particle density

• The density of the particles themselves
• Not the bulk density
• Does not take into consideration the pore space
• Always less than bulk density due to smaller
  volume

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Particle density

• Mass per unit volume of the soil particles
• Symbol Dp or ?p
• particle density mass of particles
• volume of particles
• Units are g cm-3 or Mg m-3

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Particle density

• For calculations, we assume that the particle
  density is
• 2.65 g cm-3
• which is the same as
• 2.65 Mg m-3

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Typical bulk densities
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Pore space

• Bulk density and pore space related
• Pore space expressed as a
• Pore space (1-Db/Dp) x 100
• Pore space also called porosity

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Aggregation

• Aggregates consist of mineral particles and
  organic material which are intimately bound.
• Aggregates also contain air water
• Aggregation of particles reduces bulk density
  because micropores are present within soil
  aggregates.

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Pore space and texture

• Clay soils have smaller pore spaces than sand.
• Clay soils have more pore spaces than sand.
• Clay soils have more total pore space than sand.
• Combination of intra-aggregate and
  inter-aggregate pore space.

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Texture, Db and porosity
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Porosity/Structure
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Porosity and microbes

• Less pore space, less room for microbes
• Harder to move around
• Water limitations
• Compact soil has no room for microbes

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Conclusions

• As clay content increases, pore space increases
  and bulk density decreases due to heterogeneity
  in soil particle size and arrangement.
• As clay content increases, pore space also
  increases, but the size of individual pores
  decreases.

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Conclusions

• Soil structure results in the development of soil
  pores.
• Water, gases, solutes and clay particles move
  through pores.
• Soil structure controls movement of water, ions,
  solutes, clay and anthropogenic compounds.

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Soil Colour

• Hue. The colour
• Colour value. Lightness of a colour.
• Colour chroma. Purity of a colour.

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Munsell

• Tells us the colour of a soil
• Numerical and descriptive
• Gives a hue, value and chroma
• Munsell notation is H V/C

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Munsell Color System

• A color designation system specifying the
  relative degrees of the three simple variables of
  color
• hue dominant spectral color
• value lightness of color
• chroma purity of color
• Red (5R 6/14)

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Colour and soil properties

• Distinguishes soil horizons
• Relates to the soil organic matter
• Relates to the minerals
• Relates to the moisture regime
• Need to know if soil was dry, moist or wet when
  the colour was assigned

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Soil Color

• Used to distinguish soil horizons
• Mineral and organic components impact color to
  soil
• Colloidal materials impact soil color
• Humus is black
• Iron oxides are red
• Reduced iron is blue green

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Soil Color

• Soil color reflects regime of water and air in
  soil.
• Reduced soils have soluble iron and manganese
  compounds
• Oxidized soils have iron and manganese oxides
• Example of iron nail

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Soil Color

• Soil color in surface horizons is correlated with
  organic matter content nutrient supplying power
• Quartz imparts light color
• Feldspars are predominantly red
• Soil color needs to be used with soil texture and
  structure

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Conclusions for Soil Color

• Soil color can be described qualitatively and
  quantitatively under specified moisture
  conditions.
• Soil color indicates regime of water and air in
  soil.
• Soil color in surface horizons is correlated to
  soil organic matter content.

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Next week

• Review week 1.
• Relationship of climate to vegetation in Alberta
• Types of Parent materials found in Alberta

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Are you still awake??