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What is Soil?. Conceptual Aspects: Habitat Micro-organisms Bacteria, Fungi – both good and bad Viruses Macro-organisms Worms, Arthropods, Detrivores and Predators Plants Small Mammals Birds. What is Soil?. Conceptual Aspects: Provider to plant life Rooting substrate

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What is Soil?

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What is soil

What is Soil?

  • Conceptual Aspects:

    • Habitat

      • Micro-organisms

        • Bacteria, Fungi – both good and bad

        • Viruses

      • Macro-organisms

        • Worms, Arthropods, Detrivores and Predators

      • Plants

      • Small Mammals

      • Birds

What is soil1

What is Soil?

  • Conceptual Aspects:

    • Provider to plant life

      • Rooting substrate

      • Water holding and release

      • Nutrient supply and reserve

      • Heat sink and release

      • Soil gases

      • Symbionts

        • Bacterial and fungal

        • Insects

What is soil2

What is Soil?

  • Physical Aspects:

    • Minerals (from rocks)

      • Sand

      • Silt

      • Clay and Colloids

    • Organic Matter

      • Plants and Roots

      • Detritus (decaying organic matter)

      • Animal waste (including microbes)

    • Pore Space

      • Air

      • Water

What is soil3

What is Soil?

  • Carbon Sink

    • Water filter

  • Indicator of ecosystem health

What is soil4

What is Soil?

We need to keep all these things in mind in our management practices

How does this change how we treat the soil?

What is soil5

What is Soil?

  • Habitat

    • What happens when we disturb this habitat?

      • At micro and macro level?

    • What happens when we make additions to, or removals from, this habitat?

      • Carbon:Nitrogen ratio?

      • How do soil organisms and plants respond?

      • Nutrient loss or gain?

  • Providing for plant life

    • What are the short-term and long-term results?

    • Are we providing for the soil as well as the plants?

      • What is the difference?

What is soil6

What is Soil?

  • As a habitat we need to treat soil like a living organism, which requires:

    • Food

    • Water

    • Air

    • Shelter

      • Cover crops

      • Mulch

        • Living

        • Dead

        • Snow

    • Tender loving care…

Short commercial break

Short commercial break

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Physical attributes of soil

Physical Attributes of Soil

  • Mineral Components

    • Sand

    • Silt

    • Clay

Physical attributes of soil1

Physical Attributes of Soil

  • Sand

    • Largest soil mineral particles (.02 – 2 mm)

    • Formed greatly from physical processes

    • Spherical/erratic in shape

      • Sand = little rocks

    • Larger pore spaces

      • Good drainage

    • Does not hold a charge

    • Difficult to compact

Physical attributes of soil2

Physical Attributes of Soil

  • Silt

    • Size between sand and clay (.002 - .02 mm)

    • Usually physically formed out of sand

    • Hold and releases water well

    • Flat or round in shape

    • Holds very little charge

    • Feels soapy

    • Carried in moving water

Physical attributes of soil3

Physical Attributes of Soil

  • Clay

    • Smallest soil mineral particle (< .002 mm)

    • Holds water very well

    • Holds strong negative charge for mineral adsorption

    • Susceptible to compaction

    • Platy-/flat-shaped particles

    • Various lattice structures

Physical attributes of soil4

Physical Attributes of Soil

  • Clay

    • Understanding structure of clay is important for:

      • Compaction

      • Water holding

      • Cation adsorption

      • Soil cultivation

  • Clays are categorized by their layer structure

    • Relationship of Si-tetrahedral and Al-octahedral sheets

    • 2:1; 1:1; 4:1; 5:2

Physical attributes of soil5

Physical Attributes of Soil

2:1 Clay

  • Shrink and swell

    1:1 Clay

    No change

Physical attributes of soil6

Physical Attributes of Soil

  • Shrink and Swell of Clay

    • Interlayer space expandswith increasing watercontent in soil

    • Space contracts as wateris removed

    • Clay can crack when it shrinks

Physical attributes of soil7

Physical Attributes of Soil

  • Mineral ratios determine soil texture

Physical attributes of soil8

Physical Attributes of Soil

  • Attributes of Different Soil Textures

Physical attributes of soil9

Physical Attributes of Soil

  • Why is Texture Important?

    • Water Infiltration

    • Water Storage

    • Fertility

    • Aeration

    • Trafficability

  • Soil texture knowledge is the key to developing an overall soil maintenance and improvement plan

And now a short break

And now a short break…

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Organic matter

Organic Matter

  • Soil organic materials are made up of:

    • Dead and decaying plants or animals

    • Animal manures

    • Microbial by products

  • Materials decomposed to different stages exist simultaneously

  • Manure and compost are common OM additions to soil

Organic matter1

Organic Matter

  • Organic matter’s role in soil:

    • Holds soil particles together; stabilizes soil

      • Reduces erosion risk

    • Increases soil’s water holding and transmitting ability

    • Stores and supplies nutrients to plants and microbes

    • Minimizes soil compaction

    • Carbon sink

    • Ameliorates the effect of environmental pollutants

      • Immobilizes them; reduces leaching

  • Usually 5-8% of soil; 30% or more in org. soils

Organic matter2

Organic Matter

  • Soil Organic Matter Characteristics

    • High Cation Exchange Capacity (CEC)

    • High in Carbon (C)

    • C:N ratio- indicator of Nitrogen (N) availability to plants

    • Nutrient concentration and ratios variable

    • Particle density: 900-1300 kg/m3

    • Bulk density: 180-200 kg/m3 (peat) or 130 kg/m3 (forest)

    • Holds water better than mineral soils

Organic matter3

Organic Matter

  • Two Types of Organic Matter

  • Non-humic

    • Primary components from fresh animal and plant waste

    • Easily decomposed by microbes (when present)

    • Comprise 20-30% of Soil OM

    • Decompose to:

      • Carbohydrates (several types)

      • Amino Acids

      • Lipids

      • Lignin

        • Very resistant to decay

      • Other compounds

Organic matter4

Organic Matter

  • Two Types of Organic Matter

  • Humic

    • Biochemical decomposition of non-humic materials

    • Resistant to further decomposition

    • Accumulate in soil

    • Dark in colour – give soil dark characteristic

    • 60-80% of soil OM

    • 3 types:

      • Humins: larger particles; low number of carboxyl groups; inactive.

      • Humic acids: smaller than humins (approximately colloid-sized); more carboxyl groups than humins.

      • Fulvic acids: smallest humic substances; large number of carboxyl groups;  most active among humic substances.

Organic matter5

Organic Matter

Organic matter6

Organic Matter

  • Carboxyl and Hydroxyl Groups

Organic matter7

Organic Matter

Living Material

Dies onto soil



This process is driven by biological decomposition – mostly from soil bacteria and fungi

Organic matter and texture

Organic Matter and Texture

  • What role does OM play in texture?

And another break

And another break…

Click me, damnit

Soil colloids

Soil Colloids

  • Soil Colloids

    • Microscopic soil particles (w/electron microscope)

    • Made up mostly of clays and organic materials

    • Very large surface area

    • Carry many exchange sites/charges

      • Mostly negative except in acid soils

      • Hold soil cations (positively charged)

    • Holds water to cations

    • Major contributor to soil nutrient holding capacity

Soil colloids1

Soil Colloids

  • There might be a diagram here someday…

And now another break

And now another break

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Soil formation

Soil Formation

Where does the mineral component come from?

From the weathering of rocks.

Rocks are made up of minerals

Soil formation1

Soil Formation

  • Primary Minerals  Sand and Silt

    • Formed at high T and P (at depth); anaerobic conditions

    • Physically and chemically formed

  • Secondary Minerals  Clay

    • Come from primary minerals

    • Formed at low T and P (at surface) with Oxygen present

    • Mostly chemically formed

Soil formation2

Soil Formation

Weathering of Rocks


Chemical 1

Chemical 2

(note: base-forming cations)

Chemical 3


Five soil formation factors

Five Soil Formation Factors

Parent Material





Gleysol soil

Gleysol Soil

Tiny little Video here

Not another one

Not another one…

You know what to do

Five soil formation factors1

Five Soil Formation Factors

Parent Material

  • Residual

    • In situ; long periods of weathering

  • Cumulose

    • Due to plant life and anaerobic conditions

      • High water table

    • Peat and muck soils

  • Transported

    • Gravity - Colluvium

    • Wind - Eolian

    • Water - Alluvium

    • Ice - Glacial

Five soil formation factors2

Five Soil Formation Factors

  • Climate

    • Temperature and rainfall are major factors

      • Affect intensity of weathering

    • Increased T and precipitation accelerate weathering

  • Biota

    • Plants influence organic matter

    • Arthropods and worms mix soil; add to OM

    • Small mammals also mix soil

Five soil formation factors3

Five Soil Formation Factors

  • Topography

    • Slope influences soil development

      • Water infiltration rate

      • Surface runoff

      • Vegetation

    • Aspect

      • North and South slopes develop differently

    • Elevation

      • Climate changes with altitude

Five soil formation factors4

Five Soil Formation Factors

  • Time

    • Often noted as most important soil formation factor

    • Our soils in Lower Mainland are relatively young

      • Since last ice age 10,000 years ago

Five soil formation factors5

Five Soil Formation Factors

Great Soil Formation Videos Here

Soil formation processes

Soil Formation Processes

  • Additions

  • Losses

  • Transformations

  • Translocations

Podzol soil

Podzol Soil

Video here

Soil horizons

Soil Horizons

Soil horizons1

Soil Horizons

  • Organic (O) Horizon

    • High in organic residue from plant drop

  • A Horizon

    • Mineral component mixed with OM

    • Most fertile part of soil; location of much root activity

    • Exhibits Eluviation in soil solution

  • B Horizon

    • Subsoil

    • Exhibits Illuviation of clay, OM, oxides

  • C Horizon

    • Little influence by soil-forming processes

Soil horizons2

Soil Horizons

  • Water (W) Horizon

    • Due to high water table

    • Found in Gleysols

  • Bedrock

    • Underlying consolidated material (solid rock)

  • LFH Horizons

    • Usually found in forest soils with high surface residue

And now another break1

And now another break

Click Me

Soil structure

Soil Structure

  • Soil Structure: How the soil fits together

    • Primary particles are arranged into secondary particles called aggregates (or peds)

Soil structure1

Soil Structure

  • Why is Structure Important?

    • Pore space

      • Air and water movement

      • Rooting space

    • Nutrient storage and release

    • Contributes to soil resilience

      • Cultivation

    • Erosion resistance

Soil structure2

Soil Structure

  • How does aggregate formation occur?

    Flocculation + Cementation = Aggregation

  • Flocculation:

    • Primary pulled close together (into flocs) by attractive forces (electrostatic forces, H bonding)

  • Cementation

    • Primary particles held together by cementing agents

      • Carbonates; clays; OM; Oxides

Soil structure3

Soil Structure

Soil structure4

Soil Structure

  • Soil Aggregates are classified by their shape

Soil structure5

Soil Structure

  • Spheroidal

    • Typical in A Horizon

    • Rounded; loose

    • Granular (porous) or Crumb (very porous)

    • Greatly affected by soil management/mismanagement

    • Improved with OM additions

Soil structure6

Soil Structure

  • Soil structure is particularly important in providing adequate pore space for:

    • Root growth

    • Water movement

    • Gas exchange

    • Microbial activity

    • Macrobial activity

Soil consistency

Soil Consistency

  • Related to texture

  • Very important when considering soil cultivation

  • Dependant on

    • Texture/clay content

    • Clay type

    • Soil water content

Soil consistency1

Soil Consistency

Soil consistency2

Soil Consistency

  • Cultivating soil when too dry

    • Breaks aggregates into small pieces

      • De-aggregates

      • Can result in dust

    • Very damaging to soil structure

    • The drier the soil – the more it acts like powder

Soil consistency3

Soil Consistency

  • Cultivating soil when too wet

    • Where to start?!

  • Compaction

    • Risk and depth of compaction increases in wet soil

Soil consistency4

Soil Consistency

  • Cultivating soil when too wet

  • The wetter the soil - the more it acts like water

Soil consistency5

Soil Consistency

Soil particle and bulk density

Soil Particle and Bulk Density

  • Particle density: Density of individual particles

  • Density = Mass/Volume (M/V)

    ρparticle = Msolids/Vsolids

  • Some particle densities:

    • Water: 1000 kg/m3

    • Organic Matter: 900-1300 kg/m3

    • Minerals: 2650 kg/m3

Soil particle and bulk density1

Soil Particle and Bulk Density

  • Bulk density: Density of particles and pore space

    ρbulk = Msolids/Vsoil

  • Some bulk densities:

    • Mineral or organic soil: 1300 kg/m3

    • Clay Soil: 1100 - 1300 kg/m3

    • Sandy Soil: 1500 – 1700 kg/m3

Soil particle and bulk density2

Soil Particle and Bulk Density

  • Measuring Particle Density:

  • Weight out a dry sample of particle type (e.g., sand)

    • This is your Mass value

  • Fill graduated cylinder with water

    • Record exact water level

  • Drop particles into cylinder of water

    • Record new water level

  • New Reading – Old Reading = Volume

  • Mass/Volume = Particle Density

Soil particle and bulk density3

Soil Particle and Bulk Density

  • Measuring Bulk Density:

  • Collect known sample (Volume) size of soil

    • Use soil core; Volume = πr2h

  • Weigh sample then dry in oven

    • Removes water from sample

  • Weigh dried sample

    • This is your soil Mass

  • Mass/Volume = Bulk Density

Soil particle and bulk density4

Soil Particle and Bulk Density

  • Why is density important?

  • Particle density: not as important as bulk density

  • Bulk density is indicator of pore space

    • Changes in bulk density = changes in pore space

Soil air and water pore space

Soil Air and Water (Pore Space)

Soil air and water pore space1

Soil Air and Water (Pore Space)

  • Soil Water

Soil air and water pore space2

Soil Air and Water (Pore Space)

  • For future lecture…

What is soil

  • Agricultural Capability Classes

  • Class 1

    • Class 1 land is capable of producing the very widest range of crops. Soil and climate conditions are optimum, resulting in easy management.

  • Class 2

    • Class 2 land is capable of producing a wide range of crops. Minor restrictions of soil or climate may reduce capability but pose no major difficulties in management.

  • Class 3

    • Class 3 land is capable of producing a fairly wide range of crops under good management practices. Soil and/or climate limitations are somewhat restrictive.

  • Class 4

    • Class 4 land is capable of a restricted range of crops. Soil and climate conditions require special management considerations.

  • Class 5

    • Class 5 land is capable of production of cultivated perennial forage crops and specially adapted crops. Soil and/or climate conditions severely limit capability.

  • Class 6

    • Class 6 land is important in its natural state as grazing land. These lands cannot be cultivated due to soil and/or climate limitations.

  • Class 7

    • Class 7 land has no capability for soil bound agriculture.

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