Ren R 210 - Module 1 exam

Vasily Dokuchaev (1846-1903)

First person to define soil as a living being and as something different from dirt

F.A Wyatt

Albertan soil scientist who created the Breton plots, plots studying the effects of converting forest plots into agriculture plots)

What are the qualifying factors of soil?

• Unconsolidated geologic, or organic, material (meaning there is airspace and it isn’t just rock)

• Has a minimum depth of 10 cm

• It’s affected by soil forming factors and processes (things that create soil are affected by soil)

• It’s capable of supporting plant growth

What isn’t soil?

• Material that has been displaced unnaturally (Eg: A dumptruck dumps a pile of dirt somewhere is an unnatural displacement)

• Bedrock

• Anything less than 10 cm deep

• Sediment covered in more than 60 cm (approx 2 feet) of water

Soil is made up by material that meets specific dimensions, and is a three dimensional body

• Mineral = Rocks, Calcium, Carbonates, Sodium, etc

• Organic material = Roots, dead plant materials, microbes

• Good soil is 50% water and air (these are the homes for the microbes)

Two concepts of soil:

• Pedology: The study of soils in relation to their environment (how they were formed, what it is)

• Edaphology: The study of soils as a medium for plant growth (studying the chemical and biological interactions in soil)

Pedology is an integrative science that happens at the intersection of

• Atmosphere

• Biosphere (animals and plants, roots and leaves, dead organic matter all interact with soil)

• Hydrosphere (Water moves through the soil)

• Lithosphere (Outer most shell of the Earth, with soil on and in it)

Soil science integrates

• Surficial geology/geomorphology: Studying the surface of the Earth, what happened to cause the surface to look like that, and the original conditions that created soil

• Mineralogy of primary and secondary minerals: soil fertility comes from the minerals freed as rocks are broken down

• Hydrologic cycles, physics of water: The movement of water and soil, and how soil drains water

• Applied Sciences (Inorganic/organic chemistry, microbiology, plant biology, ecology)

Pedon

• The smallest volume that can be regarded as soil; the basic unit of soil and the fundamental building block of soil

  • 1 m³

Polypedon

A group of similar pedons who share the same biological, physical, and chemical properties

A group of similar pedons who share the same biological, physical, and chemical properties

The 2 dimensional vertical slice through the soil, classified based on its horizon

Solum

The horizons with active soil processes

2 broadways to categorize soil:

• What’s the parent material?

• How quickly did it meet soil criteria? (affected by environmental factors)

2 main types of rock from glaciers

Igneous rock and sedimentary rock

Igneous rock

• Made from cooled magma, and resisted glacial retreat/disturbance. Mostly left behind as gravel and sand

  • Results in more acidic soil (3.5 to 5) with fewer base cations

  • Best for trees 

  • Eg: Canadian Shield

Sedimentary rock

• Soft rock that was easily pulverized by glacier retreat, made from eroded materials. Largely left behind as gravel and clay

  • Abundant base cations result in a higher pH in the soil (5-8.5), making very fertile soil

Eg: Prairies, coast, mountains

Base cations

Ca²⁺, Mg2+, P2+, and Na2+ that lead to fertile soil and contribute to how well plants grow

Organic soil

Soil made from organic plant material (eg: peat)

Residual soil:

Formed in place

Transported and the 2 types

• Moved from its original spot

  • Sorted: Homogeneous particle size (particles are all roughly the same size)

  • Unsorted: Heterogenous particle size (random, and highly variable soil sizes)

4 Modes of transportation:

Water, Wind, Ice, Gravity

Sorted soil is cause by what forms of transportation

• Water: High energy, resulting in picking up the heavy things first, sorting things from largest to smallest

• Wind: Low energy, resulting in things sorting smallest to largest

Unsorted soil is caused by what types of transportation

Gravity (pulls everything down, regardless of size) and Ice (stays in place when ice melts)

Main types of Transportation

Till/moraine

Glaviofluvial

Glaciolacustrine

Till AKA moraine

Sediment comes directly from retreating glacier, resulting in unsorted particles and an undulating landscape

Glaciofluvial AKA rivers

Melting water creates channels in Glacier and carries sediment, resulting in well sorted material and an undulating or flat landscape

Glaciolacustrine AKA lakes

• Flat surface areas that end up as Glacier lakes with low flow water, resulting in well sorted particles and a flat landscape)

  • Main one in Edmonton

  • Leads to the most fertile soil

Modes of deposition

• Fluvial: Moving water (rivers created from Glacier retreats)

• Lacustrine: Standing water (lakes created from glacier retreats)

• Marine: Tides (moves sediment in and out of islands)

• Eolian: Winds that transport loess (silty mantel)

• Glacial: moraine, till

• Colluvium: Gravity, rock being pulled down because of gravity (eg: land slide)

Varves

The stratification caused by the seasonal deposition of sediment in water

Key soil characteristics tell us how soil functions, what are they?

• Colour: brown, green/blue, red/yellow (iron), white (carbonates)

• Texture: Sand, silt, and clay mixture. Different size classes give information on water movement, plant growth, and nutrient retention

• Structure: How it’s clumping, the distinctive patterns caused by the texture particles form

• Presences of carbonates: Determines the pH, fertility, etc

Soil colour is described based on

• Hue: The dominant spectral colour (usually between red and yellow in Alberta)

• Value: Degree of darkness (with 0 being black, and 10 being white) with lightest at the top, and darkest at the bottom

• Chroma: Intensity of colour (0 being pastel, and 10 being bright) with left being the most intense, and right being the least intense

How does moisture content affect colour?

• As moisture content increases, value decreases (the soil gets darker) because of how water refracts light

  • When water gets mixed into soil it can cause confusion about what the true colour of the soil is, so it’s best to always use dry soil

How does organic matter affect soil colour?

• As OM increases, value decreases and the soil gets darker

  • Light brown - Value >6 - 1-3% OM

  • Brown - Value 4-5 - 3-5% OM

  • Black - Value <3 - >5% OM

How do drainage conditions affect soil colour?

• Poor draining or a fluctuating water table results in a gleyed colour (blue/grey) due to the redox conditions

  • Oxidized Fe3+ turns red due to contact with the air

  • Reduced Fe2+ results in a gleyed colour, as the pigment gets washed away

  • When the water table fluctuates it causes mottles, patches of colour on a background colour

Plinthite

Where ferric iron concentrations harden irreversibly when allowed to dry, resulting in white mottles spots

Soil texture

• The size distribution of individual soil particles into the 3 classes of Clay, silt, and sand with percentage of each in a soil determining the texture class

  • Texture class gives information about what’s going on in a soil

  • Sand (fine or coarse) is the largest, then silt, then clay is the smallest

As particle size decreases, what happens to surface area and reactivity

They increase

How does soil texture influence how soil functions

• Aeration and drainage (sand drains very quickly due to the large space between sand particles)

• Rooting Depth and Volume: Heavy clay soils will become compact or shrink/swell making it difficult for roots to get through, on the flip side sand faces too much erosion for roots to become established

• Fertility: A higher clay content results in more organic matter, adding more nutrients to the soil

• Erosion control: Wind and water can both transport sand and silt, making them susceptible to erosion

Eluviation vs Illuviation

Eluviation: Loss of clay in a downward direction

Illuviation: Accumulation of clay resulting in clay skins (due to eluviation in above layers?)

Varve

An annual accumulation of sediment

Shrink/swell potential

How much clay minerals expand when wet, and shrink when dry, with high shrink/swell potential having the ability to be damaging to anything in it

Soil structure

The combination of sand, silt, and clay into aggregates or Peds

What are the 4 kinds of soil structure?

Structureless, block-like, plate-like, prism-like

What are the classes of soil structure

The size of the aggregates (fine, medium, coarse)

What are the grade of soil structures?

How well can peds be seen in the profile, how distinct are the secondary structural units (weak, moderate, strong)

Consistence

Stability of ped outside the profile, AKA if pinched between fingers would it keep its shape

What’s the difference between prismatic and columnar

• Both are longer than their width and both are vertical

• Columnar has a salt cap

• Prismatic has no salt cap

What is the difference between granular and single grain?

• Granular is clumpy and breaks off in chunks

• Sand is single grain, and won’t find anything granular when it’s just sand

Difference between blocky and platy

• Platy is flat with no clear edge, and is wider than it is tall

• Blocky is irregularly shaped with clear edges

What are the different types of glue that hold peds and aggregates together

• Clay:  the drying/wetting cycles causes shrink/swell, and in the Bt horizon lessivage causes clay build up, making everything more stuck together

• Organic material: Prevents erosion on the Ah horizon due to high biological activity

What can act as anti-glue in peds and aggregates

• Clay and sodium take away the the stability of a structure, removing the glue by trying to avoid each other

• Loss of clay through illuviation means there’s no glue present

Texture

Property inherited from the soil parent material

Structure

Forms in response to pedogenic processes

Which forms first, structure or texture?

Structure always forms after texture (Texture is the building blocks, structure is the castle)

Structural units develop because of:

• Adhesive substances (glue) - Organic matter and Clay

• Forces (compaction, swelling-wetting or freezing, bioturbation (when microbes and soil biota mix up the soil))

• Antiglue - Clay and sodium mixed together will cause a structure to dissolve, and pedogenesis (the loss of clay)

Structure influences soil performance in these ways:s

• Susceptible to erosion (granular particles have more air and are more likely to get blown away)

• Compaction (granular particles have more air and more room to get squished

• Aeration (more space means more air)

• Drainage (more space means more water drainage points)

• Root growth (more airspace means more root growth)

• Microbial activity (looking for a nice cozy home to stay in with lots of air and water)

Factors

The specific conditions that result in the end result of soil, shown by ClORPT

Climate

• Annual precipitation and Annual temperature affect soil

  • Soil temperature ≠ air temperature because of the water content in soil, which can create a lag effect

  • Edmonton is a subhumid region, with a moderate temperature, and dryer precipitation compared to other regions in Canada

  • As temperature decreases, moisture increases in the biomes of Canada (meaning Arctic is the coldest and the wettest)

Organisms

Potential vegetation and Carbon density

Vegetation, what determines it?

• Temperature and precipitation determine the type of vegetation that can grow there and how much

  • Hot and dry = No veg

  • Hot and wet = Lots of veg

  • Cold and wet = Intermediate veg (that’s us!)

Carbon density, what determines it?

• Tied to temp, precipitation, and vegetation because: 

  • Vegetation takes carbon out of the soil and releases into the atmosphere, and roots also store carbon

  • Cold temperatures make it difficult to decompose things, leaving the CO2 trapped in the soil

Relief

Topography, the undulating landscapes creates different soils at different points

The most amount of water will accumulate in the “toe” of the slope, where drainage is the poorest and water builds up from uphill

Aspect

Aspect

• The direction you’re facing, ie if a slope faces South this is a Southern aspect

  • Southern aspects have more evapotranspiration due to increased sun, making them better for grasses and not trees

  • Northern aspects have less evapotranspiration due to less sun, making them better for trees and not grasses

Parent Material

Due to weathering, the parent material breaks down and makes it the basis for the soil above it

What are the two types of weathering?

• Physical weathering: Disintegration of parent material

• Chemical weathering: Erosion of parent material via hydrolysis

Time

Eg: glacier retreat

Water table

While note in ClORP, the water table controls redox (movement of Fe, Mg), how much OM accumulates, and what organisms are there

Human activity

While not part of ClORP, soil management (eg: tillage, irrigations) and adding OM via contamination, can create Anthropogenic soil

Anthropogenic soil

Soil created by the actions of humans

Soil Forming processes

Additions

Loses

Translocations

Transformations

Additions

Adding water (ground water or precipitation), Organic material, eroded material coming from somewhere else

Loses

Gasses (eg: CO2), eroded soil that’s leaving, soil water and solutes leaving

Translocation

The movement of Organic material and clay between horizons via eluviation (loss) and illuviation (gain)

Transformation

Decomposition, nutrient cycling, weathering, everything in the pedon stays in the pedon

Soil formation follows three major steps with the amount done by each affecting the final product:

• 1. The accumulation of parent material

• 2. Soil forming factors affect things on a large scale (ClORPT)

• 3. Horizons are differentiated through soil forming processes (additions, removals, transfers, transformations)

Soil taxonomy

• The grouping of horizons and polypedons based on the properties we can observe in soils

  • Organizes soils based on having a common genesis (sharing the same properties)

  • The system is based on the type and sequence of horizons found in pedons

Uppercase letters (A, B, C) are used to distinguish:

Lowercase suffixes are used to distinguish:

Broad horizons

Specific characteristics

Soil is Classified in a hierarchical system

Order

Great Group

Sub-group

Family

Series

Order, and how many in Canada?

Differentiated based on the effects of the dominant soil forming process, based on the presence or absence of the diagnostic horizon

10 in Canada

Great Group, and how many in Canada?

Indicates the strength of the dominant process, and can be shared by several different orders

31 in Canada

Sub-group, and how many in Canada?

Based on the arrangement of the soil horizons

124 in Canada

Family

The dominant parent material

Series

Grouping based on the pedon

Soil Genesis

The sequence of things that determines how soil forms often graphed with the time on the x-axis, and amount of the specific thing on the y-axis

What are the 5 forms of Soil Genesis?

• Climosequence: Climate

• Biosequence: Organisms

• Lithosequence: Parent material

• Toposequence: Relief

Soil orders focused on in class are

• Chernozems and Solonetz, found in the grasslands

• Podzols, Luvisol, Brunisoil, forest soils that make up the majority of canada after the crysols

Chernozemic Order

Diagnostic horizon is Ah

• Black soils

• Time: 10-15k years ago

• Climate: Continental, semi-arid to subhumid meaning that the climate is water deficient with high carbon storage in the soil, due to the cold and dry conditions causing mainly grasses with adventitious root stems to grow 

  • MAT is above 0 degrees celsius

• Organisms: Dominant vegetation is native grasses

• Parent Material: Fine texture (clay), Glacial Moraine, Glacial Lacustine, Great Western Sediment basin, Calcareous (Parent material has a high base saturation of ions that are Ca2+, Mg2+, K+, Na+)

• Relief: Top of beach lands rolling hills (ie, Edmonton areas above the river valley)

Genetic Concepts for Chernozems: What does it mean to be a Chernozem?

• Leaching of Calcium Carbonate

  • Parent material is generally limestone, which has lots of carbonates

  • Weather provides water and Co2 for the Carbonate to dissociate into a weak acid, leaving behind Calcium in the Ah

  • >80% base saturation due to the increased Ca2+

• Accumulation of Organic Matter

  • Grasses vegetation has a large biomass belowground, due to the roots system

  • Glue: Holds things together, making it a granular structure

  • Pore spaces are created by roots foraging for nutrients and creating structures

  • Colour value is less than 3.5, because Organic Matter is dark

Orthic

means the the normal type which is the closest match to that specific Great Group

Solonetzic Order

• Time: 10-15k years ago

• Climate: Continental, semi-arid to subhumid, cold and dry (same as chernozem)

• Organisms: Vegetation dominated by native grasses (Ah horizon is thick for the same reasons as in Chernozems)

• Parent material: Fine texture (clay), Sodium content must be high with a Na+:Ca2+ greater than ten

• Relief: Beach land to rolling hills, aka same as Chernozem

Toposequence of Solonetzic soils is the same as Chernozems but with 2 additions

• Sodium rich Parent Material that the soil inherits

  • Desalinization or solodization

  • Leaching of Na+ through the profile

• Ground water discharge

  • Sodium leaching accumulates in the area, and salt is left behind by water movement

Issues caused by Solonetzic soils:

• Deflocculation of clay (removal of clay reduces soil structure)

• Osmotic stress (ruins the nutrient gradient plants are using)