Section 3: Soil Classification Flashcards
Soil Classification is based on the characteristics that can be observed in a soil profile.
- A soil profile is a vertical slice of the soil through all its horizons:
- Major Mineral Horizons are…
- Major Organic Horizons are L, F, H, and O
Two observable mineral horizon characteristics are color and structure (the shapes of soil peds) which usually change distinctly at the horizon border
A, B and C
Master soil horizons are more completely described by attaching a lower case suffix such as:
Ah, Bt or Ck.
Ah indicates an A horizon that has been enriched with organic matter (?).
Bt indicates a B horizon that has accumulated fine ? particles from above.
Ck is a C horizon enriched with ?
humus
clay
carbonates
(k sound)
Horizon Suffixes
Typical Soil Profiles
Two of the most common soil profiles in western Canada are
Grasslands are found in the warmer, drier areas to the south while forests develop in the cooler, more humid climate to the north, east and west of the prairies
grassland and forest soils
The Canadian System of Soil Classification
(CSSC) – A hierarchical system which begins by separating soils into one of ten broad categories called Orders
Orders are determined by characteristics of the … (A, B and C) that reflect the dominant soil forming processes
Master Soil Horizon
The Canadian System of Soil Classification (CSSC)
A hierarchical system which begins by separating soils into one of ten broad categories called Orders
Orders are determined by characteristics of the Master Soil Horizon (A, B and C) that reflect the dominant soil forming processes –
Orders are divided into subcategories: Great Groups, Subgroups, Families and finally Series. –
Soils of the same series have…
similar kinds and arrangements of horizons whose
- color,
- texture,
- structure,
- consistence,
- thickness,
- reaction and
- composition fall into a very narrow range.
Orders are divided into subcategories:
Great Groups,
Subgroups,
Families and
finally Series.
Peat moss is the dried and decayed form of Sphagnum moss.
Peat moss is often mixed with soil to increase the soil’s ability to retain moisture and nutrients, and regulate the air
Solonetzic soils occur in the same ecozones (Prairies and Boreal Plains) as Chernozemic soils.
The distinction between the two orders arises from the effect of a particular positively charged ion (or base cation) on soil formation and properties – ? (Na+).
The high amount of sodium is recognized by the n suffix
Bn
sodium
In soils of the Chernozemic order, the main base cations released from weathering of the glacial sediments are ? and, to a lesser extent,?
calcium (Ca2+)
magnesium (Mg2+)
Simple Definition of Soil
Not everything found at the Earth’s surface can be called soil. To be classified as soil t
the surface material must be
unconsolidated (loose),
must occur naturally and
usually appears as distinct layers that are visible from a side view
The Four Fundamental Components of Soil The four fundamental components of soil are:
1.
- Organic Matter
3.
- Water
- Mineral Material
- Air
The solum refers to the
upper two horizons in which the most soil development has occurred.
The proportions of mineral and organic components change very slowly in soils but the proportions of water and air vary constantly depending on moisture supply. The percentage of air and water has a large impact on soil productivity. Optimum moisture content for plant growth is about… (50% of the total pore volume).
Air simply occupies the pore space (spaces between soil particles) not filled with water.
25% of total soil volume
Minerals are the ?, crystalline compounds found in rocks that make up the majority of soil particles in most soils.
non-living
Mineral particles cover a ??? from small rock fragments down to the tiniest clay particles which can be observed only with electron microscopes.
wide range of sizes
Although most soil minerals have a crystalline structure, some highly weathered secondary minerals are ? or non-crystalline in nature
amorphous
Soils can be composed of a huge variety of mineral compounds.
Two soil samples will differ in the proportions of minerals they contain and their particle sizes because soils originate from different ?? and have been exposed to different degrees of weathering.
parent materials
General categories of minerals common to western Canadian soils include ??, secondary minerals and carbonate minerals.
Minerals are important to soils because they dictate the soil ? which has a big influence on soil
- pH,
- salinity,
- fertility and
- structure.
primary minerals
chemistry
Primary Minerals
Primary minerals have remained relatively unchanged in composition since they formed from cooling lava
?, the most common example, can be easily observed under a microscope as shiny, clear crystals common in sand samples. Primary minerals found in soils are resistant to weathering (breakdown).They are usually large particles that contribute to air and water movement but are less important for fertility or water holding capacity
Quartz
Secondary minerals include
silicate clays and iron or aluminum oxides
which have been formed over time from the weathering processes that break down ??.
Figure A3-3 illustrates that primary minerals dominate the coarse particle sizes and secondary minerals make up the majority of the fine-sized particles. Secondary minerals influence important soil properties including ? and ?
primary minerals
fertility and water holding capacity
Carbonate minerals are a special group of secondary minerals that are composed mainly of
These minerals originated in the limestone bedrock that was crushed by ? ice sheets as they moved across the continent.
There are also numerous secondary minerals that have been formed by dissolving of primary carbonates and their precipitation or recrystallization in a modified form.
calcite (CaCO3 ) and dolomite (CaMg(CO3 )2 ).
glacial
Carbonate minerals maintain ? in soils, and
provide essential nutrients for plant growth (calcium and magnesium).
alkaline pH (>7)
Carbonate minerals may interfere with plant growth when present in ? amounts.
Carbonate levels in surface horizons usually decrease over time due to leaching from rainfall and natural acids.
high
