Basics for Final Flashcards
What does soil texture refer to?
The relative amount of sand silt and clay as a % of the total volume of the mineral fraction of the soil
Describe the two portions that compose mineral matter.
CFC
- Material > 2mm
Textural Fraction (Sand/Silt/Clay)
Name some soil physical characteristics
color density porosity structure and consistancy drainage horizon configurations plant rooting patterns
How does sand effect the soil?
what is sand composed of? elaborate.
Sand increases the drainage and trafficability of soils by increasimng pore space and aeration.
It is composed of Si02 and is inert due to a full valence shell. Si02 is a product of the chemical weathering of silicate RFM’s but is unique in that it does not provide any nutrients to the soil.
What can be done to minimize erosion on a road?
- Crown surface
- dig deep ditches that will act as a buffer zone
- construct culverts and cross ditches, especially in flashier areas
- construct culverts in a row to minimize catastrophic road failures
What does ped development imply about a soil?
Sign of soil maturity
- higher surface area (for nutrient exchange)
- better drainage (due to increased porosity)
- usually high in stored nutrients
What does high clay and silt content imply about bulk density?
What if it is well structured?
High Clay/Silt = Low bulk density
can have high Pore space if well structured.
Structure relates to pore space/complexity
What is an A horizon called when the colloidal fraction gets washed down into the B horizon?
What is the scientific name of the process of soil being taken from one horizon into another?
The A horizon would become Ae which stands for elluviated.
The process is called translocation and elluviation is downward translocation.
What is an A horizon called when it becomes enriched with organic material from the O horizon?
Ah
which stands for humus enrichment
Describe soil management.
Manipulation of soil in such a way that it will generate specific objectives and values.
Whats the difference between mineral and organic soil?
Mineral soil has less than 17%organic carbon
Organic soil has more than 17%organic carbon
What is a ped?
A ped is a secondary soil structure (composed of primary soil particles)
- sand/silt/clay
- plus binding agents that “glue” them all together like
- OM
- Salts
- Oxides
Define infiltration and percolation
Infiltration: Entry of water into soil
Percolation: Internal drainage (Movement of water through soil)
Define solum
How does it differ from soil
Solum is the upper portion of the soil profile (A and B horizons)
-the part that has undergone physical and chemical weathering
Soil is all the material that sits on top of the bedrock including parent material (C horizon)
Describe the layers of a podzol
What conditions do they develop under
Ae-elluvated (lost colloidal fraction)
Bhf/Bfh- enriched with iron/aluminum and organic colloids from the weathering of Ae
C-ablation till (parent material - usually coarse in podzols)
Podzols develop under cool/cold, moist/wet environments. Normally from coarse textured material.
What are all soils composed of?
MOOHP Mineral matter Organic matter Organisms H20 Pore space (air)
Describe downward development of soil
As forest floor decomposes, humus is translocated into upper mineral soil to create the A horizon. At this point the soil is a regasol (Ah/C) As A horizon thickens, B horizon develops from C horizon via chemical processes and respiration of organisms in soil. The nature of the parent material combined with the climate will eventually determine what type of soil develops from a Regasol.
The material from which solum develops is called?
What are some properties?
Parent material
Tends to be free of OM
As exposed parent material is weathered it will develop into solum. The type of soil is largely dependant on parent material and climate.
Describe soil compaction. What are its results?
Soil compaction is when logging or industrial activity leads to the reduction of pore space. This is common when wet, fine textured soils are driven on by heavy equipment.
Results in
- increased Bd
- reduction of water infiltration and percolation
- reduction of air movement (gas exchange)
- reduction of root penetration
Briefly describe what parent material is…
Unconsolidated material from which solum develops
Often associated with C horizon
What is mottling?
Orange blotches where standing water has caused oxidation reactions with present minerals.
Due to most soils being a function of broken down silicate RFM’s containing iron and aluminum.
Describe the layers of a luvisol.
What conditions do luvisols develop under
Ae- elluviated mineral horizon
Bt- C or Bm horizons enriched with clay from Ae
C-Ablation till
Luvisols develop under cool/cold, moist/wet environments. Usually develop from fine textured parent material.
Explain Isostatic rebound
Expansion of the soil after glacial Ice retreats. Causes ground to rise.
What constituates a mineral?
Inorganic
Crystaline structure
Specific chem. structure eg. SiO2
What percent of minerals are silicates?
90% of roughly 2000 known minerals
Why is relative surface area important?
More surface area = more nutrient exchange
Faster weathering
What is the relative surface areas of the three primary soil particles?
Sand + Silt, relatively low SA
Clay: High SA
Explain a secondary mineral
After full decomposition silicates form a secondary mineral from broken down components of their original structures.
ex. SiO4 + AlO6 = clay
Define Nutrient
anything an organism requires to survive, grow and reproduce
Explain plant nutrient uptake and sources of nutrients.
Most minerals are absorbed by the roots as Ions dissolved in water
Sources:
- Primary (air and rocks) weathering of RFMs
- Secondary (OM)
- Tertiary (internal cycling)
How many essential nutrients are required by trees?
16-18 for growth, development and reproduction
What composes the O horizon
LFH
Litter
Fermentation
Humus
What are some examples of site degradation?
Inappropriate harvesting resulting in :
- Soil puddling
- Soil erosion
- Soil compaction
- Forest floor displacement
- Reforestation of wrong species
- Alteration of microclimate by aggressive harvest
What is a colloidal
what important role does it serve
What are two examples of colloids
All particles smaller than one micron
Source of most nutrients
Clay and Humus are both colloidal in particle size
What is the end product when an RFM is completely weathered?
- Silicon tetrahedron or aluminum octahedron. SiO4 or AlO6.
- The molecules join together to form a lattice with a net (-) charge to which other nutrients and molecules adhere to.
Describe the layers of a chernozem
What conditions form chernozems?
Ah- humus enriched soil (thin in chernozem)
Bm- C horizons that have been moderately weathered to form a brown layer
C- ablation till
Chernozems develop under dry warm climates (grasslands)
Name 3 advantages of having a high CFC
long term nutrient source
soils with high CFC can withstand physical abuse
Soils with high CFC drain more easily
How does silt affect soil?
Spherical shape of particle leads to blockage of pore spaces resulting in poor drainage
cause frost heaving, which breaks up soil leading to site degradation
How is silt produced?
What size are its particles?
Mechanically weathered sand as a function of glacial grinding.
Silt size from 0.05mm-0.002mm
How is clay formed?
Chemical weathering of silicate RFM’s
feldspar, hornblendes, mica etc
What does yellow soil imply about drainage?
Poor Drainage
What does red soil imply about soil?
Drains well (except for mottles!)
Where are luvisols common?
Interior forests with fine textured parent material
Interior forests with fine textured parent material
cool, moist climates
Where are podzols common?
Higher elevations that are cool and wet
coarse textured material
Describe the layers of a brunisol
where are they normally found?
Ah- humus enriched mineral soil horizon
Bm- C horizons that have been moderately weathered to form a brown layer
C-ablation till
Develop under relatively dry, warm climates. Common in CWHxm
Describe the layers of a Regasol
Ah
C
Immature soil
What makes an essential nutrient essential?
Cannot be synthesized by the organism that needs them. Must be obtained from the soil
Define soil
Unconsolidated material that sits on top of bedrock serving as a medium for plant life.
Give several examples of mineral sources of nutrients
Feldspars Hornblendes Sulphides Sulphates Oxides Mica Quartz
There are many more
What is the rock group that gives rise to mineral sources of nutrients?
Silicate rock forming minerals
RFM
Describe what happens in soil puddling
Combination of compaction and re orientation of clay fraction to a horizontal plane
common in wet soils with high clay content
IRREVERSIBLE
what is a pedon?
The smallest 3D unit of soil that can be used to describe a soil
how many groups of brunisols are there?
what do they depend on?
4
depend on thickness of Ah and Ph of soil
what is fluvial material
sediment from streams and rivers. generally coarse and sandy.
What is Lacustrine material?
Silty fine textured material deposited in flood plains
contains allot of silt and clay
where is texture most important?
in the B horizon where the breakdown of parent material takes place
