Basics for Final Flashcards
(56 cards)
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
