General soil Flashcards
What are 5 reasons we should examine soils?
- Food production (through crops)
- Provides a metric of biological diversity
- Carbon cycling
- Water quality
- Plant respiration/photosynthesis
What are the 6 main functions of soil?
- Water supply & purification
- Medium for plant growth
- Habitat for organisms
- Nutrient/waste recycling
- Engineering medium
- Atmospheric modifier
What are the 4 soil forming processes?
- Transformation
- Translocation
- Addition
- Loss
What are the 3 common soil physical properties?
- Density
- Texture
- Color
FITB: Soil textures can have different ____________ for sands, silt and clay
Thresholds
FITB: Sands are mainly composed of ______ grains
Quartz
How do sands feel?
Gritty
T/F: Sand grains are not visible to the naked eye
False; they are
Do sands have high or low surface areas?
Low
Why are plants unable to grow in sandy soils?
Because there are very few nutrients found within sands
T/F: Sand cannot store water
True
Does water move slowly or quickly through sand?
Quickly
FITB: Silts are composed of ____-sand particles
Micro
What does silt feel like?
Smooth, chalky, like flour
T/F: Silt is sticky when wet
False
T/F: Silt particles can be seen by the naked eye with no microscope needed
False; visible in field lens
T/F: Silt can hold more water than sand
True
Does silt have a higher or lower surface area?
Higher
What is a unique characteristic of silt?
It releases plant-available nutrients
What is the texture of clay like?
How does it appear to the eye?
Flat; plate-like
How is clay formed?
From weathering
What does clay feel like?
Sticky, plastic-like
T/F: Clay can be molded
True; think of art projects you did as a kid
FITB: When clay is dry, it can be described as a ____ mass
Hard
Does physical or chemical weathering occur with clay?
Chemical
T/F: Clay cannot shrink nor can it swell
False; it can do both of these things
Does clay have a high or low surface area?
Very high
Soil textural classes are made up of ______, ________, & _______
- Sand
- Silt
- Clay
T/F: Soil color does control the processes within the soil
False
TOT: Soil color can indicate that something has stayed the same/changed in the soil
Changed
Color wise, what colors make up a soil with silts & clays?
Brown, tan, yellow
How can you tell if there is a lack of other particles such as silt and clay?
If there is only sand left in the soil
T/F: The wetter the soil, the lighter it will be
False! It will definitely be darker in color
What does oxidation state mean?
The availability of oxygen within the soil
If you have oxidized iron, what color is going to appear?
Rust color (orange)
When iron is reduced, what color does it become?
Gray
Oxidized environments can be associated with well/poor drained environments?
Well-drained
T/F: Reduction is the opposite of oxidation
True
What is the Munsell Color System?
A book that contains a numerical system in which one can associate soil sample colors with (to compare)
Munsell colors are arranged according to 3 features; which are these 3 features? (in order)
- Hue - how red/yellow (10YR)
- Value - Light or dark (8-light, 1-dark)
- Chroma - Brightness/intensity
10YR 5/3 is an example of a _________ color
Munsell
T/F: Volcanic rocks can make soil black/dark
True
Does dark soil always mean that is organic matter?
No
Name the process: very little presence of oxygen is called ________ while an abundance of water + oxygen + iron is called ________
- Reduction
- Oxidation
T/F: Volcano soils are not rich or fertile due to their lack of organic matter
False
Is agriculture successful in places with volcano soils? Why?
Yes because they have rich & fertile soils with organic matter that cannot breakdown (so it stays still)
Pine trees add ______ to soil profiles
Acids
Pure sands come from _________
Quartz
T/F: Calcium/sodium deposits can make white layers within soils
True!
Soil structure is made up of the arrangement of sand, silt, clay and organic matter which forms into ____________
Aggregates
What are aggregates?
Smaller particles that come together that form a larger particle
Why do aggregates form/come together?
Because of soil glue (sticky stuff)
FITB: Aggregate formations can be in a ________, _______ or ________ form
- Physical
- Chemical
- Biologic
FITB: Aggregates have the ability to shrink/_____, and ______/thaw
- Swell
- Freeze
What is flocculation?
The attraction of 2 particles together due to charges/the mutual attraction among clay and organic molecules (like magnets)
Aggregate formation dispersion (breaking apart the structure) occurs with which common element?
Sodium
FITB: Aggregate formation can occur with exudate, _______ or living matter
Residue
What are the 5 main structural shapes of soils?
- Granular - found at surface
- Blocky - found underground
- Platy - flat, sign of compaction occurring
- Prismatic/Columnar - forms in lower B/C horizons, lots of clay, column-like
- Structureless - Single grain, massive clays that are random + chunky
What are the 5 factors that affect Bulk Density?
- Organic matter
- Poor aggregation
- Grain size
- Soil flora + fauna
- Depth of sample
What is porosity?
The amount of empty space found within soils
MC: The amount of empty space (porosity) in clays is…
A. Poorly aggregated
B. Somewhat aggregated
C. Well-aggregated
D. Compacted
C. Well-aggregated
Do clays hold more or less organic matter?
More
Are the pores in clays smaller or larger? (Consider particle size and if it can be seen with the naked eye)
Smaller (more pore space)
MC: The amount of empty space (porosity) in sands is…
A. Poorly aggregated
B. Somewhat aggregated
C. Well-aggregated
D. Compacted
A. Poorly aggregated
Does sand hold more or less organic matter?
Less (remember that plants can’t live in sandy soils)
Is the pore space in sand less or more?
Less
Are sand particles small or large?
Large
Low %’s of pore space indicate that what process is occurring within the soil?
Compaction
FITB: As % pore space goes down, bulk density goes ___
Up
FITB: As % pore space goes up, bulk density goes _____
Down
What is the numerical value for Particle Density?
2.65 g/cm³
What kind of soil is bulk density composed of?
Dry soil
What is Bulk Density?
The weight of a soil in a known volume
What is Soil Pore Space?
The % of volume occupied by air & water
Bulk Density includes solid + ______ fractions
Pore
Why is Bulk Density important?
For agriculture
TOT: If you have a higher Bulk Density, that means that you have more/less compaction
More
TOT: If you have a lower Bulk Density, that means that you have more/less compaction
Less
What is the ideal Bulk Density numerical range for plant growth?
1.2-1.4
TOT: When you have higher compaction, it is harder/easier to have air and water pass through the soil
Harder
T/F: Minerals are less dense than water
False
T/F: Organic matter is more dense than water
True
What are the 5 soil forming factors?
- Climate
- Biota
- Relief (topography)
- Parent material
- Time
What is climate?
The change in atmospheric conditions
T/F: Climate does not influence erosion, plant success or mineral breakdown
False
When we talk about relief being one of the 5 soil forming factors, what are we really referring to? (Don’t say topography)
How hilly/flat your landscape is
Relief includes what 5 characteristics?
- Slope
- Length
- Landscape position
- Elevation
- Aspect
FITB: One of the soil forming factors is time. Time controls the amount of _________ occurring
Interactions
Time includes what 3 characteristics?
- Climate
- Vegetation
- Human interactions
Biota is composed of _________ __________.
Living organisms
What are 4 examples of biota?
- Microbes
- Animals
- Plants
- Humans
T/F: Microbes participate in biological processes such as the act of nitrification
True
FITB: Microbes _______ organic matter
Nitrify
FITB: Earthworms create _______ in their guts
Calcite
What is Pedoturbation?
The physical disturbance & mixing of soil horizons (performed by worms and roots)
T/F: Humans were a major force of soil development in the past but no longer are today
False
What are the 4 characteristics of Human Influences?
- Building development
- Waste
- Agriculture
- Climate
What is parent material?
The material and process from which soil develops
What is weathering?
The deterioration of rock due to breakdown processes
What are the 2 types of weathering?
- Physical (mechanical)
- Chemical
FITB: A physical type of weathering is known as ______’s sandpaper, which is more commonly known as _______ & ________
- Nature’s
- Impact & abrasion
What are 3 things that can cause Impact & abrasion to occur?
- Wind
- Water
- Ice
What is meant by impact and abrasion?
Carried particles that scrape against a substance (like a rock)
How do grooves (a physical weathering type) form?
When a bigger rock scrapes against bedrock (in which ice then picks it up and carries it across)
Is Wedging a physical/chemical type of weathering?
Physical
How does wedging occur?
When water enters into cracks of rocks and the water within freezes, the rock expands
T/F: Wedging affects small and larger objects
False; just larger objects
T/F: Wedging can occur through plants and trees
True
Exfoliation is an example of a physical/chemical type of weathering?
Physical
What does Exfoliation mean?
The loss of the outer layer of a rock due to expansion
Stratification occurs in which type of rock?
A. Limestone
B. Granite
C. Coal
D. Quartz
E. Bedrock
E. Bedrock
T/F: Stratification does not need to have some movement (sunlight)
False
Stratification is associated with which type of physical weathering?
A. Impact & abrasion
B. Hydration
C. Grooves
D. Exfoliation
D. Exfoliation
