Exam 1 Flashcards
Why is soil health and quality more important in the future?
-we depend on soils for food
-demand increases as population increases
-amount/quality of soil is decreasing because of soil degradation and urbanization
-we may also depend on plant resources to provide us with materials as oil reserves deplete
What ecosystem services do soils perform?
Provisioning: providing goods such as water, food, lumber, raw materials such as clay for bricks, all ceramics (dishes, tile, etc.)
Regulating: processes that purify water, decompose water, control pests, or modify atmospheric gases
Supportive: assisting with nutrient cycling, seed dispersal, primary biomass production
Cultural: scenic views, outdoor activities
How do soils support plant growth?
-provide physical support (hold roots)
-air
-water
-temperature moderation
-nutrients
How do soils regulate water supplies?
-help convert non-drinkable water into drinkable water
-act as a water purifier–physical, chemical, and biological
-physical filtration–filters out contaminants
-chemical filtration– contaminants attach to soil particles
-biological filtration–bacteria & fungi break down contaminants
How do soils recycle raw materials?
decompose dead plants, animals and other organisms, and make nutrients and other raw materials available to living organisms
How do soils modify the atmosphere?
- Direct source of pollutants (if soils aren’t managed correctly)-particulates (dusts)-gasses
- Sink for air pollutions
- Support for plant growth and microbial activity
What organisms live in soil?
worms, snails, beetles, fungi, gophers, bacteria, actinomycetes, protozoa, roundworms, centipedes, millipedes, pillbugs, flatworms
What do humans build with soil?
-houses
-ceramics
Why is soil important in engineering?
soil types directly influence design of building and roads to ensure longevity and safety
“Big Picture” Goals soil provides
- Food
- Nutrients
- Fresh Water
- Energy
- Climate Change
- Biodiversity
- Recycling “wastes”
- Global Perspective
What are the main soil physical properties?
- color
- texture
- texture classes
- structure
- aggregate
- bulk density
How is color measured for soil?
-soils can be many colors depending on parent material and degree of weathering
-some colors of dye and paint are still obtained from soil
-measured using a Munsell Color Chart–contains chips of color that you match to your soil sample wet and dry
Why do we measure color of wet and dry soil?
soil colors can be different when they are wet vs when they are dry
What is soil texture?
-the relative % of sand, silt, and clay in a soil
-whether soil particles are sand, silt, or clay depends on their size
What size are the following soil texture particles?
Sand: between 0.06-2mm (largest pore size, smallest pore space)
Silt: between 0.003-0.05mm (moderate pore size and pore space)
Clay: under 0.002mm (smaller pore size, largest pore space)
What does soil texture affect?
water holding capacity, aeration, drainage, compactability, leaching potential, ability to store plant
Water Holding Capacity
Sand: Low
Silt: Medium to High
Clay: High
Aeration
Sand: Good
Silt: Medium
Clay: Poor
Drainage
Sand: High
Silt: Slow to Medium
Clay: Very slow
Compactability
Sand: Low
Silt: Medium
Clay: High
Leaching Potential
Sand: High
Silt: Medium
Clay: Low
Store Plant
Sand: Low
Silt: Medium
Clay: High
Why does particle size affect so much?
- Pore Size and Area – affects water and air holding ability
- Surface Area
*all soils have a slight negative charge (anionic)
*the greater the surface area, the greater the negative charge
*influences the exchange of cations (many of which are plant nutrients) on the soil particle surface
Why is surface area an important factor in the qualities of soil?
the greater the surface area, the more microorganisms there are present
What is texture class?
*soil texture triangle is used to place different combinations of textures into classes
*soils may also have different amounts of gravel and organic matter that further modify soil
What is a loam soil?
*properties of soil are in relatively even percentages
*note this isn’t related to the actual percentages, but the attributes are about equal
What is soil structure?
The spatial arrangement of particles to form complete aggregations, pores, and channels
What are aggregates/peds?
the structural units of soil structure
What are clods?
structures that form when wet soil is plowed or excavated
List the types of soil structure
-none (sand dunes and loess soils)
-spheroidal
-plate-like
-block-like
-prism-like
*each can occur at different sizes
How do microorganisms affect soil aggregates?
microorganisms help soil aggregates by making them
What is bulk density?
*the mass of a unit of volume of dry soil
*the higher the number, the more dense the soil is
What is the typical bulk density of the following soil classes?
Uncultivated loamy soils: 0.8-1.1
Cultivated clay and silt loams: 0.9-1.5
Cultivated sandy loams and sands: 1.25-1.75
What is soil parent material?
what types of rocks and minerals the soil was made out of originally, each rock and mineral lends specific characteristics to the soil, helps us understand the uses and preservation of the soil
Three types of parent rock
Igneous, Sedimentary, Metamorphic
Igneous
*form from magma or lava solidification
*hard, no layer
*ex: granite–intrusive (slow magma cooling) and extrusive (rapid lava cooling)
Sedimentary
*forms from sediment compaction
*crumbly, layered
*ex: sandstone–clastic (compacted pieces of broken rocks), limestone–chemical (compacted dissolved materials), and Coal–organic (compacted biogenic matter)
Metamorphic
*forms by transformation of other rocks
*relatively hard, may or may not have layers
*ex: slate–foliated (has layers) and marble–non-foliated (no layers)
The parent material of the San Joaquin Valley in granite. How did the granite form and where did it come from?
*formed from igneous rock
*lava within sierras was cooling very slowly –> turns into granite
*as sierras break down, the granite gets more exposed
*snow melt dragged granite pieces down to the valley floor
What is weathering?
*the breakdown of rocks
Physical Weathering
temperature or abrasion by water, ice and wind (expand and contract)
Biogeochemical Weathering
all other processes, direct or indirect, by which living organisms and their metabolic processes and products affect the chemical stability and composition of silicate rocks and minerals
Do all rocks weather at the same rate?
No
Hydration Biogeochemical Weathering
intact water molecules bind to materials
Hydrolysis Biogeochemical Weathering
water molecules split and the hydrogen replaces a cation in the mineral
Dissolution Biogeochemical Weathering
water dissolves minerals by hydrating the anions and cations until they become dissociated from each other
Acid Reactions Biogeochemical Weathering
acids increase the hydrogen ion activity of water