Exam 1 Flashcards
1
Q
Why is soil health and quality more important in the future?
A
-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
2
Q
What ecosystem services do soils perform?
A
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
3
Q
How do soils support plant growth?
A
-provide physical support (hold roots)
-air
-water
-temperature moderation
-nutrients
4
Q
How do soils regulate water supplies?
A
-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
5
Q
How do soils recycle raw materials?
A
decompose dead plants, animals and other organisms, and make nutrients and other raw materials available to living organisms
6
Q
How do soils modify the atmosphere?
A
- Direct source of pollutants (if soils aren’t managed correctly)-particulates (dusts)-gasses
- Sink for air pollutions
- Support for plant growth and microbial activity
7
Q
What organisms live in soil?
A
worms, snails, beetles, fungi, gophers, bacteria, actinomycetes, protozoa, roundworms, centipedes, millipedes, pillbugs, flatworms
8
Q
What do humans build with soil?
A
-houses
-ceramics
9
Q
Why is soil important in engineering?
A
soil types directly influence design of building and roads to ensure longevity and safety
10
Q
“Big Picture” Goals soil provides
A
- Food
- Nutrients
- Fresh Water
- Energy
- Climate Change
- Biodiversity
- Recycling “wastes”
- Global Perspective
11
Q
What are the main soil physical properties?
A
- color
- texture
- texture classes
- structure
- aggregate
- bulk density
12
Q
How is color measured for soil?
A
-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
13
Q
Why do we measure color of wet and dry soil?
A
soil colors can be different when they are wet vs when they are dry
14
Q
What is soil texture?
A
-the relative % of sand, silt, and clay in a soil
-whether soil particles are sand, silt, or clay depends on their size
15
Q
What size are the following soil texture particles?
A
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)
16
Q
What does soil texture affect?
A
water holding capacity, aeration, drainage, compactability, leaching potential, ability to store plant
17
Q
Water Holding Capacity
A
Sand: Low
Silt: Medium to High
Clay: High
18
Q
Aeration
A
Sand: Good
Silt: Medium
Clay: Poor
19
Q
Drainage
A
Sand: High
Silt: Slow to Medium
Clay: Very slow
20
Q
Compactability
A
Sand: Low
Silt: Medium
Clay: High
21
Q
Leaching Potential
A
Sand: High
Silt: Medium
Clay: Low
22
Q
Store Plant
A
Sand: Low
Silt: Medium
Clay: High
23
Q
Why does particle size affect so much?
A
- 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
24
Q
Why is surface area an important factor in the qualities of soil?
A
the greater the surface area, the more microorganisms there are present
25
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
26
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
27
What is soil structure?
The spatial arrangement of particles to form complete aggregations, pores, and channels
28
What are aggregates/peds?
the structural units of soil structure
29
What are clods?
structures that form when wet soil is plowed or excavated
30
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
31
How do microorganisms affect soil aggregates?
microorganisms help soil aggregates by making them
32
What is bulk density?
*the mass of a unit of volume of dry soil
*the higher the number, the more dense the soil is
33
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
34
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
35
Three types of parent rock
Igneous, Sedimentary, Metamorphic
36
Igneous
*form from magma or lava solidification
*hard, no layer
*ex: granite--intrusive (slow magma cooling) and extrusive (rapid lava cooling)
37
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)
38
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)
39
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
40
What is weathering?
*the breakdown of rocks
41
Physical Weathering
temperature or abrasion by water, ice and wind (expand and contract)
42
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
43
Do all rocks weather at the same rate?
No
44
Hydration Biogeochemical Weathering
intact water molecules bind to materials
45
Hydrolysis Biogeochemical Weathering
water molecules split and the hydrogen replaces a cation in the mineral
46
Dissolution Biogeochemical Weathering
water dissolves minerals by hydrating the anions and cations until they become dissociated from each other
47
Acid Reactions Biogeochemical Weathering
acids increase the hydrogen ion activity of water
48
Oxidation-reduction Reaction Biogeochemical Weathering
minerals lose an electron and become oxidized, which destabilizes the mineral structure
49
Complexation Biogeochemical Weathering
acids are produced by living organisms, which bind to aluminum in minerals and destroy the structure of the minerals
50
Can multiple forms of weathering occur at once?
Yes
51
Residual Parent Material
*forms in place from weathering of the underlying rock
*in wet climates, residual parent material is usually leached and oxidized
*in dry climates, the residual parent material closely resembles the rock from which it formed
52
Colluvial Debris
*made up of rocks detached from above and carried down slope, usually by gravity
*usually coarse and stony, with angular rocks (because of physical weathering)
53
Floodplains
*during flooding, streams deposit sediments in the calm waters
*each major flooding episode lays down a distinctive layer of sediment
54
Alluvial Fans
*streams leave a narrow valley and deposit sediment in the shape of a fan over a much larger area
*Central Valley is an example
55
Deltas
*finer sediment settles into the mouths of rivers, forming a poorly draining marsh called a delta
56
Glacier Ice and meltwater
glaciers can move on soil and relocate it
57
Organic Deposits like peat bogs
an accumulation of organic materials that are drained and deposit
58
Dune Sand
hills of sand near oceans and rivers
59
Loess
when glaciers recede, wind picks up silt and deposits it up to hundreds of kms away
60
Aerosolic Dust
very fine particles stay in the air for thousands of kms, before being deposited with rainfall
*most of the calcium carbonate in the soil in the Western US is from the saharan desert
61
Volcanic Ash
in areas with active volcanic activity, ash falls on the ground and creates unique soils
62
What are the three primary factors from climate on soil formation?
Precipitation, Evaporation, and Leaching (movement of materials down through the soil profile)
63
Humid, Wet Climates
*lots of leaching of minerals, especially calcium, sodium and salts
*tend to have infertile soil
64
Dry, arid climates
*little to no leaching; accumulation of calcium, sodium and potassium + salts
*add irrigation --> pure water evaporates from the surface and leaves behind salts
65
What factors influence how fast plants change soil?
*ability of plants to take up calcium ions
-low calcium = slow leaf decomposition and larger accumulations of organic matter on the soil surface)
*rooting depth
*plant size
66
How do humans form soil?
-construction
-dams
-agriculture work
-logging
-mining
67
What is a soil profile?
*a vertical exposure of soil
*layers of soil are referred to as horizons
68
Master Soil Horizon: O
organic layers above the mineral layers
69
Master Soil Horizon: A
topmost mineral horizon, contains the most organic matter of the mineral layers
70
Master Soil Horizon: E
zones of maximum leaching ("eluviation") generally lighter in color than the horizons above and below it
71
Master Soil Horizon: B
Parent material is usually unrecognizable; contains deposits washed from the E horizon
72
Master Soil Horizon: C
Underlying unconsolidated material. In arid soils, contains highest concentrates of carbonates
73
Master Soil Horizon: R
Consolidated rock
74
Are horizons a consistent depth?
soil horizons may be any depth, from millimeters to meters thick
75
Are all horizons present in all profiles?
one or more horizons may not be present in an individual profile
76
Why do we classify soils?
group them together based on some characteristics in order to determine how they can be used
77
Pedon
an individual "piece" of a soil profile
78
What is a soil series?
pedons with the same characteristics (similar to species of plants/animals
79
80
Soil Hierarchical System
Order-12
Suborder-68
Great Group-444
Subgroup-2500
Family-8000
Series-25000
81
Entisols
-little to no profile development
-little in common, other than they are young soils
-found under a wide variety of environmental conditions
82
Inceptisols
-beginning "inception" of soil profiles is evident
-slight profile development
-found in variety of conditions
83
Andisols
volcanic ash soils
84
Gelisols
Permafrost soils
85
Histosols
organic soils without permafrost
86
Aridosols
dry soils
87
Vertisols
dark, swelling, and cracking clays
88
Mollisols
dark, soft soils of grasslands
89
Alfisols
-accumulation of silicate clays
-moderately leached
90
Ultisols
-acidic B Horizon
-heavily leached
-lots of clay
91
Spodosols
-acidic
-sandy
-forest soils
-highly leached
92
Oxisols
-oxic horizons--iron in soil has oxidized
-highly weathered
93
Soil Percentages
25% water, 25% air, 50% soil solids
94
Saturation
-all pore space is filled with water
-water will actively drain from soil due to gravity
95
Field Capacity
-soil moisture that remains after excess water has drained
-some small air pockets in pore spaces
96
Permanent Wilting Point
-there is water in the soil, but it is so rightly adhered to soil particles that plants can't access it
97
Air Dry
-as dry as the soil can get when exposed to air
-a small amount of soil moisture remains
98
Oven Dry
-no water left in soil
-all pore spaces filled with air
99
What is available water holding capacity (AWHC) and how is it calculated?
-amount of water available to plants
*AWHC= field capacity (FC) - permanent wilting point (PWP
100
After calculating AWHC you must
multiple by 12 to convert to inches/foot
101
Soil Moisture Depletion (SMD) Equation
-amount of water that's below field capacity
*SMD=FC-SMC
101
Soil Moisture Content (SMC)
-amount of water that exists in soil at a particular time
-changes daily as plants take up water in their normal growth processes
-may be measured as % water by mass, % water by volume, inches of water per foot of soil
101
Management Allowed Depletion (MAD)
-the % of available water holding capacity that management allows to be used up before irrigation
102
Maximum Soil Moisture Depletion (max SMD)
-the largest SMD is allowed to become before irrigation
* SMD max = AWHC x MAD
103
How does soil texture affect water holding capacity?
Clay-highest water holding capacity
OM-highest WHC
Silt- Moderate WHC
Sand- Low
104
How does soil texture affect water tension?
Clay= highest soil water tensions
Silt=moderate soil water tension
sand=low soil water tension
105
Hand move or wheel move sprinkler systems
-large MAD appropriate for this situation
-require a significant amount of time to get through their complete cycle
-time between irrigations must be long, the MAD must be relatively large
106
Furrows and Border Strips with long runs or sandy soils
-large MAD appropriate for this situation
-require a minimum amount of water just to get the water across the field
-difficult to apply small amount uniformly
-larger application = larger irrigation intervals
107
Specific Plant Requirements
*moisture stress--longer irrigation intervals so larger MADS
ex: almonds prior to harvesting
-citrus prior to bud formation
-cotton to promote set/growth of bolls rather than excessive vegetative growth
-wine grapes prior to harvesting
-some trees/vines prefer stress prior to winter. The stress to "harden" the plant, and reduces liquid sap in trucks to avoid frost damage
108
Irrigation Systems Capable of Small, frequent irrigation
-micro irrigation
-solid and permanent set sprinklers
-center pivot and linear move
109
Irrigation with saline (salty) water
-total stress on the plant is the sum of moisture stress and osmotic (due to salinity) stress
-to minimize total stress, irrigations should be scheduled so that moisture stress remains low, which calls for relatively small MAD
110
Uncertain water supply
-large depletions must be avoided because
- if water becomes unavailable when the depletion is already large, soil moisture tension and plant stress may get too high before irrigation is possible again
111
Specific Plant Requirements
-high moisture and low tension correspond to small MAD
-root crops like carrot, onion and potatoes need small MAD
-stone fruit (peaches, cherries)
-strawberries
-corn is sensitive to stress during pollination stage
112
Properties of water
cohesion, adhesion, capillary action, and polarity
113
Cohesion
water molecules are attracted to each other
114
Adhesion
water molecules are attracted to others
115
Capillary Action
the movement of water within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension
116
Polarity
Unequal sharing of electrons makes water a polar molecule.
117
Capillary Action/Tension in Clay Soils and Sandy Soils
Clay Soil have higher capillary action/tension, while sandy soils have lower capillary action/tension
