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Soil Science > Exam 1 > Flashcards

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

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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

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3
Q

How do soils support plant growth?

A

-provide physical support (hold roots)

-air

-water

-temperature moderation

-nutrients

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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

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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

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6
Q

How do soils modify the atmosphere?

A
  1. Direct source of pollutants (if soils aren’t managed correctly)-particulates (dusts)-gasses
  2. Sink for air pollutions
  3. Support for plant growth and microbial activity
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7
Q

What organisms live in soil?

A

worms, snails, beetles, fungi, gophers, bacteria, actinomycetes, protozoa, roundworms, centipedes, millipedes, pillbugs, flatworms

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8
Q

What do humans build with soil?

A

-houses

-ceramics

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9
Q

Why is soil important in engineering?

A

soil types directly influence design of building and roads to ensure longevity and safety

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10
Q

“Big Picture” Goals soil provides

A
  1. Food
  2. Nutrients
  3. Fresh Water
  4. Energy
  5. Climate Change
  6. Biodiversity
  7. Recycling “wastes”
  8. Global Perspective
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11
Q

What are the main soil physical properties?

A
  1. color
  2. texture
  3. texture classes
  4. structure
  5. aggregate
  6. bulk density
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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

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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

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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

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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)

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16
Q

What does soil texture affect?

A

water holding capacity, aeration, drainage, compactability, leaching potential, ability to store plant

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17
Q

Water Holding Capacity

A

Sand: Low
Silt: Medium to High
Clay: High

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18
Q

Aeration

A

Sand: Good
Silt: Medium
Clay: Poor

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19
Q

Drainage

A

Sand: High
Silt: Slow to Medium
Clay: Very slow

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20
Q

Compactability

A

Sand: Low
Silt: Medium
Clay: High

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21
Q

Leaching Potential

A

Sand: High
Silt: Medium
Clay: Low

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22
Q

Store Plant

A

Sand: Low
Silt: Medium
Clay: High

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23
Q

Why does particle size affect so much?

A
  1. Pore Size and Area – affects water and air holding ability
  2. 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
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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

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25
Q

What is texture class?

A

*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

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26
Q

What is a loam soil?

A

*properties of soil are in relatively even percentages
*note this isn’t related to the actual percentages, but the attributes are about equal

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27
Q

What is soil structure?

A

The spatial arrangement of particles to form complete aggregations, pores, and channels

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28
Q

What are aggregates/peds?

A

the structural units of soil structure

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29
Q

What are clods?

A

structures that form when wet soil is plowed or excavated

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30
Q

List the types of soil structure

A

-none (sand dunes and loess soils)
-spheroidal
-plate-like
-block-like
-prism-like
*each can occur at different sizes

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31
Q

How do microorganisms affect soil aggregates?

A

microorganisms help soil aggregates by making them

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32
Q

What is bulk density?

A

*the mass of a unit of volume of dry soil
*the higher the number, the more dense the soil is

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33
Q

What is the typical bulk density of the following soil classes?

A

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

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34
Q

What is soil parent material?

A

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

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35
Q

Three types of parent rock

A

Igneous, Sedimentary, Metamorphic

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36
Q

Igneous

A

*form from magma or lava solidification
*hard, no layer
*ex: granite–intrusive (slow magma cooling) and extrusive (rapid lava cooling)

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37
Q

Sedimentary

A

*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)

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38
Q

Metamorphic

A

*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)

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39
Q

The parent material of the San Joaquin Valley in granite. How did the granite form and where did it come from?

A

*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

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40
Q

What is weathering?

A

*the breakdown of rocks

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41
Q

Physical Weathering

A

temperature or abrasion by water, ice and wind (expand and contract)

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42
Q

Biogeochemical Weathering

A

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

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43
Q

Do all rocks weather at the same rate?

A

No

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44
Q

Hydration Biogeochemical Weathering

A

intact water molecules bind to materials

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45
Q

Hydrolysis Biogeochemical Weathering

A

water molecules split and the hydrogen replaces a cation in the mineral

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46
Q

Dissolution Biogeochemical Weathering

A

water dissolves minerals by hydrating the anions and cations until they become dissociated from each other

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47
Q

Acid Reactions Biogeochemical Weathering

A

acids increase the hydrogen ion activity of water

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48
Q

Oxidation-reduction Reaction Biogeochemical Weathering

A

minerals lose an electron and become oxidized, which destabilizes the mineral structure

49
Q

Complexation Biogeochemical Weathering

A

acids are produced by living organisms, which bind to aluminum in minerals and destroy the structure of the minerals

50
Q

Can multiple forms of weathering occur at once?

A

Yes

51
Q

Residual Parent Material

A

*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
Q

Colluvial Debris

A

*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
Q

Floodplains

A

*during flooding, streams deposit sediments in the calm waters
*each major flooding episode lays down a distinctive layer of sediment

54
Q

Alluvial Fans

A

*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
Q

Deltas

A

*finer sediment settles into the mouths of rivers, forming a poorly draining marsh called a delta

56
Q

Glacier Ice and meltwater

A

glaciers can move on soil and relocate it

57
Q

Organic Deposits like peat bogs

A

an accumulation of organic materials that are drained and deposit

58
Q

Dune Sand

A

hills of sand near oceans and rivers

59
Q

Loess

A

when glaciers recede, wind picks up silt and deposits it up to hundreds of kms away

60
Q

Aerosolic Dust

A

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
Q

Volcanic Ash

A

in areas with active volcanic activity, ash falls on the ground and creates unique soils

62
Q

What are the three primary factors from climate on soil formation?

A

Precipitation, Evaporation, and Leaching (movement of materials down through the soil profile)

63
Q

Humid, Wet Climates

A

*lots of leaching of minerals, especially calcium, sodium and salts
*tend to have infertile soil

64
Q

Dry, arid climates

A

*little to no leaching; accumulation of calcium, sodium and potassium + salts
*add irrigation –> pure water evaporates from the surface and leaves behind salts

65
Q

What factors influence how fast plants change soil?

A

*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
Q

How do humans form soil?

A

-construction
-dams
-agriculture work
-logging
-mining

67
Q

What is a soil profile?

A

*a vertical exposure of soil
*layers of soil are referred to as horizons

68
Q

Master Soil Horizon: O

A

organic layers above the mineral layers

69
Q

Master Soil Horizon: A

A

topmost mineral horizon, contains the most organic matter of the mineral layers

70
Q

Master Soil Horizon: E

A

zones of maximum leaching (“eluviation”) generally lighter in color than the horizons above and below it

71
Q

Master Soil Horizon: B

A

Parent material is usually unrecognizable; contains deposits washed from the E horizon

72
Q

Master Soil Horizon: C

A

Underlying unconsolidated material. In arid soils, contains highest concentrates of carbonates

73
Q

Master Soil Horizon: R

A

Consolidated rock

74
Q

Are horizons a consistent depth?

A

soil horizons may be any depth, from millimeters to meters thick

75
Q

Are all horizons present in all profiles?

A

one or more horizons may not be present in an individual profile

76
Q

Why do we classify soils?

A

group them together based on some characteristics in order to determine how they can be used

77
Q

Pedon

A

an individual “piece” of a soil profile

78
Q

What is a soil series?

A

pedons with the same characteristics (similar to species of plants/animals

79
Q
A
80
Q

Soil Hierarchical System

A

Order-12
Suborder-68
Great Group-444
Subgroup-2500
Family-8000
Series-25000

81
Q

Entisols

A

-little to no profile development
-little in common, other than they are young soils
-found under a wide variety of environmental conditions

82
Q

Inceptisols

A

-beginning “inception” of soil profiles is evident
-slight profile development
-found in variety of conditions

83
Q

Andisols

A

volcanic ash soils

84
Q

Gelisols

A

Permafrost soils

85
Q

Histosols

A

organic soils without permafrost

86
Q

Aridosols

A

dry soils

87
Q

Vertisols

A

dark, swelling, and cracking clays

88
Q

Mollisols

A

dark, soft soils of grasslands

89
Q

Alfisols

A

-accumulation of silicate clays
-moderately leached

90
Q

Ultisols

A

-acidic B Horizon
-heavily leached
-lots of clay

91
Q

Spodosols

A

-acidic
-sandy
-forest soils
-highly leached

92
Q

Oxisols

A

-oxic horizons–iron in soil has oxidized
-highly weathered

93
Q

Soil Percentages

A

25% water, 25% air, 50% soil solids

94
Q

Saturation

A

-all pore space is filled with water
-water will actively drain from soil due to gravity

95
Q

Field Capacity

A

-soil moisture that remains after excess water has drained
-some small air pockets in pore spaces

96
Q

Permanent Wilting Point

A

-there is water in the soil, but it is so rightly adhered to soil particles that plants can’t access it

97
Q

Air Dry

A

-as dry as the soil can get when exposed to air
-a small amount of soil moisture remains

98
Q

Oven Dry

A

-no water left in soil
-all pore spaces filled with air

99
Q

What is available water holding capacity (AWHC) and how is it calculated?

A

-amount of water available to plants
*AWHC= field capacity (FC) - permanent wilting point (PWP

100
Q

After calculating AWHC you must

A

multiple by 12 to convert to inches/foot

101
Q

Soil Moisture Depletion (SMD) Equation

A

-amount of water that’s below field capacity
*SMD=FC-SMC

101
Q

Soil Moisture Content (SMC)

A

-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
Q

Management Allowed Depletion (MAD)

A

-the % of available water holding capacity that management allows to be used up before irrigation

102
Q

Maximum Soil Moisture Depletion (max SMD)

A

-the largest SMD is allowed to become before irrigation
* SMD max = AWHC x MAD

103
Q

How does soil texture affect water holding capacity?

A

Clay-highest water holding capacity
OM-highest WHC
Silt- Moderate WHC
Sand- Low

104
Q

How does soil texture affect water tension?

A

Clay= highest soil water tensions
Silt=moderate soil water tension
sand=low soil water tension

105
Q

Hand move or wheel move sprinkler systems

A

-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
Q

Furrows and Border Strips with long runs or sandy soils

A

-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
Q

Specific Plant Requirements

A

*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
Q

Irrigation Systems Capable of Small, frequent irrigation

A

-micro irrigation
-solid and permanent set sprinklers
-center pivot and linear move

109
Q

Irrigation with saline (salty) water

A

-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
Q

Uncertain water supply

A

-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
Q

Specific Plant Requirements

A

-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
Q

Properties of water

A

cohesion, adhesion, capillary action, and polarity

113
Q

Cohesion

A

water molecules are attracted to each other

114
Q

Adhesion

A

water molecules are attracted to others

115
Q

Capillary Action

A

the movement of water within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension

116
Q

Polarity

A

Unequal sharing of electrons makes water a polar molecule.

117
Q

Capillary Action/Tension in Clay Soils and Sandy Soils

A

Clay Soil have higher capillary action/tension, while sandy soils have lower capillary action/tension

Soil Science (3 decks)

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