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Environmental Science 2000 > Soil and Soil Resources > Flashcards

Soil and Soil Resources Flashcards

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1
Q

what does soil consists of

A
  • mineral matter and decaying matter
  • organic matter
    (dead and decaying microorganisms, plants and animal matter)
  • air (not the same as we breath)
  • water (not pure but holds dissolved minerals and organics for plant growth)
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2
Q

what are some biotic communities in soil

A
  1. microorganisms
  2. larger organisms (earthworms, burrowing mammals, amphibians and reptiles)
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3
Q

how does soil formation begin

A

with the breakdown of parent rock by weathering (exposure to atmosphere, hydrosphere and biosphere)

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4
Q

what do soil profiles consists of

A

distinct layers (horizons)

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5
Q

why do soil profiles form

A

a result of weathering combined with leaching

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6
Q

why is soil crucial in supporting life

A

they are crucial for providing nutrients for plant growth which support life

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7
Q

how do materials for plant growth move from soil to soil solution and back

A

through ion exchange

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8
Q

how is human population growth and pressures of agriculture affecting soil

A

it is degrading soils which results in us losing topsoil from productive croplands

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9
Q

main mechanisms of soil loss

A
  • water erosion

wind erosion (aeolian erosion)

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10
Q

is desertification a natural process or artificial process

A

natural process

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11
Q

is accelerated erosion a natural process or artificial process

A

artificial - caused by human activities

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12
Q

what are some (agricultural) ways to protect soils from erosion

A
  1. crop rotation
  2. contour farming
  3. intercropping
  4. terracing
  5. shelterbelts and buffer zones
  6. reduced tillage
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13
Q

what can overirrigation cause

A

salinization and waterlogging

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14
Q

how does overirrigation affect crop yields

A

lower crop yields

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15
Q

how does overgrazing affect soils

A

causes soil compaction and degradation

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16
Q

why is it important to preserve grasses on rangelands

A

to protect soils from the effects of overgrazing

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17
Q

is soil and rock the same thing

A

NO - soil is a complex plant supporting system and not a loose material derived from rock

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18
Q

what is the most common parent material for soil

A

bedrock (the continuous mass of solid rock comprising earth’s crust)

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19
Q

weathering

A

The physical, chemical and biological processes that break down rocks and minerals

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20
Q

humus

A

Dark, spongy, crumbly mass of material made of up complex organic compounds

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21
Q

describe soil with high humus content

A

hold more moisture and are more productive for plant life

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22
Q

peat

A

Soils that are dominated by partially decayed and compressed organic material

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23
Q

main kinds of weathering

A
  1. chemical
  2. biological
  3. physical
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24
Q

chemical weathering is a result when

A

water or other substances chemically interact with the parent material

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25
Q

what conditions promote chemical weathering

A

warm, wet conditions

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26
Q

biological weathering

A

When living things break down parent material by physical or chemical means

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27
Q

example of biological weathering

A
  1. lichen
  2. trees and tree roots breaking apart rocks
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28
Q

physical weathering (mechanical)

A

Breaks rocks down without triggering a chemical change in the parent material

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29
Q

main agents of physical weathering

A
  1. temperature
  2. ice
  3. wind
  4. rain
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30
Q

a second process involved in soil formation (after weathering)

A

erosion

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31
Q

erosion

A

movement of particles from one location to another

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32
Q

agents of erosion

A
  1. wind
  2. water
  3. ice (glacier)
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33
Q

Sediment

A

The deposition of soil or regolith by wind, water or ice somewhere else

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34
Q

Horizon

A

Each distinct layer of soil developed through the movement of sediments after weathering

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35
Q

Soil profile

A

The cross-section of soil as a whole

36
Q

describe the leaching process

A

A process where materials suspended or dissolved in liquid are transported through the subsurface = its how materials are carried down through the soil

37
Q

what materials are the most commonly leached in soil

A

the ones that are the most soluble (easily dissolved)
- irons
- aluminum
- silicate minerals

38
Q

how does weathering and concentration of organic matter change down a soil profile

A

both decrease downwards in the profile

39
Q

Five major soil horizons

A

O Horizon
A Horizon
B Horizon
C Horizon
R Horzion

40
Q

O Horizon

A

The top layer of soil in some soil profiles
that is made up of organic matter, such as decomposing branches, leaves, crop residue, and animal waste

(collectively known as litter)

41
Q

A Horizon

A

Uppermost mineral horizon (AKA topsoil) that consists of inorganic mineral components with organic matter and humus from above mixed in

42
Q

permafrost in arctic soils

A

soils contain perennially (yearly) frozen layer

43
Q

topsoil

A

Portion of the soil that is most nutritive for plants = the most vital to ecosystems and agriculture = contains inorganic and organic material

44
Q

what soil horizon is home to the most organisms that give soil life

A

A Horizon

45
Q

B Horizon

A

Consists of minerals and organic matter that are leached from the topsoil and move downward where the deposited

Minerals can lead to the development of hard, mineral-rich layers depending on specific composition and structure

46
Q

what soil horizon is known as subsoil

A

B Horizon

47
Q

what is an issue associated with the B Horizon

A

hard, mineral layers can cause issues for plant growth

(Interfere with the drainage and prevent plant roots from penetrating lower, nutrient-rich soils)

48
Q

C horizon

A

A transition zone located below the B horizon that is not always present
but consists of broken-up parent material only slightly altered by processes of soil formation

49
Q

R horizon

A

Unaltered parent material

50
Q

properties used to classify soils

A
  1. colour (level of organic matter)
  2. texture (relative ease or difficulty to cultivate- lots of rocks, no rocks…)
  3. structure (clay, silt, sand)
  4. pH (ability to support plant growth)
51
Q

Ion exchange

A

positively charged particles (cations) and negatively charged particles (anions) are exchanged between the soil and the soil solution

52
Q

importance of cation exchange

A

process that allows plants to gain nutrients based on the negatively charged soils hold cations (magnesium, calcium, potassium)

53
Q

Cation exchange capacity

A

A measure of a soil’s ability to hold cations and preventing them from leaching away which makes them available to plants

54
Q

Greatest cation exchange capacity are found in soils

A
  • With fine texture
  • Rich in organic matter
55
Q

does cation exchange capacity increase or decrease as soil pH lowers (becomes acidic)

A

decreases = nutrients being leached away and instead supply plants with harmful aluminum ions

56
Q

importance of soil in nitrogen cycle (Nitrogen fixation vs nitrification vs denitrification)

A

Nitrogen fixation
- Nitrogen from the atmosphere is combined (fixed) with hydrogen to form ammonium to become available for plants

nitrification
- after nitrogen fixation, Ammonium ions are first converted into nitrite ions then into nitrate ions as nitrate ions can be taken up by plant roots as nutrients

denitrification
- When bacteria convert nitrates in soil or water into gaseous forms of nitrogen and completes the nitrogen cycle

57
Q

Main carbon fluxes in which soils are driven by

A
  1. photosynthesis
  2. production or organic matter
    (followed by respiration and decay of organic matter)
58
Q

what does the decay of soil organic matter produce

A

soil gases that contain carbon (carbon dioxide and methane)

59
Q

what is the largest terrestrial reservoir for carbon

A

soil

60
Q

high rainfall vs low rainfall on soil fertility

A

high rainfall
- leaches minerals and nutrients from topsoil away from plant’s roots

low rainfall
- leaching is reduced and nutrients remain high in the soil profile

61
Q

high(hotter) temps vs low (cooler) temps on soil fertility

A

higher temps
- speed the decomposition of leaf litter and uptake of nutrients from plants = topsoil remains thin

lower temps
- low the rate of decomposition of organic matter = more nutrients is left in the topsoil making richer topsoil

62
Q

Soil degradation

A

natural processes that damage to or loss of soil

63
Q

causes of soil degradation

A
  1. deforestation
  2. agriculture
  3. overgrazing
  4. industrial contamination (mining..)
64
Q

Deposition of sediments

A

The arrival of eroded material at its new location

65
Q

Accelerated erosion

A

erosion that takes place faster than soil is formed associated with human activity

66
Q

Three practices that have increased vulnerability of lands to erosion

A
  1. Overcultivation of fields through excessive ploughing or poor planning
  2. Overgrazing rangelands with more livestock than the land can support
  3. Clearing forested areas (especially on steep slopes)
67
Q

where is water erosion most likely

A

where slopes are steeper

68
Q

Chances of water erosion is increased by

A

○ Steeper slopes
○ Greater precipitation intensities
○ Sparser vegetation

69
Q

Land degradation

A

Change in soil health that results in the reduction or loss of biological or economic productivity of land caused by HUMAN ACTIVITIES

70
Q

Desertification

A

Natural process where formerly productive land becomes a desert because of climate change or prolonged drought

71
Q

Accelerated desertification

A

Type of land degradation that occurs in arid and semi-arid areas by HUMAN activities

72
Q

Crop rotation

A

The practice of alternating the kind of crop grown in a particular field from one season or year to the next

73
Q

benefits of crop rotation

A

Can return nutrients to the soil

break cycles of diseases associated with monoculture crops

minimize erosion

74
Q

Intercropping

A

Planting different types of crops in alternating bands or other spatially mixed arrangements

75
Q

benefit of intercropping

A

Slows erosion by providing more complete ground cover than a single crop

76
Q

agroforestry

A

When crops are interplanted with trees

77
Q

Shelterbelts act as

A

windbreaks (rows of trees or tall shrubs that are along edges of fields to slow the wind)

78
Q

Alley cropping is a combination of which soil conservation techniques

A

Combination of intercropping and shelterbelt practices

(Fields planted in rows of mixed crops are surrounded by or interspersed with rows of trees proving wood, fruit or protection from wind)

79
Q

Buffer zone

A

Consists of a strip around the edge or riparian zone of the water body which is planted with trees, shrubs or grasses

80
Q

benefits of buffer zones

A

Help stabilize eroding shorelines and create physical barrier between agricultural activities and sensitive aquatic areas

81
Q

is there such a thing as too much water when irrigating crops

A

YES - Soils too saturated with water can become waterlogged or salinization can happen

82
Q

what does soil mostly consist of

A

mineral matter with the rest being pore space occupied with air, water and gases

83
Q

parent material

A

the base geologic material of soil which determines the starting composition of soil

84
Q

what can be considered parent material

A
  • lava
    volcanic ash
    rock
    dunes
    bedrock
85
Q

5 factors that influence soil formation

A
  • climate
    (warm, wet climates = faster plant growth)
  • organisms
    (organisms that mix soils, add organic matter, affect soil’s composition and structure)
  • topography
    (land formations affect how soil and water move - steeper = more runoff and erosion)
  • parent material
    (parent material influence properties of the resulting soil)

-time
(soils form very slowly, four above factors change over time)

Environmental Science 2000 (10 decks)

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