Soil and Soil Resources Flashcards
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)
2
Q
what are some biotic communities in soil
A
- microorganisms
- larger organisms (earthworms, burrowing mammals, amphibians and reptiles)
3
Q
how does soil formation begin
A
with the breakdown of parent rock by weathering (exposure to atmosphere, hydrosphere and biosphere)
4
Q
what do soil profiles consists of
A
distinct layers (horizons)
5
Q
why do soil profiles form
A
a result of weathering combined with leaching
6
Q
why is soil crucial in supporting life
A
they are crucial for providing nutrients for plant growth which support life
7
Q
how do materials for plant growth move from soil to soil solution and back
A
through ion exchange
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
9
Q
main mechanisms of soil loss
A
- water erosion
wind erosion (aeolian erosion)
10
Q
is desertification a natural process or artificial process
A
natural process
11
Q
is accelerated erosion a natural process or artificial process
A
artificial - caused by human activities
12
Q
what are some (agricultural) ways to protect soils from erosion
A
- crop rotation
- contour farming
- intercropping
- terracing
- shelterbelts and buffer zones
- reduced tillage
13
Q
what can overirrigation cause
A
salinization and waterlogging
14
Q
how does overirrigation affect crop yields
A
lower crop yields
15
Q
how does overgrazing affect soils
A
causes soil compaction and degradation
16
Q
why is it important to preserve grasses on rangelands
A
to protect soils from the effects of overgrazing
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
18
Q
what is the most common parent material for soil
A
bedrock (the continuous mass of solid rock comprising earth’s crust)
19
Q
weathering
A
The physical, chemical and biological processes that break down rocks and minerals
20
Q
humus
A
Dark, spongy, crumbly mass of material made of up complex organic compounds
21
Q
describe soil with high humus content
A
hold more moisture and are more productive for plant life
22
Q
peat
A
Soils that are dominated by partially decayed and compressed organic material
23
Q
main kinds of weathering
A
- chemical
- biological
- physical
24
Q
chemical weathering is a result when
A
water or other substances chemically interact with the parent material
25
what conditions promote chemical weathering
warm, wet conditions
26
biological weathering
When living things break down parent material by physical or chemical means
27
example of biological weathering
1. lichen
2. trees and tree roots breaking apart rocks
28
physical weathering (mechanical)
Breaks rocks down without triggering a chemical change in the parent material
29
main agents of physical weathering
1. temperature
2. ice
3. wind
4. rain
30
a second process involved in soil formation (after weathering)
erosion
31
erosion
movement of particles from one location to another
32
agents of erosion
1. wind
2. water
3. ice (glacier)
33
Sediment
The deposition of soil or regolith by wind, water or ice somewhere else
34
Horizon
Each distinct layer of soil developed through the movement of sediments after weathering
35
Soil profile
The cross-section of soil as a whole
36
describe the leaching process
A process where materials suspended or dissolved in liquid are transported through the subsurface = its how materials are carried down through the soil
37
what materials are the most commonly leached in soil
the ones that are the most soluble (easily dissolved)
- irons
- aluminum
- silicate minerals
38
how does weathering and concentration of organic matter change down a soil profile
both decrease downwards in the profile
39
Five major soil horizons
O Horizon
A Horizon
B Horizon
C Horizon
R Horzion
40
O Horizon
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
A Horizon
Uppermost mineral horizon (AKA topsoil) that consists of inorganic mineral components with organic matter and humus from above mixed in
42
permafrost in arctic soils
soils contain perennially (yearly) frozen layer
43
topsoil
Portion of the soil that is most nutritive for plants = the most vital to ecosystems and agriculture = contains inorganic and organic material
44
what soil horizon is home to the most organisms that give soil life
A Horizon
45
B Horizon
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
what soil horizon is known as subsoil
B Horizon
47
what is an issue associated with the B Horizon
hard, mineral layers can cause issues for plant growth
(Interfere with the drainage and prevent plant roots from penetrating lower, nutrient-rich soils)
48
C horizon
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
R horizon
Unaltered parent material
50
properties used to classify soils
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
Ion exchange
positively charged particles (cations) and negatively charged particles (anions) are exchanged between the soil and the soil solution
52
importance of cation exchange
process that allows plants to gain nutrients based on the negatively charged soils hold cations (magnesium, calcium, potassium)
53
Cation exchange capacity
A measure of a soil's ability to hold cations and preventing them from leaching away which makes them available to plants
54
Greatest cation exchange capacity are found in soils
- With fine texture
- Rich in organic matter
55
does cation exchange capacity increase or decrease as soil pH lowers (becomes acidic)
decreases = nutrients being leached away and instead supply plants with harmful aluminum ions
56
importance of soil in nitrogen cycle (Nitrogen fixation vs nitrification vs denitrification)
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
Main carbon fluxes in which soils are driven by
1. photosynthesis
2. production or organic matter
(followed by respiration and decay of organic matter)
58
what does the decay of soil organic matter produce
soil gases that contain carbon (carbon dioxide and methane)
59
what is the largest terrestrial reservoir for carbon
soil
60
high rainfall vs low rainfall on soil fertility
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
high(hotter) temps vs low (cooler) temps on soil fertility
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
Soil degradation
natural processes that damage to or loss of soil
63
causes of soil degradation
1. deforestation
2. agriculture
3. overgrazing
4. industrial contamination (mining..)
64
Deposition of sediments
The arrival of eroded material at its new location
65
Accelerated erosion
erosion that takes place faster than soil is formed associated with human activity
66
Three practices that have increased vulnerability of lands to erosion
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
where is water erosion most likely
where slopes are steeper
68
Chances of water erosion is increased by
○ Steeper slopes
○ Greater precipitation intensities
○ Sparser vegetation
69
Land degradation
Change in soil health that results in the reduction or loss of biological or economic productivity of land caused by HUMAN ACTIVITIES
70
Desertification
Natural process where formerly productive land becomes a desert because of climate change or prolonged drought
71
Accelerated desertification
Type of land degradation that occurs in arid and semi-arid areas by HUMAN activities
72
Crop rotation
The practice of alternating the kind of crop grown in a particular field from one season or year to the next
73
benefits of crop rotation
Can return nutrients to the soil
break cycles of diseases associated with monoculture crops
minimize erosion
74
Intercropping
Planting different types of crops in alternating bands or other spatially mixed arrangements
75
benefit of intercropping
Slows erosion by providing more complete ground cover than a single crop
76
agroforestry
When crops are interplanted with trees
77
Shelterbelts act as
windbreaks (rows of trees or tall shrubs that are along edges of fields to slow the wind)
78
Alley cropping is a combination of which soil conservation techniques
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
Buffer zone
Consists of a strip around the edge or riparian zone of the water body which is planted with trees, shrubs or grasses
80
benefits of buffer zones
Help stabilize eroding shorelines and create physical barrier between agricultural activities and sensitive aquatic areas
81
is there such a thing as too much water when irrigating crops
YES - Soils too saturated with water can become waterlogged or salinization can happen
82
what does soil mostly consist of
mineral matter with the rest being pore space occupied with air, water and gases
83
parent material
the base geologic material of soil which determines the starting composition of soil
84
what can be considered parent material
- lava
volcanic ash
rock
dunes
bedrock
85
5 factors that influence soil formation
- 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)
