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SSC 200 > Exam 2 Review > Flashcards

Exam 2 Review Flashcards

(111 cards)

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1
Q

Bulk Density

A

Mass of a volume of undisturbed oven dry soil. A mass divided by a volume

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2
Q

Sandy soils have a higher bulk density than clayey soils. True or False?

A

True

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3
Q

Clayey soils have a higher bulk density than organic soils. True or False?

A

True

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4
Q

Porosity

A

total pore space or a measure of the soil volume that hold air and water

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5
Q

Porosity and bulk density are inversely related. Porosity increases as bulk density decreases. True or False?

A

True

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6
Q

Do clayey soils have more or less pore space than sandy soils?

A

More

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7
Q

To improve porosity long-term you should add what?

A

Organic matter

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8
Q

A soil sample was collected in a cylinder that has a diameter of 10 cm and a height of 20
cm. The saturated weight of the soil is 2,000 g and the oven dry weight is 1,650 g. The
volume of a cylinder is 𝑉 = 𝜋𝑟
2 × ℎ

A

What is the volume and bulk density of the soil?

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9
Q

Soil texture

A

Describes the distribution of particles into different size classes less than 2 mm and the divided into sand, silt, and clay.

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10
Q

Gravel

A

Greater than 2mm

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11
Q

Sand

A

2-0.05mm

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12
Q

Silt

A

0.05-0.002mm

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13
Q

Clay

A

Less than 0.002mm

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14
Q

Does the increase of clay increase the surface area?

A

Yes

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15
Q

Block-like particles have more surface area than plate-like particles. True or False.

A

Flase

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16
Q

What is used to measure soil texture in the lab?

A

A hydrometer

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17
Q

Coarse textured soils

A

Rapidly drains water, feels gritty, poor nutrient, low organic matter.

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18
Q

Fine textured soils

A

Water drains slowly, feels sticky, higher fertility and organic matter.

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19
Q

Cohesion

A

The attraction of water molecules for each other primarily due to hydrogen bonding.

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20
Q

Adhesion

A

The attraction of water molecules for soil surfaces. Water adsorption to the surface of soil via H-bonding.

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21
Q

Macropores

A

Large pores, water drains rapidly through them due to the force of gravity.

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22
Q

Micropores

A

Small pores, tend to retain water so tightly, its unavailable to plants.

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23
Q

Mesopores

A

Medium-sized pores, will find more plant-available water. Held tighter than the force of gravity but not so tight that plant can’t extract the water.

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24
Q

Capillarity

A

The movement of water up a wick made of hydrophilic solid materials.

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25
The gravitational pull in macropores is stronger than adhesion so water drains freely. True or Flase?
True
26
Is the adhesion in micropores greater or weaker than gravity so water will be pulled into the pore?
Greater
27
What are the 3 major forces that affect soil water potential?
Matric, Osmotic, and Gravity
28
Gravity pulls water up. True or False
False
29
Gravitational Potential is positive. Matric and Osmotic are 0/negative. True or False?
True
30
Matric potential results from cohesion and adhesion. True or False?
True
31
Matric Potential
Results in negative potential, affected by differences in adhesion, greatest effect of release of water, as soil dries it decreases from 0 to a negative number.
32
Osmotic Potential
Mixture of water and dissolved solutes (inorganic salts/organic compounds), greater concentrate =negative water potential, important for water entering roots.
33
Saturation
Macro, meso and micropores are filled with water. Drains due to gravity. No air.
34
Field Capacity
The amount of water a soil can hold against the pull of gravity. Where gravitational water stops draining. Macropores emptied
35
Wilting Point
Water is held tight in the micropores. Adhesive forces are far greater than gravity
36
Hydroscopic Coefficient
Soil water content of air-dried soil, which is soil left out to dry at room temperature.
37
Oven Dry
Soil dried to have no water
38
Gravitation water
Water between saturation and field capacity
39
Plant-available water
Water between field capacity and permanent wilting point
40
Unavailable Water
Water between permanent wilting point and oven dry.
41
Coarse soils hold less water than fine-textured soils. True or False?
True
42
Clay soils
High water holding capacities due to the numerous small pores
43
Sandy soils
Low water holding capacity due to fewer micropores
44
Water movement follows water potential gradient no volumetric amounts. True or False?
True
45
Gypsum blocks
The resistance of electrodes embedded in a porous block is proportional to its water content. The wetter a block is, the lower the resistance measured across two embedded electrodes.
46
Tensiometers
Measuring the tension of water due to adhesive forces with soil solids
47
Time Domain Reflectometry (TDR)
Non-destructive method for measuring soil moisture by using radar to transmit signals into soil and analyzing thee reflected signals.
48
Structures Single Grain
Individual particles. Commonly found in sandy soils and C-horizon.
49
Structureless Massive
No visible structure. Commonly found in C-horizons
50
Platly
Flat plates. Commonly found in clayey soils and compared soils.
51
Columnar
Vertical columns with a salt cap at the top. Commonly found in arid climates and subsoil.
52
Prismatic
Vertical columns with sharp edges. Commonly found in subsoils with no/little salt accumulation.
53
Blocky
Square like blacks with sharp edges. Commonly found in subsoils.
54
Sub-angular Blocky
Square like blacks with rounded edges. Commonly found in subsoils.
55
Granular
Cookie crumb, small (less than 0.5cm) peds. Commonly found in A-horizons.
56
Red Colored Soil
Well drained
57
Grey Colored Soil
Poorly drained (water logging)
58
Infiltration
Is the entry of water into the soil from its surface.
59
Sandy soils infiltrate water slower than clayey soils. True or Flase?
False
60
What kind of movement do clayey soils have?
Horizontal
61
What kind of movement do sandy soils have?
Lateral/Vertical
62
Crop residues shade the soil and minimize the effect solar radiation on potential ET. True or False?
True
63
Irrigation
What you do if you need to water plants. Changes with the season, time of day, and plant.
64
Drainage
What you do if you have too much water. Can improve gas exchange.
65
Aeration
What you do if you need to improve gas exchange between soil and atmosphere.
66
Condensation
The process of water changing from a vapor to a liquid.
67
Infiltration
A portion of the precipitation that reaches the Earth's surface seeps into the ground.
68
Runoff
Precipitation that reaches the surface of the Earth but does not infiltrate.
69
Evaporation
Water turning from liquid to gas form.
70
Transpiration
Plants take in water through the roots and release it through the leaves. Plant sweat.
71
Evapotranspiration
The cumulative loss of vapor to the atmosphere from evaporation and transpiration.
72
Detachment
Individual particles are loosened from the soil mass (rain splash, flowing water, wind).
73
Transport
Water or wind carries the detached particles downslope or downwind.
74
Deposition
Detached particles are deposited in places of a lower elevation.
75
Types of Erosion
Sheet, Rill, Gully
76
What soil separate has the largest surface area?
Clay
77
What soil separate would have a particular diameter of 0.2mm?
Sand
78
What is the texture of a soil with 40% sand and 20% clay?
Loam
79
A soil with 55% silt will always be classified as?
Cannot be determined
80
What soil structure is common in sandy soils?
Structureless single grain
81
What soil structure is commonly found in the A-horizon
Granular
82
The grey color of soil can indicate that the soil has iron and is not well drained. True or False?
True
83
Compaction will decrease the bulk density of a soil. True or False?
False
84
A soil bulk density increase, the porosity of the soil increases. True or False?
False
85
What that plants uptake and release back into the atmosphere is called?
Transpiration
86
The force between 2 water molecules is called ____, while the force between a water molecule and soil particle is called ____.
Cohesion, Adhesion
87
When the force of gravity is smaller than the force of adhesion, the water will stay in the soil. True or False?
True
88
What force results from cohesion and adhesion and is a negative force?
Matric
89
What soil texture can hold the most water?
Silty clay
90
What water freely drains in the soil and is responsible for a lot of leaching of nutrients from soil?
Gravitational
91
Wilting point is characterized by:
The amount of water tightly held to soil particles
92
What pore size is plant-available water held in?
Mesopores
93
How is soil water content estimated in soil?
Tensiometer
94
What soil will infiltrate the greatest amount of water?
Beach sand
95
A soil has a platy texture, lots of micropores, and has a slow infiltration rate. What is the soil texture?
Clayey
96
Drainage systems are designed to increase gas exchange between the soil and atmosphere, so the soil can get more CO2. True or False?
False
97
What soil particle size is the most easily eroded?
Silt
98
What practice will reduce erosion by 90%?
Adding organic matter
99
Groundcovers reduce soil erosion by stopping which part of soil erosion?
Detachment
100
Can you describe the Texture by Feel method?
Is it sticky, gritty, can it be made into a ribbion?
101
What effect does soil organic matter have on color?
It makes it darker
102
What is the formula for bulk density?
Bulk Density = Mass of Oven Dry Soil (g) / Volume of Soil (cm3)
103
What is the formula for Particle Density?
Particle Density = Mass of Oven Dry Soil (g) / Volume of Particles (cm3)
104
What is the formula for Porosity?
Porosity = Volume of Pores (cm3) / Volume of Soil (cm3)
105
What is the alternate formula for Porosity?
Porosity = 1- Bulk Density / Particle Density
106
To determine the bulk density of and undisturbed soil core, one must know its oven-dry weight and ______.
Total Volume
107
Brown and red colors in subsurface horizons are caused by _____ in the soil.
Clay iron oxides
108
In _____ textured soils, nutrient leaching is a concern because of low cation exchange capacities.
Coarse
109
A tensiometer provides a measure of _______.
Soil matrix potential
110
Which soil structure type would you expect to fine in an A horizon of a soil formed in a humid environment?
Granular
111

SSC 200 (2 decks)

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