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SSC 200 > Exam 2 Review > Flashcards

Exam 2 Review Flashcards

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
Q

The gravitational pull in macropores is stronger than adhesion so water drains freely. True or Flase?

A

True

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26
Q

Is the adhesion in micropores greater or weaker than gravity so water will be pulled into the pore?

A

Greater

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27
Q

What are the 3 major forces that affect soil water potential?

A

Matric, Osmotic, and Gravity

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28
Q

Gravity pulls water up. True or False

A

False

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29
Q

Gravitational Potential is positive. Matric and Osmotic are 0/negative. True or False?

A

True

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30
Q

Matric potential results from cohesion and adhesion. True or False?

A

True

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31
Q

Matric Potential

A

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.

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32
Q

Osmotic Potential

A

Mixture of water and dissolved solutes (inorganic salts/organic compounds), greater concentrate =negative water potential, important for water entering roots.

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33
Q

Saturation

A

Macro, meso and micropores are filled with water. Drains
due to gravity. No air.

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34
Q

Field Capacity

A

The amount of water
a soil can hold against the pull of gravity. Where gravitational water stops draining. Macropores emptied

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35
Q

Wilting Point

A

Water is held tight in the micropores. Adhesive forces are far greater than gravity

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36
Q

Hydroscopic Coefficient

A

Soil water
content of air-dried soil, which is soil
left out to dry at room temperature.

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37
Q

Oven Dry

A

Soil dried to have no water

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38
Q

Gravitation water

A

Water between saturation and field capacity

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39
Q

Plant-available water

A

Water between field capacity and permanent wilting point

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40
Q

Unavailable Water

A

Water between permanent wilting point and oven dry.

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41
Q

Coarse soils hold less water than fine-textured soils. True or False?

A

True

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42
Q

Clay soils

A

High water holding capacities due to the numerous small pores

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43
Q

Sandy soils

A

Low water holding capacity due to fewer micropores

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44
Q

Water movement follows water potential gradient no volumetric amounts. True or False?

A

True

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45
Q

Gypsum blocks

A

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
Q

Tensiometers

A

Measuring the tension of water due to adhesive forces with soil solids

47
Q

Time Domain Reflectometry (TDR)

A

Non-destructive method for measuring soil
moisture by using radar to transmit signals into soil and analyzing thee reflected signals.

48
Q

Structures Single Grain

A

Individual particles. Commonly found in sandy soils and C-horizon.

49
Q

Structureless Massive

A

No visible structure. Commonly found in C-horizons

50
Q

Platly

A

Flat plates. Commonly found in clayey soils and compared soils.

51
Q

Columnar

A

Vertical columns with a salt cap at the top. Commonly found in arid climates and subsoil.

52
Q

Prismatic

A

Vertical columns with sharp edges. Commonly found in subsoils with no/little salt accumulation.

53
Q

Blocky

A

Square like blacks with sharp edges. Commonly found in subsoils.

54
Q

Sub-angular Blocky

A

Square like blacks with rounded edges. Commonly found in subsoils.

55
Q

Granular

A

Cookie crumb, small (less than 0.5cm) peds. Commonly found in A-horizons.

56
Q

Red Colored Soil

A

Well drained

57
Q

Grey Colored Soil

A

Poorly drained (water logging)

58
Q

Infiltration

A

Is the entry of water into the soil from its surface.

59
Q

Sandy soils infiltrate water slower than clayey soils. True or Flase?

A

False

60
Q

What kind of movement do clayey soils have?

A

Horizontal

61
Q

What kind of movement do sandy soils have?

A

Lateral/Vertical

62
Q

Crop residues shade the soil and minimize the effect solar radiation on potential ET. True or False?

A

True

63
Q

Irrigation

A

What you do if you need to water plants. Changes with the season, time of day, and plant.

64
Q

Drainage

A

What you do if you have too much water. Can improve gas exchange.

65
Q

Aeration

A

What you do if you need to improve gas exchange between soil and atmosphere.

66
Q

Condensation

A

The process of water changing from a vapor to a liquid.

67
Q

Infiltration

A

A portion of the precipitation that reaches the Earth’s surface seeps into the ground.

68
Q

Runoff

A

Precipitation that reaches the surface of the Earth but does not infiltrate.

69
Q

Evaporation

A

Water turning from liquid to gas form.

70
Q

Transpiration

A

Plants take in water through the roots and release it through the
leaves. Plant sweat.

71
Q

Evapotranspiration

A

The cumulative loss of vapor to the atmosphere from
evaporation and transpiration.

72
Q

Detachment

A

Individual
particles are loosened
from the soil mass (rain
splash, flowing water,
wind).

73
Q

Transport

A

Water or wind carries the
detached particles
downslope or downwind.

74
Q

Deposition

A

Detached
particles are deposited in
places of a lower
elevation.

75
Q

Types of Erosion

A

Sheet, Rill, Gully

76
Q

What soil separate has the largest surface area?

A

Clay

77
Q

What soil separate would have a particular diameter of 0.2mm?

A

Sand

78
Q

What is the texture of a soil with 40% sand and 20% clay?

A

Loam

79
Q

A soil with 55% silt will always be classified as?

A

Cannot be determined

80
Q

What soil structure is common in sandy soils?

A

Structureless single grain

81
Q

What soil structure is commonly found in the A-horizon

A

Granular

82
Q

The grey color of soil can indicate that the soil has iron and is not well drained. True or False?

A

True

83
Q

Compaction will decrease the bulk density of a soil. True or False?

A

False

84
Q

A soil bulk density increase, the porosity of the soil increases. True or False?

A

False

85
Q

What that plants uptake and release back into the atmosphere is called?

A

Transpiration

86
Q

The force between 2 water molecules is called ____, while the force between a water molecule and soil particle is called ____.

A

Cohesion, Adhesion

87
Q

When the force of gravity is smaller than the force of adhesion, the water will stay in the soil. True or False?

A

True

88
Q

What force results from cohesion and adhesion and is a negative force?

A

Matric

89
Q

What soil texture can hold the most water?

A

Silty clay

90
Q

What water freely drains in the soil and is responsible for a lot of leaching of nutrients from soil?

A

Gravitational

91
Q

Wilting point is characterized by:

A

The amount of water tightly held to soil particles

92
Q

What pore size is plant-available water held in?

A

Mesopores

93
Q

How is soil water content estimated in soil?

A

Tensiometer

94
Q

What soil will infiltrate the greatest amount of water?

A

Beach sand

95
Q

A soil has a platy texture, lots of micropores, and has a slow infiltration rate. What is the soil texture?

A

Clayey

96
Q

Drainage systems are designed to increase gas exchange between the soil and atmosphere, so the soil can get more CO2. True or False?

A

False

97
Q

What soil particle size is the most easily eroded?

A

Silt

98
Q

What practice will reduce erosion by 90%?

A

Adding organic matter

99
Q

Groundcovers reduce soil erosion by stopping which part of soil erosion?

A

Detachment

100
Q

Can you describe the Texture by Feel method?

A

Is it sticky, gritty, can it be made into a ribbion?

101
Q

What effect does soil organic matter have on color?

A

It makes it darker

102
Q

What is the formula for bulk density?

A

Bulk Density = Mass of Oven Dry Soil (g) / Volume of Soil (cm3)

103
Q

What is the formula for Particle Density?

A

Particle Density = Mass of Oven Dry Soil (g) / Volume of Particles (cm3)

104
Q

What is the formula for Porosity?

A

Porosity = Volume of Pores (cm3) / Volume of Soil (cm3)

105
Q

What is the alternate formula for Porosity?

A

Porosity = 1- Bulk Density / Particle Density

106
Q

To determine the bulk density of and undisturbed soil core, one must know its oven-dry weight and ______.

A

Total Volume

107
Q

Brown and red colors in subsurface horizons are caused by _____ in the soil.

A

Clay iron oxides

108
Q

In _____ textured soils, nutrient leaching is a concern because of low cation exchange capacities.

A

Coarse

109
Q

A tensiometer provides a measure of _______.

A

Soil matrix potential

110
Q

Which soil structure type would you expect to fine in an A horizon of a soil formed in a humid environment?

A

Granular

111
Q
A

SSC 200 (2 decks)

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