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Soil Science > Test 2 > Flashcards

Test 2 Flashcards

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1
Q

Percent of water that’s ocean water.
Ice?
all other water?
ground water?

A

97.25%
2%
<0.05%
0.7%

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2
Q

percent lake water?
Soil moisture?
Atmosphere?
Rivers

A

60%
33%
6%
1%

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3
Q

What are two restrictions of water movement?

A

Rate of water supply from soil to root.

Rate of loss from leaves through evaporation.

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4
Q

Evapotranspiration is affected by?(5)

A 
Radiant energy- 540 calories to evaporate 1g water.
Atmospheric vapor pressure
Temperature
wind
soil moisture supply
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5
Q

Different crops lose moisture at different rates(T/F)

A

True

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6
Q

Transpiration ratio-

A

kg of water needed to produce 1kg of dry weight.

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7
Q

Water vapor losses from soil surface and plants are determined by(4)

A

Climate
Plant cover
Water use efficiency
Length and season of plant growing period

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8
Q

Ways to control soil evaporation?

A

Encourage soil cover
Mulches
Paper plastic mulches- high cost/high value crops
crop residue and conservation tillage- requires herbicide use.

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9
Q

Percolation-

A

subsurface drainage, downward movement of water through soil.
-loss of soluable salts

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10
Q

runoff-

A

surface drainage

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11
Q

Leaching losses

A

loss of fertilizer
soil and water pollution
problems abated through split applications of fertilizers.

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12
Q

infiltration-

A

absorption of water by soil

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13
Q

If rate of rainfall exceeds rate of infiltration what happens?

A

soil ponding or surface runoff occurs.

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14
Q

Land drainage occurs in what two regions?

A

Delta and flat coastal plains.

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15
Q

Ex. of subsurface drains?(3)

A

Mole drain-lasts one season
Perforated plastic pipe- 90% of todays systems
Clay tile drains- to expensive for ag. popular 20-30 years.

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16
Q

Benefits of drainage?(5)

A 
reduces frost brewing
helps soils warm up faster in spring
Aeration
easier to work fields
Maintains productivity of irrigated soils.(no salting out)
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17
Q

Perc test is used for what? how do you do one?

A

to determine percolation test. and determine solubility for a septic tank drainfield.
measure water in a hole over time.

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18
Q

Aeration-

A

process of maintaining a supply of O2 to the soil

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19
Q

Oxygen is important why?

A

respiration
organic matter decay
release organic nutrients(N,F,S)
reducing toxicities of elements( Mn and S)

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20
Q

Diffusion-

A

random motion of molecules from an area of high concentration to an area of low concentration.

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21
Q

Partial pressure-

A

the pressure a gas would exert if it alone were present in volume occupied by a mix.

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22
Q

Factors affecting diffusion-

A

Texture-
Structure-
Water Content-

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23
Q

Texture-

A

finer textures soils have more micropores

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24
Q

Structure-

A

introduces large pores into fine textured materials.

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25
Q

Water Content-

A

drainage of macropores, oxygen diffuses more slowly through water than air.

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26
Q

Consequences of poor aeration(5)

A 
reduces microbial activity
Accumulation of organic acids
Plant growth curtailed
Absorption of nutrients and water is decreased
Toxic compounds
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27
Q

Poor aeration-

A

if air filled porosity <20% plants will suffer from deterioration of roots.

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28
Q

Wetlands-

A

Soils that are water-saturated near the surface for long periods of time. Plants and microbes can grow and remove oxygen.

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29
Q

The weter end of a wet land is where?

A

where water is to deep for rooted emergent vegetation.

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30
Q

Wetland Delineation-

A

the drier end of wetland.

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31
Q

3 characteristics of a wetland-

A

Wetland hydrology, Hydric soils, Hydrophytic plants

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32
Q

Hydric soils-

A

soils subjected to periods of saturation

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33
Q

Soil temperature influences:

A

Microorganisms- o matter, decomposition
Plants- germination, nutrient uptake,transpiration/respiration.
Mineral weathering

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34
Q 
Reflectance by clouds-
absorbence by dust and water-
Evaporation-
Radiation-
Reflection-
A 
30%
20%
30%
5%
5%
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35
Q

what 10% of sun is absorbed by the soil?

A

10%

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36
Q

factors that affect energy entering the soil?

A

soil color
slope- closer to perpendicular the greater the absorption
Vegetation

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37
Q

Daily temperature fluctuations are greatest at the soil surface and decrease with debth.(T/F)

A

true.

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38
Q

How can you modify soil temp?

A

Moisture/Drainage

Mulches(color)

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39
Q

What is the smallest soil particle?

A

Clay 1um, highly reactive w/ large surface area per unit mass.

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40
Q

CEC-

A

ions are absorbed on the colloid surfaces.

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41
Q

Mineral properties-(2)

A

Composition-kinds of atoms

Crystallinity- arrangement

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42
Q

clays are composed of two basic crystal units:

A

Tetrahedrons

Octahedrons

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43
Q

Interlocking units of Aluminum Octrahedron form what?

A

an octrahedral sheet.

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44
Q

what is an isomorphic substitution?

A

substitution of an ion of similar size for Si or Al that occur during crystal formations. has charge imbalance but isnt negative.

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45
Q

1:1 Clay minerals are made of?

A

1 tetrahedral sheet and 1octohedral sheet, share oxygen atoms. H-bonds

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46
Q

2:1 Clay minerals are made of?

A

1 octohedral and 2 tetrahedral sheets, share oxygen linked sheets.

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47
Q

Kandites

A

1:1 Clay mineral
CEC 2-10 cmolc low reactivity
broken edges, non explanding.

48
Q

Smectite-

A

2:1
CEC 80-120 cmolc
highly reactive, explanding, high surface area

49
Q

illite-

A

2:1

CEC is 20-40 medium

50
Q

vermiculite-

A

similar to illite

CEC 120-150,limited expanding,high surface area.

51
Q

Chlorite-

A

2:1:1

CEC 20-40, medium ,increased strength of bonding.

52
Q

other sources of charges in soil:(3)

A

Exposed crystal edges
Fe and Al oxides
Humus

53
Q

Cations-

A

positively charged ions

54
Q

Clays-

A

negativly charge

55
Q

Cation adsorption-

A

electrostatic attraction, not readily leached

56
Q

Cation exchange-

A

replacement of one cation for another on the exchange site.

57
Q

CEC definition-

A

ability of soil to hold and exchange cations, measure of the basic fertility status of the soil

58
Q

Mole-

A

6.02x10^23 ions, mass of 1 mole of an ion

59
Q

equivalent-

A

quantity of an ion that will supply the same total charge as 1 mole of H+

60
Q

Predominant cations

A 
Ca+2
Mg+2
H+
Na+
K+
Al+3
61
Q

factors influencing exchange reactions-(4)

A

Concentration of ions
Number of charges on ions
Hydrated radius of ions
pH

62
Q

pH-

A

master variable that affects many soil chemical and biological properties.

63
Q

Why is pH important?

A

Availability of nutrients
plant species that will grow
Activity of soil microorganisms
Mobility and breakdown of pollutants

64
Q

An Acid donates what? and A base excepts what?

A

protons(H+) and a Base accepts the proton(H+)

65
Q

What is the end result of an acid and base combining?

A

formation of water and a salt.

66
Q

pH is the unit of measure for what?

A

acidity and alkalinity

67
Q

Buffer-

A

a substance that has the ability to resist changes in pH, acts as a reserve and soil systems are natural buffers.

68
Q

Soil solution(Active Acidity)-

A

1 of every 10,000 exchangable cations are in active phase. less than 1 lb/acre of lime needed to neutralize.

69
Q

Soil Colloids”reserve acidity”-

A

2-8 tons /acre needed to neutralize .

70
Q

Salt replacable(exchangable) acidity-

A

involves Al and H that are easily exchangeable by other cations in a simple unbuffered salt solution.

71
Q

Residual Activity-

A

Can be neutralized by limestone or other alkaline materials but cannot be detected by the salt- replaceable technique.

72
Q

How do soil become acidic?

A

Leaching of bases by water
Crop removal of bases
Acid forming fertilizers

73
Q

Effects of soil pH on plant growth:(4)

A

Nutrient avalibility
Solubulity of toxic substances
effects on microorganisms
Direct effect of pH on root cells

74
Q

Percents of base saturation 6.5-7:
5.5-6.5:
low-5.5:

A

80% and up
50-80%|
less than 50%

75
Q

Liming soils:

A

raises pH and eliminates nutrient toxicities, deficiences and microbial activity. soils respond to lime after the pH drops below 6.0

76
Q

Soil amendment-

A

anything added to the soil that improves soil chemistry without providing nutrition. ex.(lime)

77
Q

How does lime work?

A

it breaks down Ca ions and Carbonic acid.neutralizing acidity.

78
Q

Limiting agents:

A

CaO
Ca(OH)2
CaCO3
MgCO3

79
Q

Application of lime-

A

every 3 -5 years
applied with or before the crop
not economical to apply >6tons/acre/year
Amount based on soils buffering capacity

80
Q

Limestone quality depend on?

A

the neutralization value and fitness of grind, limstone quality is the product of the neutraliztion value and the fitness factor.

81
Q

Fitness Factor-

A

depends on how finely the rock material is ground. smaller particles the more reactive,

82
Q

Quality factor-

A

Neutralizing value X fitness factor

83
Q

Acid rain-

A

Acid decomposition from the atmosphere. Nitrogen and sulfur containing gases. mostly a problem in humid forests near urbanized and industrialized areas.

84
Q

How to reduce the effects of acid rain(3)

A

reduce S and N emissions
liming lakes and forests is economically limited
re-vegetation.

85
Q

What is capable of acting as a habitat for biological organisms?

A

Soil

86
Q

What is responsible for most of the chemistry that occurs in soil?

A

Soil organisms

87
Q

Photosynthesis

A

6CO2+6H2O =C6H12O6 +O2

88
Q

Respiration

A

C6H12O6+6O2=6CO2+6H2O

89
Q

Soil macro and micro organisms are important for:(4)

A

Organic matter decomposition
Nutrient availability
Soil development
Plant disease

90
Q

Prokaryotes:

A

Bacteria

91
Q

How do large animals help soil develop-

A

enhance soil by burrowing and mixing soil

92
Q

Earthworms

A

Annelida
excret casts
increase aeration and drainage
increase size and stability of soil aggregates
mixing is very important in no till system

93
Q

Protozoa

A

most varied and numberous
cause animal and human disease
predators in the rhizosphere

94
Q

Nematodes-

A

Microscopic thread worms or eelworms

95
Q

Saprophytes-

A

organisms that live on decaying matter

96
Q

Parasites-

A

infest roots causeing extensive damage to field and vegetable crops

97
Q

predators-

A

prey on other microbes

98
Q

Green plants-(3)

A

Vascular plant,
contribute to soil more than other living organisms combined
autotrophs

99
Q

Soil benefits of plants-(4)

A

Organic matter produced when plants decompose
Root channels influence physical properties
Nutrient uptake influences soil chemistry
root decomposes influences soil organisms

100
Q

roots-(rhizoshpere)

A

tiny channels are increased in size as roots swell and grow, 15-40% mass of above ground biomass.

101
Q

rhizosphere contributes to:(4)

A

organic acids
amino acids and simple sugars
Mucigel
competition for resources.

102
Q

Algae-

A

photosynthetic,aerobic photoautotrophs.

needs oxygen light and moisture.

103
Q

Fungi-

A

Aerobic heterotrophs, humus formation
need oxygen and organic carbon
responsible for most soil born diseases

104
Q

Molds-

A

organisms of threadlike mats formed from individual strands, break down anything, low pH

105
Q

Mycorrhizae-

A

symbiotic mold fungi,
fungus root symbiosis obtain c energy from roots,
act as root hairs
help supply nutrients to root.

106
Q

Ectomycorrhizae-

A

external, doesn not penetrate the cortex cell walls of the root.

107
Q

Endomycorrhizae-

A

enter cells

108
Q

Actinomycetes-

A

resemble molds, like pH OF 6.5-7,

Can break down complex substances.

109
Q

Bacteria-

A

smallest organisms,
most diversity
unicellular form colonies or spores

110
Q

Autotrophs-

A

C form CO2 ,inorganic

111
Q

Heterotrophs-

A

C and energy from .

most bacteria.(ultimate decomposers)

112
Q

injurious effects of soil organisms:

A

rodents eat roots
everything else eats plants
soil born diseases, most from fungi

113
Q

Controls of plant diseases:(6)

A 
Quarantine
Eliminate crop host
Crop rotation or tillage
pH control
Steam and chemical sterilization
Plant breeding
114
Q

Agriculture practices that decrease diversity:(5)

A 
pesticides
erosion
monocultures
excess tillage
industrial sewage
115
Q

Aig practices that increase diversity:(5)

A 
Drainage and aeration
Fert and lime
manures
balanced irrigation
Erosion control

Soil Science (3 decks)

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