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Exam Two Flashcards

(90 cards)

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1
Q

How do we determine pH?

A

H+ and OH- ions.
More H+ is acidic
More OH is alkaline

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2
Q

How does pH affect plants in soil?

A

Determines which plants dominate
What crops can grow
High acidity = more aggregate stability

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3
Q

How does acidity affect pollutants?

A

Acidic: lets pollutants pass through
Alkaline: holds pollutants

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4
Q

How does humidity affect acidity?

A

H+ binds to soils better than OH-, so water in humid environments is able to wash away negatively charged OH-

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5
Q

What pH is best for plants? Why?

A

7, charges soil locks nutrients

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6
Q

How do carbonic acids release H+ in soil?

A

CO2 dissolves in water, H+ is removed by water

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7
Q

Oxidation of what elements adds H+ to soil?

A

Nitrogen and sulfur

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8
Q
A
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9
Q

How does precipitation affect pH

A

Raindrops pick up CO2 in the air and lower pH (more acidic)

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10
Q

How do plants add H+ into soil?

A

Plants exude H+ in order to maintain balance of cation/anions internally
Plants release H+ to gain access to cations in soil

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11
Q

How does acidity affect available plant nutrients?

A

Acidic soils deficient in everything but iron, manganese, zinc
Alkaline soils deficient in manganese, zinc, copper, boron

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12
Q

What is aluminum toxcitiy? What soils does it occur in?

A

H+ attacks Al and released Al3+.
Al3+ cannot be exchanged at caiton exchange sites, so other nutrients are washed out.
Found in acid soils

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13
Q

What are acid cations?

A

Al3+ and H+

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14
Q

How can we reduce soil pH

A

Adding OM, adding elemental sulfur, adding ferrous sulfate

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15
Q

How can we increase soil pH

A

Adding lime

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16
Q

Describe polarity

A

Water has 2 charges. H is positive and O is negative

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17
Q

Why does clay hold water better than sand?

A

Capillary action: cohesion + adhesion allow water to move through soil in different directions

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18
Q

Describe hydrogen bonding

A

Positive H is attracted to another negative O, so water molecules are attracted to eachother. Weak bond

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19
Q

How does co/adhesion affect soils

A

Solids in soils retain water + control its movement
Allows plasticity

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20
Q

How does water potential affect soils?

A

Determines direction and rate of water movement in soils. Its why i can put a pot in a bowl of water to hydrate it :)

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21
Q

How do water relations tie into one another?

A

Polarity => hydrogen bonds => cohesion => surface tension.
Surface tension + adhesion => capillary action

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22
Q

Describe water and soil particles in different hydration levels

A

Wet soil: water in large pores or thick films = available
Dry soil: water in tight, thin films = wilting point

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23
Q

Define field capacity

A

Water is being held loosely by the soil due to an excess in water

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24
Q

Define wilting point

A

Point of dryness where water is being held so tightly by the soil, plants cannot use it. No turgid potential

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25
Define turgidity
Ability of a plant to support its own weight Turgid potential: pressure against plants cell wall
26
How do we measure salinity?
TDS in ppm Electrical conductivity in deciSemens/meter
27
How does electrical conductivity measure salinity?
Water is a poor conductor, high salts would have high conductivity
28
What is Cation Exchange Capacity? How does it relate to texture?
The sum of exchangeable cations that a soil can absorb. High in clay and low in sand
29
What does a high CEC value mean for the soil?
More clay and OM, greater water holding capacity, more fertile soil, better nutrient retention
30
What does a low CEC value mean for the soil
Fewer positions to hold cations Low clay content
31
Define limiting factor
The growth factor that limits the amount of growth. The lowest plank in a barrel that prevents yield from exceeding a certain point
32
What are pros/cons of increasing limiting factor
Pro: increased availability leads to increased growth Con: something else wioll become limited
33
What process outputs Nitrogen for plants?
Mineralization turns organic N to inorganic N
34
Is volatilization an input or output?
Volzatilization outputs N into atmosphere
35
Define immobilization
Immobilizing nutrients - Converting inorganic N into organic forms
36
Define fixation
Ammonium ions attracted to negatively charged surfaces of clay
37
Define nitrification
N going up - Conversion of ammonium (NH4+) into nitrate(NO3-) by autotrophs It’s like stacking legos—adding oxygen (oxidation) to make nitrogen more available.
38
What are the two bacteria in nitrification?
Nitrosomonous and nictrobacter
39
What does nitrosomonous do?
SOMMONIUM - Ammonium into nitrite
40
What does nitrobacter do?
NictrobActer(nitrAte) Nitrite into nitrate
41
What is gained and lossed in nitrification?
Gain nitrate and lose ammonium
42
What is leeching
Loss of water soluble plant nutrients into ground water
43
What is denitrification
N going down - nitrate NO3- is broken down to N2 gas
44
What is gained and losed in denitrification
Adds ammonium Loses nitrate
45
Where is nitrogen mainly stored q
Atmosphere
46
Where is sulfur mainly stored
Organic matter
47
What is sulfate and where is it found
Inorganic sulfur that is easily stabilized, found in arid regions
48
What is sulfide and where is it found?
Inorganic sulfure that must be oxidized before uptaken, found in humid regions
49
What is atmospheric sulfur
Gasses that get oxidized into sulfates and sulfuric acid (acid rain)
50
3 storages of sulfur
Organic matter, minerals, and atmospheric
51
How does sulfur move by oxidation and reduction
Oxidation: makes sulfuric acid by autotrophic bacteria Reduction: sulfate > sulfide
52
Is phosphorous more common in soil or atmosphere?
Soils
53
What are the 3 pairs of phosphorous movement
Immobilization/mineralization Precipitation/weathering Adsorption/desorption
54
How is potassium held
In minerals (not available) In fixed forms (moderately available) Exchangable forms (readily available)
55
Where is Ca/Mg found?
Minerals (not available) Trapped in humus (slowly available) Exchangable forms (readily available)
56
Describe the Ca/Mg ratio
Ca:Mg in plants is more important than Ca:Mg in soil. Mg is easily leeched by available at less exchange sites Generally more Ca than Mg
57
Functions of roots (primary)
Hold plant in place Absorb water/nutrients
58
Secondary functions of roots
Storage Synthesize organic compounds Transport Secretion Generate new shoots
59
4 factors in compaction issue for roots
Crushed macropores > low bulk density Decreased pore space > low field capacity Less air Finer micropores > increased wilting point
60
Largest issue for root growth
Compaction
61
What do mycorrhizae provide for roots
Increase water availability Protect from fungal/bacterial pathogens
62
Are mycorrhizae found in nutrient rich or poor soils
Poor
63
Two kidns of mycorrhizae
Ectomycorrhizae: non-penetrating Endomycorrhizae: penetrating
64
What 2 things do soil organisms provide for an ecosystem
Increase species diversity Increase functional diversity
65
Describe functional redundancy and what it leads to
Functional redundancy: same jobs being completed by different species Stability Resilience
66
Describe primary consumers and primary producers
Primary Consumers: heterotrophs > herbivores/detritivores Primary Producers: autotrophs > photoautotrophs/chemoautotrophs
67
What are heterotrophs in a food web?
Heterotrophs include primary consumers such as herbivores and detritivores.
68
What are autotrophs in a food web?
Autotrophs are primary producers like photoautotrophs and chemoautotrophs.
69
Who are considered secondary consumers?
Secondary consumers are predators including herbivores
70
How do secondary consumers influence microbial activity?
They directly influence microbial activity.
71
What are tertiary consumers?
Tertiary consumers are predators of primary and secondary consumers
72
How do tertiary consumers contribute to nutrient cycling?
Their predation releases nutrients into the soil that were bound in the cells of living secondary consumers.
73
What do microbial decomposers consume?
They directly consume plants and decompose finely shredded material and dead animal bodies.
74
Where else are microbial decomposers active?
They are active in the digestive systems of other organisms.
75
What are saprophytic microorganisms?
They are decomposers like fungi and bacteria that feed on dead tissue.
76
What do saprophytic microorganisms do?
They break down compounds
77
What is decomposition?
The breakdown of large organic molecules into smaller
78
What results from the decay of plant proteins?
Carbon dioxide (CO2)
79
What happens to amino acids during decomposition?
Amino acids are broken down into inorganic ions.
80
What occurs when organic tissue is added to aerobic soil?
Enzymatic oxidation of carbon compounds and release or immobilization of essential nutrients.
81
What are the products of enzymatic oxidation in soil?
CO2
82
How are essential nutrient elements affected during decomposition?
They are either released or immobilized through specific chemical reactions.
83
What are the main drivers of decomposition?
Temperature
84
What are examples of high-quality organic matter?
Sugars
85
What are other components of organic matter quality?
Crush proteins
86
Define mineralization
Making minerals from decomposed OM
87
What is DNRA
Dissimilatory Nitrate Reduction to Ammonium: Microbial process that reverses nitrification - NO3- > NH4+
88
How does water move in saturated soils?
Freely via gravity. Preferential flow occurs through macropores
89
How does water move through unsaturated soils?
Water moves slowly by capillary action, driven by matric potential. Wet > dry
90
How does clay texture affect soil water movement
Clay holds more water because of small pores that hold water tightly

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