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Flashcards in Soils exam 1 Deck (64)
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0
Q

Is reduction good for plants?

A

No

1
Q

Oxidation if pyrite produces extreme acidity and soluble iron and sulfur

A

Acid mine drainage

2
Q

What happens if Eh falls below .32 volts

A

A soil is devoid of o2 and other elements are used for microbial metabolism

3
Q

The ability if soils to bind chemical substances depends on these 3 things:

A

Chemical characteristics if substance

Characteristics if soil

4
Q

Oxygen concentration does what as soil depth increases?

A

Decreases

5
Q

Preferential or bypass flow

A

Transports chemicals to groundwater more rapidly via macro pores

6
Q

What is mass flow?

A

Physical movement if air due to fluctuations in moisture content

7
Q

What is biological 0?

A

5 degrees centigrade

8
Q

What 3 factors affect soil aeration and Eh?

A

Drainage and nacroporosity

Respiration rates

Soil heterogeneity

9
Q

What happens to microbial activity as temperature rises?

A

It doubles for every 10 degrees and dies around 50 or 60

10
Q

What can anaerobic conditions in soil lead to?

A

Production of reduced nitrogen gases, methane gases, hydrogen sulfide, ethylene

11
Q

What does water do to diffusion?

A

Slows it because it moves 10000 times slower

12
Q

What is aspect?

A

The direction of slope of a surface

13
Q

Loss of electrons in a substance

A

Oxidation

14
Q

What is albedo?

A

The fraction of sunlight reflected?

15
Q

Anaerobic decomposition can lead to…

A

Toxins

16
Q

What is the electron receptor for respiration?

A

Oxygen

17
Q

What is a veal action process?

A

Seeds needing cold treatment to germinate

18
Q

The measure in volts of how aerobic or anaerobic a system is. A measure of electrical potential of a substance to give up electrons

A

Redox potential

19
Q

What is the more important form of soil gas exchange?

A

Diffusion

20
Q

When does run off occur

A

When accumulation exceeds rare if infiltration or soil storage capacity

21
Q

What is the partial pressure gradient?

A

A difference in every potential of gas concentration

22
Q

Provides maximum opportunity for soils to bind chemicals:

A

Matrix flow

23
Q

Why does diffusion occur?

A

Concentration gradients

24
Q

What 2 things regulate o2 availability?

A

Soil macro porosity and water content

25
Q

Greatly decreases the ability if a soil to bond chemicals

A

Macropore flow

26
Q

High saturation levels does what to o2 content?

A

Lowers it

27
Q

What kinds if soils are under frequent reducing conditions?

A

Wetland soils —> histosols

28
Q

What two ways does soul gas exchange?

A

Mass flow and diffusion

29
Q

What are concentrations of co2 like beneath the soil surface.

A

It can be 10 to 100 times greater and be toxic

30
Q

At what percentage air porosity dies microbial and root respiration cease?

A

10

31
Q

Eutrophication

A

Excess nutrients (phosphorus) that leads to excessive aquatic growth and ultimately oxygen depletion

32
Q

Material that reduces evaporation and controls weeds

A

Mulch

33
Q

Interception

A

Precipitation that never reaches soil due to vegetation

34
Q

The gain of electrons

A

Reduction

35
Q

1:1 type composed of which sheets

A

1 tetrahedra, 1 octahedral

36
Q

Tetrahedral sheet is composed of:

A

4 oxygen

1 silicon at center

37
Q

1:1 clay type example

A

Kaolinite

38
Q

2:1 clay groups without shrinking and swelling:

A

Fine grained micas(ilites) and chlorites

39
Q

Examples of 2:1 clays

A

Smectites

40
Q

Octahedral sheet is made of which atoms

A

6 oxygen/hydroxyl

With an aluminum/magnesium at center

41
Q

Eutrophication

A

Excess nutrients (phosphorus) in fresh water leading to excessive aquatic growth and ultimately oxygen depletion

42
Q

2:1 type made if which sheets

A

2 tetrahedra, 1 octahedral

43
Q

2:1 type shrinking and swelling clay groups

A

Smectites

Vermiculites

44
Q

Important silicate clays

A

Phyllo silicates

45
Q

Difference between anions and cations

A

Anions are negative cations are positive

46
Q

What happens when a soil accepts H

A

It lowers the soils ph

47
Q

What is CEC?

A

The amount of cations a soil can contain

48
Q

If you increase CEC, what happens to plants ability to store nutrients?

A

Increases

49
Q

What 3 factors raise CEC?

A

Amount of clay
Amount if organic matter
Increase in soil ph

50
Q

How do soils acidify?

A

Respiration in roots and microbes creating co2 that reacts with water to create weak acids

51
Q

What is a very toxic element to plants?

A

Al3+

52
Q

What are the 3 pools of soil acidity?

A

Active acidity
Exchangeable acidity
Residual acidity

53
Q

What determines active acidity?

A

Ph

54
Q

What determines exchangeable acidity?

A

Cation exchange?

55
Q

What determines residual acidity?

A

Ph buffered extractent

56
Q

When do herbicides become soluble?

A

At high ph

57
Q

When do metals become soluble?

A

At low ph

58
Q

When little or no mg is in a carbonate it is

A

Calcitic

59
Q

When a carbonate has increasing amounts if mg it becomes

A

Dolomitic

60
Q

On what 4 things does a lining requirement depend?

A

Change in ph required
Buffering capacity
Type of lime used
The fineness of lime

61
Q

What is cce?

A

The neutralizing value of lining material

62
Q

How is salinity measured?

A

Electrical conductivity

63
Q

How is sod ivory measured?

A

Exchangeable sodium percentage