Soils Exam 2 Flashcards Preview

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Flashcards in Soils Exam 2 Deck (35)
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0
Q

When does run off occur

A

When accumulation exceeds rare if infiltration or soil storage capacity

1
Q

Interception

A

Precipitation that never reaches soil due to vegetation

2
Q

Material that reduces evaporation and controls weeds

A

Mulch

3
Q

Eutrophication

A

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

4
Q

Oxidation if pyrite produces extreme acidity and soluble iron and sulfur

A

Acid mine drainage

5
Q

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

A

Chemical characteristics if substance

Characteristics if soil

6
Q

Provides maximum opportunity for soils to bind chemicals:

A

Matrix flow

7
Q

Greatly decreases the ability if a soil to bond chemicals

A

Macropore flow

8
Q

Preferential or bypass flow

A

Transports chemicals to groundwater more rapidly via macro pores

9
Q

Oxygen concentration does what as soil depth increases?

A

Decreases

10
Q

High saturation levels does what to o2 content?

A

Lowers it

11
Q

What are concentrations of co2 like beneath the soil surface.

A

It can be 10 to 100 times greater and be toxic

12
Q

What can anaerobic conditions in soil lead to?

A

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

13
Q

What 2 things regulate o2 availability?

A

Soil macro porosity and water content

14
Q

What two ways does soul gas exchange?

A

Mass flow and diffusion

15
Q

What is the more important form of soil gas exchange?

A

Diffusion

16
Q

What is mass flow?

A

Physical movement if air due to fluctuations in moisture content

17
Q

Why does diffusion occur?

A

Concentration gradients

18
Q

What is the partial pressure gradient?

A

A difference in every potential of gas concentration

19
Q

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

A

10

20
Q

What does water do to diffusion?

A

Slows it because it moves 10000 times slower

21
Q

Loss of electrons in a substance

A

Oxidation

22
Q

The gain of electrons

A

Reduction

23
Q

What is the electron receptor for respiration?

A

Oxygen

24
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

25
Q

What happens if Eh falls below .32 volts

A

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

26
Q

Anaerobic decomposition can lead to…

A

Toxins

27
Q

What 3 factors affect soil aeration and Eh?

A

Drainage and nacroporosity

Respiration rates

Soil heterogeneity

28
Q

Is reduction good for plants?

A

No

29
Q

What kinds if soils are under frequent reducing conditions?

A

Wetland soils —> histosols

30
Q

What is a veal action process?

A

Seeds needing cold treatment to germinate

31
Q

What is biological 0?

A

5 degrees centigrade

32
Q

What happens to microbial activity as temperature rises?

A

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

33
Q

What is albedo?

A

The fraction of sunlight reflected?

34
Q

What is aspect?

A

The direction of slope of a surface