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Flashcards in Soils Exam 2 Deck (35):
0

Interception

Precipitation that never reaches soil due to vegetation

1

When does run off occur

When accumulation exceeds rare if infiltration or soil storage capacity

2

Material that reduces evaporation and controls weeds

Mulch

3

Eutrophication

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

4

Oxidation if pyrite produces extreme acidity and soluble iron and sulfur

Acid mine drainage

5

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

Chemical characteristics if substance
Characteristics if soil

6

Provides maximum opportunity for soils to bind chemicals:

Matrix flow

7

Greatly decreases the ability if a soil to bond chemicals

Macropore flow

8

Preferential or bypass flow

Transports chemicals to groundwater more rapidly via macro pores

9

Oxygen concentration does what as soil depth increases?

Decreases

10

High saturation levels does what to o2 content?

Lowers it

11

What are concentrations of co2 like beneath the soil surface.

It can be 10 to 100 times greater and be toxic

12

What can anaerobic conditions in soil lead to?

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

13

What 2 things regulate o2 availability?

Soil macro porosity and water content

14

What two ways does soul gas exchange?

Mass flow and diffusion

15

What is the more important form of soil gas exchange?

Diffusion

16

What is mass flow?

Physical movement if air due to fluctuations in moisture content

17

Why does diffusion occur?

Concentration gradients

18

What is the partial pressure gradient?

A difference in every potential of gas concentration

19

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

10

20

What does water do to diffusion?

Slows it because it moves 10000 times slower

21

Loss of electrons in a substance

Oxidation

22

The gain of electrons

Reduction

23

What is the electron receptor for respiration?

Oxygen

24

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

Redox potential

25

What happens if Eh falls below .32 volts

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

26

Anaerobic decomposition can lead to...

Toxins

27

What 3 factors affect soil aeration and Eh?

Drainage and nacroporosity

Respiration rates

Soil heterogeneity

28

Is reduction good for plants?

No

29

What kinds if soils are under frequent reducing conditions?

Wetland soils ---> histosols

30

What is a veal action process?

Seeds needing cold treatment to germinate

31

What is biological 0?

5 degrees centigrade

32

What happens to microbial activity as temperature rises?

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

33

What is albedo?

The fraction of sunlight reflected?

34

What is aspect?

The direction of slope of a surface