Soils exam 1 Flashcards
Is reduction good for plants?
No
Oxidation if pyrite produces extreme acidity and soluble iron and sulfur
Acid mine drainage
What happens if Eh falls below .32 volts
A soil is devoid of o2 and other elements are used for microbial metabolism
The ability if soils to bind chemical substances depends on these 3 things:
Chemical characteristics if substance
Characteristics if soil
Oxygen concentration does what as soil depth increases?
Decreases
Preferential or bypass flow
Transports chemicals to groundwater more rapidly via macro pores
What is mass flow?
Physical movement if air due to fluctuations in moisture content
What is biological 0?
5 degrees centigrade
What 3 factors affect soil aeration and Eh?
Drainage and nacroporosity
Respiration rates
Soil heterogeneity
What happens to microbial activity as temperature rises?
It doubles for every 10 degrees and dies around 50 or 60
What can anaerobic conditions in soil lead to?
Production of reduced nitrogen gases, methane gases, hydrogen sulfide, ethylene
What does water do to diffusion?
Slows it because it moves 10000 times slower
What is aspect?
The direction of slope of a surface
Loss of electrons in a substance
Oxidation
What is albedo?
The fraction of sunlight reflected?
Anaerobic decomposition can lead to…
Toxins
What is the electron receptor for respiration?
Oxygen
What is a veal action process?
Seeds needing cold treatment to germinate
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
What is the more important form of soil gas exchange?
Diffusion
When does run off occur
When accumulation exceeds rare if infiltration or soil storage capacity
What is the partial pressure gradient?
A difference in every potential of gas concentration
Provides maximum opportunity for soils to bind chemicals:
Matrix flow
Why does diffusion occur?
Concentration gradients
What 2 things regulate o2 availability?
Soil macro porosity and water content
Greatly decreases the ability if a soil to bond chemicals
Macropore flow
High saturation levels does what to o2 content?
Lowers it
What kinds if soils are under frequent reducing conditions?
Wetland soils —> histosols
What two ways does soul gas exchange?
Mass flow and diffusion
What are concentrations of co2 like beneath the soil surface.
It can be 10 to 100 times greater and be toxic
At what percentage air porosity dies microbial and root respiration cease?
10
Eutrophication
Excess nutrients (phosphorus) that leads to excessive aquatic growth and ultimately oxygen depletion
Material that reduces evaporation and controls weeds
Mulch
Interception
Precipitation that never reaches soil due to vegetation
The gain of electrons
Reduction
1:1 type composed of which sheets
1 tetrahedra, 1 octahedral
Tetrahedral sheet is composed of:
4 oxygen
1 silicon at center
1:1 clay type example
Kaolinite
2:1 clay groups without shrinking and swelling:
Fine grained micas(ilites) and chlorites
Examples of 2:1 clays
Smectites
Octahedral sheet is made of which atoms
6 oxygen/hydroxyl
With an aluminum/magnesium at center
Eutrophication
Excess nutrients (phosphorus) in fresh water leading to excessive aquatic growth and ultimately oxygen depletion
2:1 type made if which sheets
2 tetrahedra, 1 octahedral
2:1 type shrinking and swelling clay groups
Smectites
Vermiculites
Important silicate clays
Phyllo silicates
Difference between anions and cations
Anions are negative cations are positive
What happens when a soil accepts H
It lowers the soils ph
What is CEC?
The amount of cations a soil can contain
If you increase CEC, what happens to plants ability to store nutrients?
Increases
What 3 factors raise CEC?
Amount of clay
Amount if organic matter
Increase in soil ph
How do soils acidify?
Respiration in roots and microbes creating co2 that reacts with water to create weak acids
What is a very toxic element to plants?
Al3+
What are the 3 pools of soil acidity?
Active acidity
Exchangeable acidity
Residual acidity
What determines active acidity?
Ph
What determines exchangeable acidity?
Cation exchange?
What determines residual acidity?
Ph buffered extractent
When do herbicides become soluble?
At high ph
When do metals become soluble?
At low ph
When little or no mg is in a carbonate it is
Calcitic
When a carbonate has increasing amounts if mg it becomes
Dolomitic
On what 4 things does a lining requirement depend?
Change in ph required
Buffering capacity
Type of lime used
The fineness of lime
What is cce?
The neutralizing value of lining material
How is salinity measured?
Electrical conductivity
How is sod ivory measured?
Exchangeable sodium percentage
