1
Q
Define Rhizosphere
A
- anything impacted by plant
2
Q
Define Rhizoplane
A
- on surface of plant root
3
Q
What are the 2 broad groups of soils?
A
- mineral soils
- organic soils
4
Q
What is the rhizosphere effect
A
- importance of rhizosphere to promote microbial activity
- prefer to be attached to soil particles
5
Q
Why is nitrate mobile in clay based soils?
A
- has same charge as clay (naturally repelling)
- ammonia has positive charge
6
Q
Where does most extensive microbial growth take place?
A
soil particles within rhizosphere
7
Q
What factors affect microbial activity in soil?
A
- availability of water
- O2 availability
- nutrient status
8
Q
What is optimal Aw measure?
A
- close to 1 (0.96 is microbial optimum)
9
Q
Explain the O horizon conditions
A
- undecomposed plant materials
- dry
- susceptible to leaching
10
Q
What is the water activity on O horizon
A
salts and sugars not favourable
11
Q
Explain the A horizon conditions
A
- MOST FAVOURABLE
- lots of organic material (nutrition) and dead plant material
- roots present to pull in recycled nutrition and oxygen
- O2 drives heterotrophic and organotrophic activity
- protected from external environment and UV radiation
12
Q
Explain the B horizon conditions
A
- some activity and accumulation of humic material
- some microbial activity (lithotrophs)
13
Q
Explain the C horizon conditions
A
bottom up
hardly any microbial activity
14
Q
What are the different soil horizons and what one is the best?
A
- O, A, B, C
- A is best
15
Q
Why is A horizon the best?
A
- has oxygen and nutrients (roots)
- has organic dead plant material
- away from sun radiation
16
Q
What are characteristics of deep soil?
A
- mainly anaerobic unless oxygen is available
- facultative anaerobes/sulfate reducers/methanogens
-prokaryotes - low groundwater flow
- low metabolic activity
17
Q
How does deep soil occur?
A
- bedrock/tectonic plate shift
- fissions release O2
18
Q
What does in situ mean
A
on place, at that site
Bi374
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