Soil biology, Lecture 30 Flashcards
1
Q
SOM
A
Soil organic matter
2
Q
SOC
A
Soil organic carbon
3
Q
Determining SOM
A
loss on ignition,
360 degrees C, for 2 to 16 hours
4
Q
Determination of SOC
A
combustion and measurement of CO2:
- add Sn or CuO catalyst and burn at high temp.
- generally gas chromatography is used to measure CO2
5
Q
How is plant material transformed from one organic compound to another?
A
by organisms in the soil
6
Q
Organisms create
3
A
by-products, wastes and cell tissue
7
Q
Humus
newly-formed humus:
A
- a combination of resistant materials from the original plant tissue
- compounds synthesized as part of the microorganisms’ tissue, which remain as the organisms die
8
Q
Functions of humus
A
- holds water and nutrients
- maintains a strong crumb structure by sticking together and therefore reduces soil erosion
- provides some nutrients (N&P) as it is decayed slowly by microbial activity
- creates good soil ‘tilth’
- coats the sand, silt and clay particles, making them darker, the darker the colour, the greater the amount of soil humus present
9
Q
Rate of humus decomposition
A
2.5%
10
Q
Soil biomass
A
The total mass of living matter within the soil
11
Q
Agricultural soils contain much fewer organisms, percentage?
A
20-50%
12
Q
Groups of organisms found in soil?
4
A
microbes, microfauna, mesofauna, macrofauna
13
Q
Microbes found in soil
4
A
- bacteria
- actinomycetes
- fungi
- algae
14
Q
Microfauna found in soil
2
A
- protozoa
2. nematodes
15
Q
Mesofauna found in soil
3
A
- collembola
- mites
- enchytraeids
