Soil biology, Lecture 30

Question 1

SOM

Answer 1

Soil organic matter

Question 2

SOC

Answer 2

Soil organic carbon

Question 3

Determining SOM

Answer 3

loss on ignition,

360 degrees C, for 2 to 16 hours

Question 4

Determination of SOC

Answer 4

combustion and measurement of CO2:

• add Sn or CuO catalyst and burn at high temp.
• generally gas chromatography is used to measure CO2

Question 5

How is plant material transformed from one organic compound to another?

Answer 5

by organisms in the soil

Question 6

Organisms create

3

Answer 6

by-products, wastes and cell tissue

Question 7

Humus

newly-formed humus:

Answer 7

1. a combination of resistant materials from the original plant tissue
2. compounds synthesized as part of the microorganisms’ tissue, which remain as the organisms die

Question 8

Functions of humus

Answer 8

1. holds water and nutrients
2. maintains a strong crumb structure by sticking together and therefore reduces soil erosion
3. provides some nutrients (N&P) as it is decayed slowly by microbial activity
4. creates good soil ‘tilth’
5. coats the sand, silt and clay particles, making them darker, the darker the colour, the greater the amount of soil humus present

Question 9

Rate of humus decomposition

Answer 9

2.5%

Question 10

Soil biomass

Answer 10

The total mass of living matter within the soil

Question 11

Agricultural soils contain much fewer organisms, percentage?

Answer 11

20-50%

Question 12

Groups of organisms found in soil?

4

Answer 12

microbes, microfauna, mesofauna, macrofauna

Question 13

Microbes found in soil

4

Answer 13

1. bacteria
2. actinomycetes
3. fungi
4. algae

Question 14

Microfauna found in soil

2

Answer 14

1. protozoa

2. nematodes

Question 15

Mesofauna found in soil

3

Answer 15

1. collembola
2. mites
3. enchytraeids

Question 16

Macrofauna found in the soil

3

Answer 16

1. arthropods
2. vertebrates
3. earthworms

Question 17

The distribution of organisms soils is influenced by and influences…

Answer 17

pore distribution

Question 18

Rhizosphere

Answer 18

The narrow region of soil which is influenced by the root microbiome (googled)

Question 19

Root microbiome

Answer 19

Microbes in and around (associated with) plant roots

Question 20

Soil quality

Answer 20

The capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality and support human health and habitation. (Toth et al, 2007)

Question 21

Soil health

Answer 21

Change in soil quality over time due to human use and management or to natural events.

Question 22

Soil quality should be protected…

Answer 22

as seriously as air and water quality