Microbiology of soil

Question 1

Soil?

Answer 1

The loose outer material of Earth’s surface, distinct from bedrock (solid rock).

Question 2

Soil can be divided into two broad groups

Answer 2

• Mineral soils

- Organic soil

Question 3

What’s mineral soil ?

Answer 3

derived from rock weathering ( breaking down of rocks) and other inorganic material s

Question 4

where do u find more mineral soil?

Answer 4

in terrestrial environment

Question 5

Organic soils?

Answer 5

derived from the sedimentation in bogs and marshes

Question 6

Soils are composed of ?

Answer 6

–Inorganic mineral matter (~40% of soil volume)
–Organic matter (~5%)
–Air and water (~50%)
–Living organisms

Question 7

soil is divided into 4 layers?

Answer 7

• O horizon
• A horizon
• B horizon
• C horizon

Question 8

O horizon?

Answer 8

layer of undecomposed plant materials

Question 9

A horizon ?

Answer 9

Surface soil

Question 10

What’s is done at the suface soil level ?

Answer 10

• high in organic matter
• Dark in color
• tilled for agriculture
• microbial activity high

Question 11

B horizon?

Answer 11

Subsoil

Question 12

in b horizon what happens?

Answer 12

• Minerals,humus
• little organic matter
• microbial activity detectable but lower than at the A horizon

Question 13

C horizon?

Answer 13

soil base(develops directly from underlying bedrock,microbial activity generally very low )

Question 14

HUMUS?

Answer 14

Dead plant material that is resistant to decomposition

Question 15

humus keeps?

Answer 15

water and nutrients in the soil

Question 16

humus is therefore good for ?

Answer 16

soil fertility,increase amount of water and nutriments further down in the soil

Question 17

What’s the more dominant bacteria in soil environment ?

Answer 17

proteobacteria

Question 18

Most microbial growth takes place on ?

Answer 18

the surfaces of soil particles

Question 19

The availability of water the most important?

Answer 19

factor influencing microbial activity in surface soils

Question 20

in sand u find and how well does it retains water ?

Answer 20

-0.1-2 mm particles

water drains quicky

Question 21

in silt u find and how well does it retains water ?

Answer 21

-0.002-0.1 mm particles

retains water to the right extent

Question 22

in clay what do u find?

Answer 22

les than 0.002 particles

water retained too well soil becomes anoxic

Question 23

what is the most important factor in subsurface environments?

Answer 23

Nutrient availability

Question 24

What do u find on top few centimeters of soil?

Answer 24

• Bacteria
• fungi
• Protozoa
• Algae

Question 25

Prokaryotes are largely responsible for ?

Answer 25

• production of the humus
• release of minerals from soil particles(production of acids from organic coumpounds solubilize the minerals )
• cycling of nutrients
• nitrogen fixation

Question 26

What’s rhizosphere?

Answer 26

soil that surrounds plant

roots and receive plant secretions.

Question 27

What’s mycorrhizae ?

Answer 27

association of fungi with

plant roots.

Question 28

(CC) CO2 in the atmosphere is the most rapidly transferred?

Answer 28

carbon reservoir

Question 29

(CC) Co2 is fixed by ?

Answer 29

photosynthetic land plants and marine microbes

Question 30

(CC) returned to the atmosphere by ?

Answer 30

• respiration

- anthropogenic activites (use of fossil fuel)

Question 31

(CC)What is one of the largest source of CO2 released to the atmosphere?

Answer 31

microbial decomposition

Question 32

(CC)Other major source ?

Answer 32

CH4 the other major end product of decomposition