chapter 14

Question 1

what is nitrogen fixation?

Answer 1

it is the biochemical process by which atmospheric nitrogen (N2) is changed into forms used by plants

Question 2

what bacteria affects nitrogen fixation

Answer 2

rhizobium, actinomycetes, and blue green algae

Question 3

advantage of nitrogen fixation

Answer 3

eliminates need for nitrogen fertilizer for the legume crop, provides residual nitrogen for subsequent crop

Question 4

what are the 4 systems of nitrogen fixation

Answer 4

1. symbiotic and nodule forming system with legumes
2. symbiotic and nodule forming systems with non legumes
3. symbiotic and nodule forming system
4. non symbiotic system

Question 5

summary of symbiotic and nodule forming system with legumes

Answer 5

plant involved: legumes
Soil organism involved: bacteria (rhizobium)
where is nitrogen fixed: root nodules
how much N is fixed? 25-220 lbs/acre per year

Question 6

which legumes are best

Answer 6

alfalfa: 130-220 lb N/per acre per year
Clover: 85-130
Soybean: 44-130
other: 25-88

Question 7

summary of symbiotic and nodule forming systems with non legumes

Answer 7

plant involved: non legumes

Soil organism involved: Actinomycetes

Question 8

summary of symbiotic and nodule forming system

Answer 8

plants involved: various plants and microorganisms
soil organism involved: blue-green algae, bacteria
where is the N fixed: around roots and on leafs
how much N is fixed: 4-25 lb /per acre per year

Question 9

summary of non symbiotic system

Answer 9

plant involved: none
soil organism involved: blue-green algae, bacteria
where is N fixed: soil or water independent from plants
how much N is foxed per year: 4-44 lb/per acre per year

Question 10

what are the 2 general types of soil bacteria

Answer 10

autotrophs

heterotrophs

Question 11

what do autotrophs play an important role in

Answer 11

1. nitrification processes
2. denitrification processes
3. nitrogen fixation

Question 12

what do heterotrophs play an important role in

Answer 12

1. denitrification in soils
2. nitrogen fixation
3. mineralization of OM to yield ammonium
4. immobilization of nitrogen

Question 13

what are autotrophs

Answer 13

• are essential to all life because they are the mane producers at the base of all food chains
• two types of autotrophs, both require CO2 to grow

Question 14

where do autotrophs get there food from

Answer 14

• sunlight (photoautotrophs)

- oxidation of substances such as: nitrogen, iron, or sulphur (chemoautotrophs)

Question 15

what are heterotrophs

Answer 15

organisms that make use of food that comes from other organisms in the from of: fats, carbohydrates and proteins
- use OM to obtain carbon for growth