Midterm 3

Question 1

Ammonia

Answer 1

NH3
Gas or soluble
Oxidation number -3

Question 2

Ammonium

Answer 2

NH4+
Soluble
Oxidation number -3

Question 3

Nitrate

Answer 3

NO3-
Soluble
Oxidation number +V

Question 4

Nitrite

Answer 4

NO2-
Soluble
+3

Question 5

Nitrogen

Answer 5

N2
Gas or soluble
0

Question 6

Describe organic forms of nitrogen

Answer 6

1. Nitrogen contained in SOM occurs as a wide range of compounds
2. Amino acid-N is most abundant

Question 7

How much N is contained in microbial biomass and list the C/N ratio for fungal and bacterial cells.

Answer 7

5-10% of total soil N is contained in microbial biomass. Fungal cells have a C/N ratio of 10:1 and bacterial cells have a C/N ratio of 4:1.

Question 8

Immobilization

Answer 8

NH4/ammonium and NO3-/nitrate into organic N (amino acids).

Question 9

Ammonification

Answer 9

Conversion of organic N compounds into ammonium (NH4+).

Question 10

Nitrification

Answer 10

Ammonium (NH4+) oxidation to nitrite and nitrate (NO2- and NO3-).

Question 11

Denitrification

Answer 11

Reduction of nitrate (NO3-) to nitrogen gas (N2). Several intermediates are involved.

Question 12

Gross mineralization

Answer 12

The total amount of organic nitrogen converted into inorganic forms (primarily ammonium) through microbial activity in the soil over a given period.
(Overall potential)

Question 13

Net mineralization

Answer 13

The amount of inorganic nitrogen (e.g., ammonium) remaining in the soil after accounting for microbial uptake and other processes like immobilization.
(What’s available)