(This was the less popular question in this section and many candidates avoided it. those candidates
who attempted it scored low marks. Many candidates had an idea of the terms, but mixed the
explanations interchanging the explanation for nitrification with denitrification and vice versa and
most candidates could not explain how nitrogen from urine gets to the roots of plants showing the
inability of many candidates to apply theoretical knowledge to practical situations. Expected
answers include:
Putrefaction: A process by which agents of decay/saprophytic/putrifying bacteria/fungi,
decomposedlbreakdown; dead organic remains/waste products of other organisms; into ammonium
compounds/nitrates.
nitrogen fixation: the process by which free atmospheric nitrogen; is converted to nitrate in the soil;
by thunder stormlbacteria in root noodles oflegumes/soil.
nitrification: the conversion of anunonia/ammonium compounds; to nitrites; then to nitrates; by
nitrifying bacteria.
Denitrification: This is the conversion of nitrates; III the soil to atmospheric nitrogen; by
denitrifying bacteria/fungi.
Differences between Nitrogen fixation and Denitrification
Nitrogen Fixation |
Denitrification |
Free atmospheric nitrogen is added to the |
Nitrates in the soil is converted into |
soil; |
atmospheric nitrogen; |
Nitrogen fixing bacteria are involved; |
Denitrifying bacteria are involved; |
It involves symbiotic and non-symbiotic |
Purely non-symbiotic organismslbacteria; |
organisms/bacteria; |
|
Moderate soil temperature is required. |
High temperature is required |
How Nitrogen from urine gets to the roots of plants
When a person passes urine in the soil;
Ammonium compound/urea present in urine; is converted into nitrite;
by nitrifying bacteria/nitrosamines;
The nitrites are oxidized to nitrates;
by other nitrifying bacteria/nitro bacteria;
Roots of plants absorb the nitrates. |
