(6.3) Nitrogen Cycle

Question 1

4 stages

Answer 1

Ammonification
Nitrification
Nitrogen fixation
Denitrification

Question 2

Ammonification

Answer 2

Production of ammonia from org ammonium containing compounds
-Urea/Proteins/Nucleic Acid & Vitamins
SO feed on these: release ammonia, forming ammonium ions in soil
(N returns to NL component of ecosystem)

Question 3

Nitrification

Answer 3

Oxidation reaction of ammonium ions to nitrate ions
Carried out by nitrifying bacteria

Oxidation of ammonium ions to NO-2
= of NO-2 -> NO-3

Question 4

Nitrifying bacteria

Answer 4

Nitrogen Fixation

Req 02
Soil w/ air spaces
Ploughing
Good drainage prevents water being stuck!

Question 5

Nitrogen fixation

Answer 5

N gas -> N containing compounds carried out industrially &;
Free living NFixing bacteria; reduce gaseous N to ammonia to make AA
When they die; release N rich compounds

Mutualistic Nfixing bacteria; live in nodules of roots of plants (peas & beans) - MNFB receives carbs from plant. Plant receives AA

Question 6

Denitrification - removes N!

Answer 6

Soil = H20 logged // less 02 (less NFB) & +

Anaerobic denitrifying bacteria

Soil nitrates -> gaseous nitrogen
Means less N for plants

Solution; aerate soil for less DNB & + productivity

Question 7

What is nitrogen?

Answer 7

Org req N to form proteins, nucleic acid & other N containing compounds

78% ats = N
only few orgs can take N directly
Plants take N ions from soil (here N enters living comp of ecosystem)
Animals = Eat N containing compounds & digesting plants
Nat ecosystem = nitrate recycled
Agricultural ecosystem = fertilisers
Decomposition ; returns N to soil - v lil N other resources