Nitrogen Cycle

Question 1

Nitrogen-fixing

Answer 1

Conversion of N2 gas into ammonium compounds by nitrogen-fixing bacteria Rhizobium found inside root nodules of leguminous plants in a symbiotic relationships.

Question 2

Ammonification

Answer 2

Conversion of nitrogen containing compounds into amino acids and then into ammonium compounds. This is carried out by decomposers, which secrete digestive enzymes into dead materials to break them down into small soluble molecules to release trapped energy.

Question 3

Nitrification

Answer 3

Conversion of ammonium compounds into nitrites (nitrosomonas) and then nitrates (nitrobacter) by nitrifiying bacteria. It requires O2 so only occurs in aerated soils. Plants are then able to take nitrates up via active transport. (NH4+ > NO2- > NO3-).

Question 4

Denitrification

Answer 4

Conversion of nitrates in soil into N2 gas by denitrifying bacteria. Occurs in anaerobic soils e.g waterlogged/compacted conditions. This makes the soil less fertile as less nitrates are available for growth for plant.