SS2 Lesson Note on the Nitrogen; Carbon; Water and Phosphorous Cycles

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Processes of Nitrogen Transformation include:

1. Oxidation during lightening: Nitrogen in the air combines with oxygen to form oxides of nitrogen such as nitric-oxides. Nitrogen peroxide and nitric-oxide. These undergo further oxidation to from nitrogen-dixoide. When this dissolves in water during rain. It forms nitrous acid and nitric acid. These are converted to nitrates and filter into the soil with rain water.
2. By ammonification and nitrification: Ammonification is the process whereby ammonium compounds are formed from decomposing organic materials as well as from the waste products from plant and animals such as urine and faeces through the action of purifying bacteria. The ammonia so released is converted to nitrites by a group of initiating bacteria called Nitrosomonas. The nitrites are converted to nitrates by another bacterium called Nitrobacter. The nitrates formed are absorbed from the soil while some are lost as nitrogen gas.
3. Nitrogen fixation: Soil atmosphere contains up to 80% nitrogen. This nitrogen is oxidized to form nitrate ions by two groups of bacteria namely:
4. Symbiotic bacteria like Rhizobium leguminousarum. They live in root noodles of legumes. The bacteria obtain carbohydrates from the plant while the plant obtains nitrogen.
5. Free living bacteria like clostridium and azotobacter. The bacteria fix atmosphere nitrogen into the soil aerobically and anaerobically.
6. Addition of organic manure and nitrogen fertilizers also adds nitrogen to the soil when they decay.
7. Denitrification: This is the process by which nitrates in the soil are converted to nitrogen gas by certain denitrifying bacteria.

IMPORTANCE OF NITROGEN CYCLE

Nitrogen cycle is one of the most important nutrient cycle in relation to terrestrial ecosystem:

1. Nitrogen is required by organisms for metabolic function and respiration
2. It is useful to plants in form of a solid nitrate
3. Nitrogen is used in plant for the manufacture of food (protein).

CARBON CYCLE

This involves the process involved in the flow of carbon in the environment

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