Production of ammonia from ammonium-containing compounds
Include urea, proteins, nucleic acid and vitamins
Saprobiotic micro-organisms feed on these and release ammonia
Forms ammonium ions in soil
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Nitrification
Conversion of ammonium ions into nitrate ions
Happens in two stages
Oxidation of ammonium ions to nitrite ions
Oxidation of nitrite ions to nitrate ions
Nitrifying bacteria need oxygen to do these conversions
Need soil that has many air spaces
Raise productivity by ploughing
Drainage of soil also prevents waterlogged soil
Prevents air being forced out of the soil
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Nitrogen Fixation
Nitrogen gas converted into nitrogen-containing compounds
Most important form is carried out by micro-organisms
Free-living nitrogen-fixing bacteria- reduce gaseous nitrogen to ammonia- use to manufacture amino acids. Nitrogen-rich compounds released when they die and decay
Mutualistic nitrogen-fixing bacteria- live in nodules of roots of plants (e.g. beans and peas). Obtain CHO from plants and plant gains amino acids from bacteria
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Denitrification
Soil becomes waterlogged and short of oxygen
Type of micro-organism changes
Fewer aerobic nitrifying and nitrogen-fixing bacteria found
Increase in anaerobic dentrifying bacteria
Convert nitrates into gaseous nitrogen
Reduces availablity of nitrogen-containing compounds
Less uptake by plants
Cannot grow as much- productivity reduced
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The carbon cycle
Carbon dioxide is dissolved in the air and oceans
Carbon dioxide in the air diffuses into leaves of plants through stomata and is used in photosynthesis
These plants then either die or are eaten by consumers
If they die, saprobiotic micro-organisms secrete enzymes onto its surface and hydrolyse the carbon-containing compounds into soluble, small molecules. Absorbed by micro-organism and released to atmopshere through respiration and decay
If eaten, the carbon-containing compounds are passed to the consumers, who undergo the above process when they die
If decay is prevented, fossil fuels are formed and then burned for energy for human activity
Combustion of fossil fuels releases carbon dioxide back into the atmosphere
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