The Nitrogen Cycle Flashcards
What is the nitrogen cycle an excellent example of?
How interconnected natural processes can make a natural resource that is not very abundant continually satisfy the needs of living organisms by recycling what has been used
Why is nitrogen essential?
A component of many essential biological molecules
What carries out many of the processes in the nitrogen cycle?
Living organisms, bacteria
What are the reservoirs in the nitrogen cycle?
Atmosphere
Biosphere
Lithosphere
Hydrosphere
What are the main chemical forms of nitrogen in the atmosphere?
Nitrogen gas
Oxides of nitrogen
What are the main forms of nitrogen in the biosphere?
Living organisms- DNA, proteins (enzymes, hormones)
DOM- proteins (releases ammonia when decomposed)
What is ionisation? (nitrogen cycle)
Processes such as lightning and meteor trials provide the energy for atmospheric nitrogen and oxygen to react and produce oxides of nitrogen
What are the ways that atmospheric nitrogen can be transferred into other forms of nitrogen?
Ionisation
Nitrogen fixation (root nodule)
Nitrogen fixation (nitrifying bacteria)
How does dead organic matter turn into ammonium ions?
Ammonification
How do Ammonium ions turn into nitrites and nitrates?
Double oxidation
Oxidation by bacteria first to nitrites then nitrates
What two things can happen to nitrates?
Absorbed by plant roots
Denitrified bacteria return it to atmosphere
What is fixation? (nitrogen cycle)
When some microorganisms chemically reduce nitrogen to ammonia.
What are the types of bacteria involved in nitrogen fixation?
Free living bacteria in the soil- Azotobacter
Live symbiotically in root nodules of legumes- Rhizobium
How are food chains a part of the nitrogen cycle?
Nitrogen passes between organisms as amino acids and proteins in food
What is nitrification?
The oxidation of ammonium ion to nitrites, then nitrates by nitrifying bacteria in the soil
What are some examples of the oxidising bacteria in the nitrogen cycle?
Nitrosomonas- nitrites
Nitrobacter- Nitrates
What is denitrification?
Chemical reduction of nitrates in the soil to nitrogen and nitrogen oxides by denitrifying bacteria in the soil
What is an example of a denitrifying bacteria?
Pseudomonas
What is a result of denitrification?
A reduction in soil fertility
What conditions does denitrification occur under?
Anaerobic conditions
What is leaching?
High solubility of nitrates means they are easily leached up of the soil into water bodies where they act as nutrients for aquatic plants and algae
How does root absorption form part of the nitrogen cycle?
Plants absorb nitrogen as soluble ions mainly as nitrates but also ammonium ions
How does ammonification form part of the nitrogen cycle?
Amino groups in proteins are released as ammonium ions by the action of bacteria, fungi and detritivores as DOM is decomposed
What is the Haber process?
An industrial process for producing ammonia from nitrogen and hydrogen using an iron catalyst with high temp and pressure
What is the problem with the Haber process?
Artificial fixation of atmospheric nitrogen to ammonia require a lot of energy
What is the main purpose of the Haber process?
Manufacture agricultural fertilisers
What is the problem of using nitrate fertiliser in agriculture?
May increase leaching problems such as eutrophication if application by heavy rain are applied near a river
How can the nitrogen cycle be affected by field drainage?
Drainage make the field more aerobic
Increase number of aerobic nitrifying bacteria
Reducing number of anaerobic denitrifying bacteria
How can soil disturbances affect the nitrogen cycle?
Ploughing increases the rate of decomposition of DOM which releases more nitrogen oxides into the atmosphere
How can leguminous plants affect the nitrogen cycle?
May be grown to increase the levels of nitrogen compounds in the soil which can be absorb by plants
What are some examples of legumes?
Peas
Beans
Clover
How can pollution affect the Nitrogen cycle? (Combustion)
Oxides of nitrogen are released into atmosphere form combustion which may increase quantity of nitrates washed into the soil by rain
How will control of the combustion processes manage the nitrogen cycle?
Less use of fossil fuel means less NOx released (deliberate choice, depleted supply)
Adopting circular economy principle result in low temperature manufacturing process from living organisms instead of fossil fuels
How can the Nitrogen cycle be sustainably managed by controlling the release of NOX?
Can be reduced using post combustion processes such as catalytic converters and urea sprays
How can the nitrogen cycle be sustainably managed by managing biological waste?
Decomposition of bio waste releases ammonium ions and amino acids
Enzymes produced by bacteria remove amino groups which dissolve ammonium ions useful or problem depending on area
How does eutrophication occur?
May be washed into water bodies by run off or they may be deliberately dumped there. The ammonium is converted into nitrites and nitrates causing eutrophication
How can organic fertilisers be used?
Manure, sewage, food production waste can be used to increase nutrient and humus levels
They can be ploughed into the soil or applied to surface
May be composted aerobically or digested anaerobically before fertiliser application
Reduces bulk
What farming practices can be done to increase soil nitrate levels?
Cultivation of legume crops
Crop rotation
Minimal use of pesticides that harm soil biota
Control of nitrate leaching
Not applying fertilisers during rain or when rain is likely
Use of low solubility fertilisers (Urea)
Use of low tillage techniques to reduce soil disturbance
Uncultivated ‘buffer strips’ left along rivers
Minimal use of nitrate fertiliser where leaching into aquifers is likely
