Nitrification
- Nitrifying bacteria oxidise ammonium ion to a nitrate
- NH4+ ⇒ NO2- ⇒ NO3-
Nitrogen fixation
- When nitrogen gas is reduced, converted into ammonia.
- The ammonia then dissolves in water, forming NH4+.
- This is done by free-living bacteria and mutualistic bacteria
Denitrification
- When anaerobic denitrifying bacteria covert soil nitrates into gaseous nitrogen
Leeching and Eutrophication.
This is the same if fertilisers are nitrate of phoshpates
- Farmers apply fertilisers in large quantities
- Nutrients build up in bodies of water due to them being washed from the soil, making algae grow faster.
- This blocks light so submerged plants can’t photosynthesise. They die
- Saprobiotic microorganisms breakdown dead plants
- These use up O2 due to respiration so less in the water
- Aerobic organisms therefore die (e.g fish)
Ammonification
- Saprobiotic microorganisms break down protein into ammonia
🔴️ Dead leaves contain starch. How do microorganism make Carbon in starch available to plants?
- Saprobiotic microorganisms release enzyme (extra cellular digestion).
- This converts starch into monosaccharides.
- The microorganisms absorbs then respires the glucose made, releasing CO2
- In photosynthesis the plants absorb CO2 through the stomata of the leaf
- Useful organic products e.g Glucose is made in calvin cycle
🔴️Advantages of using natural fertilisers
- Making artificial fertilisers uses energy so cheaper
- Less leeching and eutrophication as there is a slow release of nutrients
- Contains wider range of elements
- Aerates soil
🔴️Why do plants have a higher carbon:nitrogen ratio than animal
- Plants have cellulose in cell walls
- They contain starch in plant tissue
- More protein in animal cells (muscle)
🔴️How is the nitrogen in dead plants made available for other plants?
- Proteins are decomposed by Saprobiotic microorganisms
- Ammonia is formed
- NH4+ ⇒ NO2- ⇒ NO3- by nitrifying bacteria
- Nitrate can be absorbed by roots
🔴️Why does adding fertilisers increase the mass of crop?
- Replaces nitrates removed from the soil
- Fertilisers contain nitrate needed for protein production
- This leads to more growth as Nitrogen is in DNA
🔴️Advantages of artificial fertilisers
- Easy to apply and store
- Can supply to specific needs
- Easy to control mass
- Faster releases of ions and minerals
🔴️Why does a plant die if the leaves drastically diminish in size
- Less SA for light to be absrobed ]
- so less photosynthesis occurs
- Less glucose is made
- respiration rate > photosynthesis
Explain why there would be an increase in the diversity of birds as the woodland developed from a farmland
- Greater variety diversity of plants and insects
- Greater varieties of food;
- More habitats and niches available
Explain how human activities have contributed to global warming.
- Carbon dioxide is a greenhouse gas;
- Deforestation leads to less carbon dioxide removed by photosynthesis;
- Microorganisms decompose them respiring
- Combustion releases carbon dioxide;
- Methane is a greenhouse gas too
- This is released from livestock e.g rice fields and cattle;
How does ploughing increase soil fetility
- Since there is more oxygen, fewer denitrifying bacteria convert NO3 to N2.
- More nitrates are formed as more nitrifying bacteria can oxidise NH4+ to NO2
- There is also less competition among bacteria
How can application of high concentration of fertilisers affect plant growth?
- will lower water potential of soil
- so more water moves out by osmosis
- the plant will wilt as water is still lost via transpiration
Explain how including leguminous plants in a crop rotation reduces the need to use artificial fertilisers.
- contains nitrogen-fixing bacteria in nodules so don’t need fertiliser
- nitrogen containing compounds added to the soil when plant dies
Crop rotation involves growing different crops each year in the same field. How does this leads to high crop yields?
- Different crops have different pests
- Different crops use different nutrients and ions from the soil
- Lugiminous plants (Nitrogen fixing bacteria) can be grown, which increases the soil nitrate
If there is an increase in the total biomass of a forest, why does the gross productivity decrease?
- More competition for light
- Reduced rate of photosynthesis so less glucose made
Advantages of having leguminous plants
- Nitrogen fixing bacteria in root nodules
- N2⇒ NH4+
- NH4+ ⇒ NO2- ⇒ NO3- by nitrifying bacteria
- Less need for fertiliser;
- When they die nitrogen-containing compounds are released into the soil
Explain how the decay of dead plants results in reduced oxygen concentration and increased nitrate production
- saprobiotic micro decompose plants via extracellular digestion
- they converts proteins into ammonia
- microrganisms divide and respire;
- respiration uses up oxygen;
- nitrifying bacteria convert ammonium compounds to nitrates;
- nitrification uses oxygen;
How will reduced oxygen concentration of water change the composition of the communities in the river.
- lower species diversity
- species tolerant to low oxygen thrive
- species requiring high oxygen die out;
why does the application of very high concentrations of fertiliser to the soil causes plants to wilt.
- lowers water potential in soil
- plants lose water to soil by osmosis;
- plants still lose water by transpiration;
describe farming practices that results in more nitrogen-containing compounds in soil
- growing legumes
- ploughing
- adding cattle manure
- adding fertilisers
