All plants need mineral ions, especially nitrates from the soil
Intensive food production depletes the stores of ions
Mineral ions are removed and not replaced as the crops are sold or eaten and the livestock is sold
No decomposition returning the nutrients to the soil
Without replenishing the nutrients, nutrients will become the limiting factor
Natural (organic) fertiliser - dead and decaying organisms as well as animal waste e.g. manure
Artificial (inorganic) fertiliser - minerals are mined from rocks and are blended and converted into a blend with the appropriate balance of minerals needed
e.g. nitrogen is needed for amino acids, ATP and nucleotides
Therefore, places with more nitrate ions tend to have plants that grow quicker than normal and with bigger leaves and taller plants, more photosynthesis can happen increasing productivity
This makes food cheaper as more food can be produced
Use of fertilisers has doubled UK food production since 1995
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Effects of nitrogen-containing fertilisers
Reduced species diversity
Nitrogen-rich soils favour the growth of grasses, nettles and other rapidly growing species
They, therefore, outcompete other species which results in their death
Species-rich hay meadows only survive when nitrogen concentrations are low enough to allow other species to compete with grass
Leaching - can lead to pollution of watercourses
Leaching is the process where nutrients are removed from the soil
Rainwater can dissolve soluble nutrients such as nitrate ions
This takes the ions deep into the soil or into watercourses such as streams and rivers
Here, they can have a harmful effect on humans if the water is for drinking as it prevents efficient oxygen transportation in babies and can cause stomach cancer
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Eutrophication
Most lakes and rivers have a naturally low concentration of nitrate and so nitrate ions are the limiting factors for the growth of algae
As the nitrate ion concentration increases due to leaching, it is no longer the limiting factor
Algae grow rapidly on the surface - an algal bloom
The dense surface layer prevents light from going through
LIght is the limiting factor for plants beneath and the plants can't photosynthesise and die
Saprobiontic bacteria populations grow using the dead organisms as food
Saprobiontic bacteria require oxygen for respiration increasing the demand for oxygen
The concentration of oxygen decreases and nitrates are released from the dead organisms
There is no longer enough oxygen for fish to breathe so they die as the oxygen is used up
Without aerobic organisms, anaerobic organisms can thrive so their populations rise
They release toxic wastes such as hydrogen sulphide which makes the water putrid
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