6.4 Use of natural and artificial fertilisers
Agricultural ecosystems increase the efficiency of energy conversion along human food chains. They
do so by improving productivity. One farming practice that contributes to this improved productivity
is the use of fertilisers.
The need for fertilisers
All plants need mineral ions, particularly nitrogen, from the soil. Much food production in the
developed world is intensive (concentrated on specific areas of land that are used repeatedly to gain
maximum yield). Intensive food production makes large demands on the soil because mineral ions
are continually taken up by the crops being grown on it. These crops are either used directly as food
for humans or feed for animals that become food. Either way, the mineral ions that the crops have
absorbed from the soil are removed.
In natural ecosystems the minerals that are removed from the soil by plants are returned when the
plant is broken down by microorganisms once it has died. In agricultural ecosystems the crop is
harvested and then transported from its point of origin for consumption. The urine, faeces and dead
remains of the consumer are rarely returned to the same area of land. Under these conditions the
levels of the mineral ions in agricultural land will fall. It is therefore necessary to replenish these
mineral ions because; otherwise their reduced levels will become the main limiting factor to plant
growth. Productivity will consequently be reduced. To offset this loss of mineral ions, fertilisers need
to be added to the soil. These fertilisers can be one of two types:
Natural (organic) fertilisers – These consist of the dead and decaying remains of plants and
animals as well as animal waste such as manure and bone meal
Artificial (inorganic) fertilisers – These are mined from rocks and deposits and then
converted into different forms and blended together to give the right balance of minerals for
a particular crop. Compounds containing the elements potassium, nitrogen and
phosphorous are almost always used.
Research suggests that a combination of natural and artificial fertilisers give the greatest long term
increase in productivity. However, it is important that minerals are added in appropriate quantities
as there is a point at which increases in the amount of fertiliser no longer results in increased
productivity.
How fertilisers increase productivity
Plants require minerals for their growth. Nitrogen is an essential component of proteins and DNA.
Both are needed for plant growth. Where nitrates are readily available, plants are likely to develop
earlier, grow taller and have a greater leaf area. This increases the rate of photosynthesis and
improves crop productivity. There can be no doubt that nitrogen fertilisers have been of
considerable benefit in providing us with cheaper food. It is estimated that the use of fertilisers has
increased agricultural food production in the UK by around 100% since 1955.
Page 1 of 1
Agricultural ecosystems increase the efficiency of energy conversion along human food chains. They
do so by improving productivity. One farming practice that contributes to this improved productivity
is the use of fertilisers.
The need for fertilisers
All plants need mineral ions, particularly nitrogen, from the soil. Much food production in the
developed world is intensive (concentrated on specific areas of land that are used repeatedly to gain
maximum yield). Intensive food production makes large demands on the soil because mineral ions
are continually taken up by the crops being grown on it. These crops are either used directly as food
for humans or feed for animals that become food. Either way, the mineral ions that the crops have
absorbed from the soil are removed.
In natural ecosystems the minerals that are removed from the soil by plants are returned when the
plant is broken down by microorganisms once it has died. In agricultural ecosystems the crop is
harvested and then transported from its point of origin for consumption. The urine, faeces and dead
remains of the consumer are rarely returned to the same area of land. Under these conditions the
levels of the mineral ions in agricultural land will fall. It is therefore necessary to replenish these
mineral ions because; otherwise their reduced levels will become the main limiting factor to plant
growth. Productivity will consequently be reduced. To offset this loss of mineral ions, fertilisers need
to be added to the soil. These fertilisers can be one of two types:
Natural (organic) fertilisers – These consist of the dead and decaying remains of plants and
animals as well as animal waste such as manure and bone meal
Artificial (inorganic) fertilisers – These are mined from rocks and deposits and then
converted into different forms and blended together to give the right balance of minerals for
a particular crop. Compounds containing the elements potassium, nitrogen and
phosphorous are almost always used.
Research suggests that a combination of natural and artificial fertilisers give the greatest long term
increase in productivity. However, it is important that minerals are added in appropriate quantities
as there is a point at which increases in the amount of fertiliser no longer results in increased
productivity.
How fertilisers increase productivity
Plants require minerals for their growth. Nitrogen is an essential component of proteins and DNA.
Both are needed for plant growth. Where nitrates are readily available, plants are likely to develop
earlier, grow taller and have a greater leaf area. This increases the rate of photosynthesis and
improves crop productivity. There can be no doubt that nitrogen fertilisers have been of
considerable benefit in providing us with cheaper food. It is estimated that the use of fertilisers has
increased agricultural food production in the UK by around 100% since 1955.
Page 1 of 1
