The document discusses several topics related to food production and agricultural ecosystems: 1. Intensive food production places pressure on farmers to cut costs and use methods that impact the environment. There is a conflict between cheap food and environmental conservation. 2. Agricultural ecosystems differ from natural ecosystems in that they require additional energy inputs and have less species and genetic diversity due to human manipulation. 3. The use of nitrogen-containing fertilizers can increase food production but also leads to negative effects like reduced diversity, soil acidification, and water pollution if overapplied. Alternative practices aim to reduce nitrogen fertilizer use.

2. The need for cheap and plentiful food
As a consumer, the man is involved In the research for a wide range
of food at minimum cost. This research put the farmers under
pressure to cut costs and supply cheap food in order to stay in
business. So, they used intensive method of food production with its
consequent impact on the environment.
There is clearly a conflict between our wish for cheap and plentiful
food and our desire to conserve the environment.
The question is: how skilfully can we balance these two conflicting needs?

3. Agricultural ecosystems
Agricultural ecosystems are strongly artificially controlled by humans to prevent them
From reaching their natural climax communities, they’re maintained in an arrested state
called Plagioclimax.
They’re made up by largely of domestic animals and plants used to produce food for
humans.
Natural Ecosystem Agricultural Ecosystem
No additional energy input beyond solar energy Energy from food and fossils fuels needed in
addition to solar energy in order to maintain a
plagioclimax
Lower productivity Higher productivity
More species diversity Less species diversity
More genetic diversity between species Less genetic diversity within species that are
selectively bred or genetically engineered for a
narrow range of desirable characteristics
Nutrients ar recycled naturally within the Natural recycling of nutrients is often
ecosystem with little addition from outside supplemented by the addition of fertilisers.
Pupulations are controlled only by natural means Populations are controlled by both natural means
such as competition, climate, predation and and the use of other agents such as pesticides
diseases

4. Conflict between intensive food production and conservation
The increasing of food production is made up by the improved genetic varieties of plant
and animal species,
Greater use of chemical fertiliser and pesticides, greater use of biotechnology, and
changes in farm practices. These change have had many ecological impacts like the
diminish of the variety of habitats.
Certain practices have directly removed habitats and reduced species diversity
1. Removal of hedgerows and grubbing out woodland
2. Creating monocultures
3. Filling in ponds and draining marsh and other wetland
4. Over-grazing of land
But, there are many management techniques that can be applied in order to increase species
and habitat diversity without unduly raising food costs or lowering yields.

5. Examples of conservation techniques:
-Maintain existing hedgerows at the most beneficial height and shape.
-Plant hedges rather than erect fences as field boundaries.
-Maintain existing ponds and where possible create new ones.
-Leave wet corners of fields rather than draining them.
-Plant native trees on land with a low species diversity.
-Reduces the use of pesticides.
-Use organic fertilisers.
-Use crop rotation.
-Use intercropping to control weeds
-Create natural meadows.
-Leave the cutting of verges and fields edges , until after flowering and when seeds have dispe

6. USE & EFFECTS on ecosystems of
nitrogen-containing fertilisers

7. In natural ecosystems not all the minerals that are removed
from the soil by plants are returned. When the nutrient levels
of agricultural land are low, fertilisers need to be added to
the soil to offset the reduction in mineral ions.
CROPS FOR FOOD OR ANIMALS’S FORAGE NEED A LOT OF NUTRIENTS
IN THE SOIL, ESPECIALLY NITROGEN. WHERE FOOD PRODUCTION IS
INTENSIVE, IT IS USUALLY NECESSARY SUPPLYING NITROGEN TO THE
SOIL.
THIS CAN HAVE HARMFUL ECOLOGICAL CONSEQUENCES.
natural (organic) fertilisers: consist of
The fertilisers are the dead and decaying remains of
plants and animals as well as animal
of two types wastes (manure and bone meal)
artificial (inorganic) fertilisers: that are
mined from rocks and converted into
different forms and blended together to
give the appropriate balance of minerals

8. IT IS IMPORTANT THAT NUTRIENTS ARE ADDED IN APPROPRIATE QUANTITIES. INFACT THE
APPLICATION OF FERTILISER IS SUBJECT TO THE LAW OF DIMINISHING RETURNS, BECAUSE
AN OVERAPPLICATION CAN ACTUALLY REDUCE YIELD BECAUSE:
 high mineral levels, especially of nitrate, lead to rapid vegetative
growth. Plant grow tall and are easily flattened by wind or rain, with
subsequent reduction in photosynthesis
 where minerals and water are readily available, roots develop less
extensively, plants may be easily uprooted and germination and early
growth are slower
The law of diminishing returns:
after a certain level of fertilizers’s
input the yield drops

9. EFFECTS OF NITROGEN FERTILISERS
There can be no doubt that nitrogen fertilisers have been a considerable benefit in
providing us with food. It’s estimated that the use of fertilisers has increased agricultural
food production in the UK by around 100% since 1955.
But the additional use of nitrogen-containing fertilisers has also had some negative effects.
These include:
• reduced species diversity
• increased soil acidity
• pollution of drinking water
• eutrophications EUTROPHICATION BY FERTILISERS
It’s a natural process that occurs mostly in freshwater lakes and the lower reaches
of rivers; where eutrophication occurs the sequence of events is as follows:
• the higher concentration of salts encourages the growth of algae & this leads to
the water becoming densely populated with algae
• light don't penetrate to any depth and so plants at lower levels die
• the dead plants are quickly decomposed by saprobiontic bacteria; these bacteria
use up oxigen for aerobic respiration & consequential creating an increased
biochemical oxygen demand (BOD)
• a rise in BOD means a lower oxygen content of water and that's why organisms
such as fish die due to te lack of oxygen

10. ALTERNATIVES TO
NITROGEN-CONTAINING FERTILISERS
Practices that can be used to reduce the need to use nitrogen-containing
fertilisers including:
• crop rotation: by growing a different crop on a particular area of land each
year, soil fertility may be maintained and the risk of desease reduced;
• intercropping: based on a principle similar to crop rotation, with two or more
crops being grown together;
• growing genetically engineered varieties of a crop: they have had a nitrogen-
fixing gene introduced into them artificially

11. ADVANTAGES & DISADVANTAGES OF USING ORGANIC &INORGANIC FERTILISERS
advantages disadvantages
•supply all the necessary •not easily obtained
Natural nutrients for growth •bulky and therefore
•increase water retention of expensive to transport
(organic)
the soil •slow acting
fertilisers •effective over a long period •difficult to handle
•improve the crumb structure •may contain pathogens
of the soil •mineral content low and
variable
•quick acting •do not improve the soil’s
Artificial •easy to handle physical characteristics
(inorganic) •relatively cheap •can be easily removed by
•easily obtained leaching and so need to be
fertilisers
•do not spread desease regulary applied
•mineral contain can be •run-off can cause pollution of
adjusted water courses