fertilisers and eutrophication Flashcards
what is lost when crops are harvested
nutrients
what do crops take in form the soil
Crops take in minerals from the soil as they grow and use them to build their own tissues.
when crops are harvested what happens and what does this result in
When crops are harvested, they’re removed from the field where they’re grown rather
than being allowed to die and decompose there. This means the mineral ions that they
contain (e.g. phosphates and nitrates) are not returned to the soil by decomposers in the
nitro gen or phosphorus cycles.
what happens when animals or animal products are removed from the land
Phosphates and nitrates are also lost from the system when animals or animal products
are removed from the land. Animals eat grass and other plants, taking in their nutrients.
W hen they are taken elsewhere for slaughter or transferred to a different field, the
nutrients aren’t re placed through their remains or waste pro ducts.
how are lost nutrients replaced
Fertilisers are Added to Soils to Replace Lost Nutrients
what does adding fertiliser do
Adding fertiliser re places the lost minerals, so more energy from the ecosystem can be used for growth,
increasing the efficiency of energy transfer. Fertilisers can be artificial or natural.
artificial fertilisers are inorganic, what does this mean
Artificial fertilisers are inorganic — they contain pure
chemicals (e.g. ammonium nitrate) as powders or pellets
natural fertilisers are organic matter, what does this mean
Natural fertilisers are organic matter — they include
manure, composted vegetables, crop residues (the
parts left over after the harvest) and sewage sludge.
what issues are there with fertilisers
environmental issues
what can happen when more fertiliser than needed is applied
This c an lead to the fertilisers le aching into waterways.
what is leaching
leaching is when water-soluble compounds in the soil are washed away, e.g. by rain
or irrigation systems. They’re often washed into nearby ponds and rivers.
what can leaching result in
eutrophication
when is leaching more likely to occur
Leaching is more likely to occur if the fertiliser is applied just before heavy rainfall.
inorganic ions are relatively soluble, what does this mean
In organic ions in chemical fertilisers are relatively soluble. This means that excess minerals
that are not used immediately are more likely to leach into waterways. In natural fertilisers,
the nitrogen and phosphorus are still contained in organic molecules that need to be
decomposed by micro organisms before they can be absorbed by plants. This means that
their release into the soil for uptake by plants is more controlled, and leaching is less likely.
what is the leaching of phosphates less likely than
The leaching of phosphates is less likely than the leaching o f nitrates
because phosphates are less soluble in water.
