| what does intensive farming include? | growing high yield crops
can involve the use of fertilisers and pesticides |
| what is the purpose of fertiliser | provide plants with chemicals such as nitrates which increase crop yield |
| what is the purpose of pesticides | kill plants and animals which reduce crop yield |
| how to nitrates increase crop yield | they dissolve in soil water and are absorbed into plants by plant roots
they are used by plants to make amino acids which are synthesised into protein in the plants |
| name an environmental disadvantage of using fertilisers | they can leach into fresh water, adding extra unwanted nitrates
this increases algal populations which causes algal blooms (excessively large numbers of algae)
algal blooms reduce light levels, killing aquatic plants below them in the water
these dead plants and dead algae become food for bacteria which increase greatly in number
the bacteria use up large quantities of oxygen, reducing the oxygen availability for other organisms
other organisms die |
| name an alternative to using fertiliser | genetically modified crops
for example, scientists have produced a genetically modified rice plant which can take up and use nitrogen from the soil more efficiently than varieties that are currently being grown |
| name a negative effect of pesticides | pesticides sprayed onto crops can accumulate in the bodies of organisms over time (they are not broken down in the body therefore are not excreted) - this is called bioaccumulation
as they are passed along food chains, toxicity (concentration of these toxic chemicals) increases and can reach lethal levels |
| what are some alternatives to pesticides | use biological control such as introducing a predator or parasite into the crop to eat the insect pests
use genetically modified crops as some can be made to be toxic to plants |
